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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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See an example

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

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1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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Steps in the literature review process.

• What is a literature review?
• Define your research question
• Determine inclusion and exclusion criteria
• Choose databases and search
• Review Results
• Synthesize Results
• Analyze Results
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• Artificial Intelligence (AI) Tools
• You may need to some exploratory searching of the literature to get a sense of scope, to determine whether you need to narrow or broaden your focus
• Identify databases that provide the most relevant sources, and identify relevant terms (controlled vocabularies) to add to your search strategy
• Finalize your research question
• Think about relevant dates, geographies (and languages), methods, and conflicting points of view
• Conduct searches in the published literature via the identified databases
• Check to see if this topic has been covered in other discipline's databases
• Examine the citations of on-point articles for keywords, authors, and previous research (via references) and cited reference searching.
• Save your search results in a citation management tool (such as Zotero, Mendeley or EndNote)
• De-duplicate your search results
• Make sure that you've found the seminal pieces -- they have been cited many times, and their work is considered foundational 
• Check with your professor or a librarian to make sure your search has been comprehensive
• Evaluate the strengths and weaknesses of individual sources and evaluate for bias, methodologies, and thoroughness
• Group your results in to an organizational structure that will support why your research needs to be done, or that provides the answer to your research question  
• Develop your conclusions
• Are there gaps in the literature?
• Where has significant research taken place, and who has done it?
• Is there consensus or debate on this topic?
• Which methodological approaches work best?
• For example: Background, Current Practices, Critics and Proponents, Where/How this study will fit in 
• Organize your citations and focus on your research question and pertinent studies
• Compile your bibliography

Note: The first four steps are the best points at which to contact a librarian. Your librarian can help you determine the best databases to use for your topic, assess scope, and formulate a search strategy.

Videos Tutorials about Literature Reviews

This 4.5 minute video from Academic Education Materials has a Creative Commons License and a British narrator.

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Research Process :: Step by Step

• Introduction
• Select Topic
• Identify Keywords
• Background Information
• Develop Research Questions
• Refine Topic
• Search Strategy
• Popular Databases
• Evaluate Sources
• Types of Periodicals
• Reading Scholarly Articles
• Primary & Secondary Sources
• Organize / Take Notes
• Writing & Grammar Resources
• Annotated Bibliography
• Literature Review
• Citation Styles
• Paraphrasing
• Privacy / Confidentiality
• Research Process
• Selecting Your Topic
• Identifying Keywords
• Gathering Background Info
• Evaluating Sources

Organize the literature review into sections that present themes or identify trends, including relevant theory. You are not trying to list all the material published, but to synthesize and evaluate it according to the guiding concept of your thesis or research question.  

What is a literature review?

A literature review is an account of what has been published on a topic by accredited scholars and researchers. Occasionally you will be asked to write one as a separate assignment, but more often it is part of the introduction to an essay, research report, or thesis. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries

A literature review must do these things:

• be organized around and related directly to the thesis or research question you are developing
• synthesize results into a summary of what is and is not known
• identify areas of controversy in the literature
• formulate questions that need further research

Ask yourself questions like these:

• What is the specific thesis, problem, or research question that my literature review helps to define?
• What type of literature review am I conducting? Am I looking at issues of theory? methodology? policy? quantitative research (e.g. on the effectiveness of a new procedure)? qualitative research (e.g., studies of loneliness among migrant workers)?
• What is the scope of my literature review? What types of publications am I using (e.g., journals, books, government documents, popular media)? What discipline am I working in (e.g., nursing psychology, sociology, medicine)?
• How good was my information seeking? Has my search been wide enough to ensure I've found all the relevant material? Has it been narrow enough to exclude irrelevant material? Is the number of sources I've used appropriate for the length of my paper?
• Have I critically analyzed the literature I use? Do I follow through a set of concepts and questions, comparing items to each other in the ways they deal with them? Instead of just listing and summarizing items, do I assess them, discussing strengths and weaknesses?
• Have I cited and discussed studies contrary to my perspective?
• Will the reader find my literature review relevant, appropriate, and useful?

Ask yourself questions like these about each book or article you include:

• Has the author formulated a problem/issue?
• Is it clearly defined? Is its significance (scope, severity, relevance) clearly established?
• Could the problem have been approached more effectively from another perspective?
• What is the author's research orientation (e.g., interpretive, critical science, combination)?
• What is the author's theoretical framework (e.g., psychological, developmental, feminist)?
• What is the relationship between the theoretical and research perspectives?
• Has the author evaluated the literature relevant to the problem/issue? Does the author include literature taking positions she or he does not agree with?
• In a research study, how good are the basic components of the study design (e.g., population, intervention, outcome)? How accurate and valid are the measurements? Is the analysis of the data accurate and relevant to the research question? Are the conclusions validly based upon the data and analysis?
• In material written for a popular readership, does the author use appeals to emotion, one-sided examples, or rhetorically-charged language and tone? Is there an objective basis to the reasoning, or is the author merely "proving" what he or she already believes?
• How does the author structure the argument? Can you "deconstruct" the flow of the argument to see whether or where it breaks down logically (e.g., in establishing cause-effect relationships)?
• In what ways does this book or article contribute to our understanding of the problem under study, and in what ways is it useful for practice? What are the strengths and limitations?
• How does this book or article relate to the specific thesis or question I am developing?

Text written by Dena Taylor, Health Sciences Writing Centre, University of Toronto

http://www.writing.utoronto.ca/advice/specific-types-of-writing/literature-review

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The Research Process: A Step-by-Step Guide

• Introduction
• Select Topic
• Identify Keywords
• Background Information
• Develop Research Questions
• Refine Topic
• Search Strategy
• Evaluate Sources
• Primary & Secondary Sources
• Types of Periodicals
• Organize / Take Notes
• Writing & Grammar Resources
• Annotated Bibliography

Literature Review

• Citation Styles
• Paraphrasing
• Privacy / Confidentiality
• How to Read Research Article
• ChatGPT and the Research Process

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Organize the literature review into sections that present themes or identify trends, including relevant theory. You are not trying to list all the material published, but to synthesize and evaluate it according to the guiding concept of your thesis or research question.  

What is a literature review?

A literature review is an account of what has been published on a topic by accredited scholars and researchers. Occasionally you will be asked to write one as a separate assignment, but more often it is part of the introduction to an essay, research report, or thesis. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries

A literature review must do these things:

• be organized around and related directly to the thesis or research question you are developing
• synthesize results into a summary of what is and is not known
• identify areas of controversy in the literature
• formulate questions that need further research

Ask yourself questions like these:

• What is the specific thesis, problem, or research question that my literature review helps to define?
• What type of literature review am I conducting? Am I looking at issues of theory? methodology? policy? quantitative research (e.g. on the effectiveness of a new procedure)? qualitative research (e.g., studies of loneliness among migrant workers)?
• What is the scope of my literature review? What types of publications am I using (e.g., journals, books, government documents, popular media)? What discipline am I working in (e.g., nursing psychology, sociology, medicine)?
• How good was my information seeking? Has my search been wide enough to ensure I've found all the relevant material? Has it been narrow enough to exclude irrelevant material? Is the number of sources I've used appropriate for the length of my paper?
• Have I critically analyzed the literature I use? Do I follow through a set of concepts and questions, comparing items to each other in the ways they deal with them? Instead of just listing and summarizing items, do I assess them, discussing strengths and weaknesses?
• Have I cited and discussed studies contrary to my perspective?
• Will the reader find my literature review relevant, appropriate, and useful?

Ask yourself questions like these about each book or article you include:

• Has the author formulated a problem/issue?
• Is it clearly defined? Is its significance (scope, severity, relevance) clearly established?
• Could the problem have been approached more effectively from another perspective?
• What is the author's research orientation (e.g., interpretive, critical science, combination)?
• What is the author's theoretical framework (e.g., psychological, developmental, feminist)?
• What is the relationship between the theoretical and research perspectives?
• Has the author evaluated the literature relevant to the problem/issue? Does the author include literature taking positions she or he does not agree with?
• In a research study, how good are the basic components of the study design (e.g., population, intervention, outcome)? How accurate and valid are the measurements? Is the analysis of the data accurate and relevant to the research question? Are the conclusions validly based upon the data and analysis?
• In material written for a popular readership, does the author use appeals to emotion, one-sided examples, or rhetorically-charged language and tone? Is there an objective basis to the reasoning, or is the author merely "proving" what he or she already believes?
• How does the author structure the argument? Can you "deconstruct" the flow of the argument to see whether or where it breaks down logically (e.g., in establishing cause-effect relationships)?
• In what ways does this book or article contribute to our understanding of the problem under study, and in what ways is it useful for practice? What are the strengths and limitations?
• How does this book or article relate to the specific thesis or question I am developing?

Text written by Dena Taylor, Health Sciences Writing Centre, University of Toronto

http://www.writing.utoronto.ca/advice/specific-types-of-writing/literature-review

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Literature Review

• What is a Literature Review?
• What is NOT a Literature Review?
• Purposes of a Literature Review
• Types of Literature Reviews
• Literature Reviews vs. Systematic Reviews
• Systematic vs. Meta-Analysis

Literature Review  is a comprehensive survey of the works published in a particular field of study or line of research, usually over a specific period of time, in the form of an in-depth, critical bibliographic essay or annotated list in which attention is drawn to the most significant works.

Also, we can define a literature review as the collected body of scholarly works related to a topic:

• Summarizes and analyzes previous research relevant to a topic
• Includes scholarly books and articles published in academic journals
• Can be an specific scholarly paper or a section in a research paper

The objective of a Literature Review is to find previous published scholarly works relevant to an specific topic

• Help gather ideas or information
• Keep up to date in current trends and findings
• Help develop new questions

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Helps focus your own research questions or problems
• Discovers relationships between research studies/ideas.
• Suggests unexplored ideas or populations
• Identifies major themes, concepts, and researchers on a topic.
• Tests assumptions; may help counter preconceived ideas and remove unconscious bias.
• Identifies critical gaps, points of disagreement, or potentially flawed methodology or theoretical approaches.
• Indicates potential directions for future research.

All content in this section is from Literature Review Research from Old Dominion University 

Keep in mind the following, a literature review is NOT:

Not an essay 

Not an annotated bibliography  in which you summarize each article that you have reviewed.  A literature review goes beyond basic summarizing to focus on the critical analysis of the reviewed works and their relationship to your research question.

Not a research paper   where you select resources to support one side of an issue versus another.  A lit review should explain and consider all sides of an argument in order to avoid bias, and areas of agreement and disagreement should be highlighted.

A literature review serves several purposes. For example, it

• provides thorough knowledge of previous studies; introduces seminal works.
• helps focus one’s own research topic.
• identifies a conceptual framework for one’s own research questions or problems; indicates potential directions for future research.
• suggests previously unused or underused methodologies, designs, quantitative and qualitative strategies.
• identifies gaps in previous studies; identifies flawed methodologies and/or theoretical approaches; avoids replication of mistakes.
• helps the researcher avoid repetition of earlier research.
• suggests unexplored populations.
• determines whether past studies agree or disagree; identifies controversy in the literature.
• tests assumptions; may help counter preconceived ideas and remove unconscious bias.

As Kennedy (2007) notes*, it is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the original studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally that become part of the lore of field. In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews.

Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are several approaches to how they can be done, depending upon the type of analysis underpinning your study. Listed below are definitions of types of literature reviews:

Argumentative Review      This form examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to to make summary claims of the sort found in systematic reviews.

Integrative Review      Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication.

Historical Review      Few things rest in isolation from historical precedent. Historical reviews are focused on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review      A review does not always focus on what someone said [content], but how they said it [method of analysis]. This approach provides a framework of understanding at different levels (i.e. those of theory, substantive fields, research approaches and data collection and analysis techniques), enables researchers to draw on a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection and data analysis, and helps highlight many ethical issues which we should be aware of and consider as we go through our study.

Systematic Review      This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyse data from the studies that are included in the review. Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?"

Theoretical Review      The purpose of this form is to concretely examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review help establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

* Kennedy, Mary M. "Defining a Literature."  Educational Researcher  36 (April 2007): 139-147.

All content in this section is from The Literature Review created by Dr. Robert Larabee USC

Robinson, P. and Lowe, J. (2015),  Literature reviews vs systematic reviews.  Australian and New Zealand Journal of Public Health, 39: 103-103. doi: 10.1111/1753-6405.12393

What's in the name? The difference between a Systematic Review and a Literature Review, and why it matters . By Lynn Kysh from University of Southern California

Systematic review or meta-analysis?

A  systematic review  answers a defined research question by collecting and summarizing all empirical evidence that fits pre-specified eligibility criteria.

A  meta-analysis  is the use of statistical methods to summarize the results of these studies.

Systematic reviews, just like other research articles, can be of varying quality. They are a significant piece of work (the Centre for Reviews and Dissemination at York estimates that a team will take 9-24 months), and to be useful to other researchers and practitioners they should have:

• clearly stated objectives with pre-defined eligibility criteria for studies
• explicit, reproducible methodology
• a systematic search that attempts to identify all studies
• assessment of the validity of the findings of the included studies (e.g. risk of bias)
• systematic presentation, and synthesis, of the characteristics and findings of the included studies

Not all systematic reviews contain meta-analysis. 

Meta-analysis is the use of statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review.  More information on meta-analyses can be found in  Cochrane Handbook, Chapter 9 .

A meta-analysis goes beyond critique and integration and conducts secondary statistical analysis on the outcomes of similar studies.  It is a systematic review that uses quantitative methods to synthesize and summarize the results.

An advantage of a meta-analysis is the ability to be completely objective in evaluating research findings.  Not all topics, however, have sufficient research evidence to allow a meta-analysis to be conducted.  In that case, an integrative review is an appropriate strategy. 

Some of the content in this section is from Systematic reviews and meta-analyses: step by step guide created by Kate McAllister.

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Literature reviews, what is a literature review, learning more about how to do a literature review.

• Planning the Review
• The Research Question
• Choosing Where to Search
• Organizing the Review
• Writing the Review

A literature review is a review and synthesis of existing research on a topic or research question. A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it relates to your research question. A literature review goes beyond a description or summary of the literature you have read. 

• Sage Research Methods Core Collection This link opens in a new window SAGE Research Methods supports research at all levels by providing material to guide users through every step of the research process. SAGE Research Methods is the ultimate methods library with more than 1000 books, reference works, journal articles, and instructional videos by world-leading academics from across the social sciences, including the largest collection of qualitative methods books available online from any scholarly publisher. – Publisher

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Literature Reviews

• What is a Literature Review?
• Six Steps to Writing a Literature Review
• Finding Articles
• Try A Citation Manager
• Avoiding Plagiarism

Selecting a Research Topic 

The first step in the process involves exploring and selecting a topic. You may revise the topic/scope of your research as you learn more from the literature. Be sure to select a topic that you are willing to work with for a considerable amount of time.

When thinking about a topic, it is important to consider the following: 

Does the topic interest you?

Working on something that doesn’t excite you will make the process tedious. The research content should reflect your passion for research so it is essential to research in your area of interest rather than choosing a topic that interests someone else. While developing your research topic, broaden your thinking and creativity to determine what works best for you. Consider an area of high importance to your profession, or identify a gap in the research. It may take some time to narrow down on a topic and get started, but it’s worth the effort.

Is the Topic Relevant?

Be sure your subject meets the assignment/research requirements. When in doubt, review the guidelines and seek clarification from your professor. 

What is the Scope and Purpose?

Sometimes your chosen topic may be too broad. To find direction, try limiting the scope and purpose of the research by identifying the concepts you wish to explore. Once this is accomplished, you can fine-tune your topic by experimenting with keyword searches our  A-Z Databases  until you are satisfied with your retrieval results.

Are there Enough Resources to Support Your Research? 

If the topic is too narrow, you may not be able to provide the depth of results needed. When selecting a topic make sure you have adequate material to help with the research. Explore a variety of resources: journals, books, and online information. 

Adapted from https://jgateplus.com/home/2018/10/11/the-dos-of-choosing-a-research-topic-part-1/

Why use keywords to search? 

• Library databases work differently than Google. Library databases work best when you search for concepts and keywords.
• For your research, you will want to brainstorm keywords related to your research question. These keywords can lead you to relevant sources that you can use to start your research project.
• Identify those terms relevant to your research and add 2-3 in the search box. 

Now its time to decide whether or not to incorporate what you have found into your literature review.  E valuate  your resources to make sure they contain information that is authoritative, reliable, relevant and the most useful in supporting your research.

Remember to be:

• Objective : keep an open mind
• Unbiased : Consider all viewpoints, and include all sides of an argument,  even ones that don't support your own

Criteria for Evaluating Research Publications

Significance and Contribution to the Field

• What is the author’s aim?

• To what extent has this aim been achieved?

• What does this text add to the body of knowledge? (theory, data and/or practical application)

• What relationship does it bear to other works in the field?

• What is missing/not stated?

• Is this a problem?

Methodology or Approach (Formal, research-based texts)

• What approach was used for the research? (eg; quantitative or qualitative, analysis/review of theory or current practice, comparative, case study, personal reflection etc…)

• How objective/biased is the approach?

• Are the results valid and reliable?

• What analytical framework is used to discuss the results?

Argument and Use of Evidence

• Is there a clear problem, statement or hypothesis?

• What claims are made?

• Is the argument consistent?

• What kinds of evidence does the text rely on?

• How valid and reliable is the evidence?

• How effective is the evidence in supporting the argument?

• What conclusions are drawn?

• Are these conclusions justified?

Writing Style and Text Structure

• Does the writing style suit the intended audience? (eg; expert/non-expert, academic/non- academic)

• What is the organizing principle of the text?

• Could it be better organized?

Prepared by Pam Mort, Lyn Hallion and Tracey Lee Downey, The Learning Centre © April 2005 The University of New South Wales. 

Analysis: the Starting Point for Further Analysis & Inquiry

After evaluating your retrieved sources you will be ready to explore both what has been  found  and what is  missing . Analysis involves breaking the study into parts,  understanding  each part, assessing the  strength  of evidence, and drawing  conclusions  about its relationship to your topic. 

Read through the information sources you have selected and try to analyze, understand and critique what you read.  Critically  review each source's methods, procedures, data validity/reliability, and other themes of interest.  Consider  how each source approaches your topic in addition to their collective points of  intersection  and  separation .  Offer an appraisal of past and current thinking, ideas, policies, and practices, identify gaps within the research, and place your current work and research within this wider discussion by considering how your research supports, contradicts, or departs from other scholars’ research and offer recommendations for future research.

Top 10 Tips for Analyzing the Research

• Define key terms
• Note key statistics 
• Determine emphasis, strengths & weaknesses
• Critique research methodologies used in the studies
• Distinguish between author opinion and actual results
• Identify major trends, patterns, categories, relationships, and inconsistencies
• Recognize specific aspects in the study that relate to your topic
• Disclose any gaps in the literature
• Stay focused on your topic
• Excluding landmark studies, use current, up-to-date sources

Prepared by the fine librarians at California State University Sacramento. 

Synthesis vs Summary

Your literature review should not simply be a summary of the articles, books, and other scholarly writings you find on your topic. It should synthesize the various ideas from your sources with your own observations to create a map of the scholarly conversation taking place about your research topics along with gaps or areas for further research.

Bringing together your review results is called synthesis. Synthesis relies heavily on pattern recognition and relationships or similarities between different phenomena. Recognizing these patterns and relatedness helps you make  creative connections  between previously unrelated research and identify any gaps.

As you read, you'll encounter various ideas, disagreements, methods, and perspectives which can be hard to organize in a meaningful way.  A  synthesis matrix  also known as a Literature Review Matrix is an effective and efficient method to organize your literature by recording the main points of each source and documenting how sources relate to each other. If you know how to make an Excel spreadsheet, you can create your own synthesis matrix, or use one of the templates below. 

Because a literature review is NOT a summary of these different sources, it can be very difficult to keep your research organized. It is especially difficult to organize the information in a way that makes the writing process simpler. One way that seems particularly helpful in organizing literature reviews is the synthesis matrix. Click on the link below for a short tutorial and synthesis matrix spreadsheet.

• Literature Review and Synthesis
• Lit Review Synthesis Matrix
• Synthesis Matrix Example

A literature review must include a thesis statement, which is your perception of the information found in the literature. 

A literature review: 

• Demonstrates your thorough  investigation  of and acquaintance with sources related to your topic
• Is not a simple listing, but a  critical discussion
• Must  compare  and  contrast  opinions
• Must  relate  your study to previous studies
• Must show  gaps  in research
• Can  focus  on a research question or a thesis
• Includes a  compilation  of the primary questions and subject areas involved
• Identifies  sources

https://custom-writing.org/blog/best-literature-review

Organizing Your Literature Review

The structure of the review is divided into three main parts—an introduction, body, and the conclusion.

Introduction

Discuss what is already known about your topic and what readers need to know in order to understand your literature review. 

• Scope, Method, Framework: ​ Explain your selection criteria and similarities between your sources. Be sure to mention any consistent methods, theoretical frameworks, or approaches.  
• Research Question or Problem Statement:  State the problem you are addressing and why it is important. Try to write your research question as a statement. 
• Thesis : Address the connections between your sources, current state of knowledge in the field, and consistent approaches to your topic. 
• Format:  Describe your literature review’s organization and adhere to it throughout.   

​ Body 

The discussion of your research and its importance to the literature should be presented in a logical structure.

• Chronological: Structure your discussion by the literature’s publication date moving from the oldest to the newest research. Discuss how your research relates to the literature and highlight any breakthroughs and any gaps in the research.
• Historical: Similar to the chronological structure, the historical structure allows for a discussion of concepts or themes and how they have evolved over time.
• Thematic: Identify and discuss the different themes present within the research. Make sure that you relate the themes to each other and to your research.
• Methodological: This type of structure is used to discuss not so much what is found but how. For example, an methodological approach could provide an analysis of research approaches, data collection or and analysis techniques.

Provide a concise summary of your review and provide suggestions for future research.

Writing for Your Audience 

Writing within your discipline means learning:

• the  specialized vocabulary  your discipline uses
• the rhetorical conventions and  discourse  of your discipline
• the research  methodologies  which are employed

Learn how to write in your discipline by  familiarizing  yourself with the journals and trade publications professionals, researchers, and scholars use. 

Use our Databases by Title  to access:

• The best journals
• The most widely circulated trade publications
• The additional ways professionals and researchers communicate, such as conferences, newsletters, or symposiums.
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How-to conduct a systematic literature review: A quick guide for computer science research

Angela carrera-rivera.

a Faculty of Engineering, Mondragon University

William Ochoa

Felix larrinaga.

b Design Innovation Center(DBZ), Mondragon University

Associated Data

• No data was used for the research described in the article.

Performing a literature review is a critical first step in research to understanding the state-of-the-art and identifying gaps and challenges in the field. A systematic literature review is a method which sets out a series of steps to methodically organize the review. In this paper, we present a guide designed for researchers and in particular early-stage researchers in the computer-science field. The contribution of the article is the following:

• • Clearly defined strategies to follow for a systematic literature review in computer science research, and
• • Algorithmic method to tackle a systematic literature review.

Graphical abstract

Specifications table

Method details

A Systematic Literature Review (SLR) is a research methodology to collect, identify, and critically analyze the available research studies (e.g., articles, conference proceedings, books, dissertations) through a systematic procedure [12] . An SLR updates the reader with current literature about a subject [6] . The goal is to review critical points of current knowledge on a topic about research questions to suggest areas for further examination [5] . Defining an “Initial Idea” or interest in a subject to be studied is the first step before starting the SLR. An early search of the relevant literature can help determine whether the topic is too broad to adequately cover in the time frame and whether it is necessary to narrow the focus. Reading some articles can assist in setting the direction for a formal review., and formulating a potential research question (e.g., how is semantics involved in Industry 4.0?) can further facilitate this process. Once the focus has been established, an SLR can be undertaken to find more specific studies related to the variables in this question. Although there are multiple approaches for performing an SLR ( [5] , [26] , [27] ), this work aims to provide a step-by-step and practical guide while citing useful examples for computer-science research. The methodology presented in this paper comprises two main phases: “Planning” described in section 2, and “Conducting” described in section 3, following the depiction of the graphical abstract.

Defining the protocol is the first step of an SLR since it describes the procedures involved in the review and acts as a log of the activities to be performed. Obtaining opinions from peers while developing the protocol, is encouraged to ensure the review's consistency and validity, and helps identify when modifications are necessary [20] . One final goal of the protocol is to ensure the replicability of the review.

Define PICOC and synonyms

The PICOC (Population, Intervention, Comparison, Outcome, and Context) criteria break down the SLR's objectives into searchable keywords and help formulate research questions [ 27 ]. PICOC is widely used in the medical and social sciences fields to encourage researchers to consider the components of the research questions [14] . Kitchenham & Charters [6] compiled the list of PICOC elements and their corresponding terms in computer science, as presented in Table 1 , which includes keywords derived from the PICOC elements. From that point on, it is essential to think of synonyms or “alike” terms that later can be used for building queries in the selected digital libraries. For instance, the keyword “context awareness” can also be linked to “context-aware”.

Planning Step 1 “Defining PICOC keywords and synonyms”.

Formulate research questions

Clearly defined research question(s) are the key elements which set the focus for study identification and data extraction [21] . These questions are formulated based on the PICOC criteria as presented in the example in Table 2 (PICOC keywords are underlined).

Research questions examples.

Select digital library sources

The validity of a study will depend on the proper selection of a database since it must adequately cover the area under investigation [19] . The Web of Science (WoS) is an international and multidisciplinary tool for accessing literature in science, technology, biomedicine, and other disciplines. Scopus is a database that today indexes 40,562 peer-reviewed journals, compared to 24,831 for WoS. Thus, Scopus is currently the largest existing multidisciplinary database. However, it may also be necessary to include sources relevant to computer science, such as EI Compendex, IEEE Xplore, and ACM. Table 3 compares the area of expertise of a selection of databases.

Planning Step 3 “Select digital libraries”. Description of digital libraries in computer science and software engineering.

Define inclusion and exclusion criteria

Authors should define the inclusion and exclusion criteria before conducting the review to prevent bias, although these can be adjusted later, if necessary. The selection of primary studies will depend on these criteria. Articles are included or excluded in this first selection based on abstract and primary bibliographic data. When unsure, the article is skimmed to further decide the relevance for the review. Table 4 sets out some criteria types with descriptions and examples.

Planning Step 4 “Define inclusion and exclusion criteria”. Examples of criteria type.

Define the Quality Assessment (QA) checklist

Assessing the quality of an article requires an artifact which describes how to perform a detailed assessment. A typical quality assessment is a checklist that contains multiple factors to evaluate. A numerical scale is used to assess the criteria and quantify the QA [22] . Zhou et al. [25] presented a detailed description of assessment criteria in software engineering, classified into four main aspects of study quality: Reporting, Rigor, Credibility, and Relevance. Each of these criteria can be evaluated using, for instance, a Likert-type scale [17] , as shown in Table 5 . It is essential to select the same scale for all criteria established on the quality assessment.

Planning Step 5 “Define QA assessment checklist”. Examples of QA scales and questions.

Define the “Data Extraction” form

The data extraction form represents the information necessary to answer the research questions established for the review. Synthesizing the articles is a crucial step when conducting research. Ramesh et al. [15] presented a classification scheme for computer science research, based on topics, research methods, and levels of analysis that can be used to categorize the articles selected. Classification methods and fields to consider when conducting a review are presented in Table 6 .

Planning Step 6 “Define data extraction form”. Examples of fields.

The data extraction must be relevant to the research questions, and the relationship to each of the questions should be included in the form. Kitchenham & Charters [6] presented more pertinent data that can be captured, such as conclusions, recommendations, strengths, and weaknesses. Although the data extraction form can be updated if more information is needed, this should be treated with caution since it can be time-consuming. It can therefore be helpful to first have a general background in the research topic to determine better data extraction criteria.

After defining the protocol, conducting the review requires following each of the steps previously described. Using tools can help simplify the performance of this task. Standard tools such as Excel or Google sheets allow multiple researchers to work collaboratively. Another online tool specifically designed for performing SLRs is Parsif.al 1 . This tool allows researchers, especially in the context of software engineering, to define goals and objectives, import articles using BibTeX files, eliminate duplicates, define selection criteria, and generate reports.

Build digital library search strings

Search strings are built considering the PICOC elements and synonyms to execute the search in each database library. A search string should separate the synonyms with the boolean operator OR. In comparison, the PICOC elements are separated with parentheses and the boolean operator AND. An example is presented next:

(“Smart Manufacturing” OR “Digital Manufacturing” OR “Smart Factory”) AND (“Business Process Management” OR “BPEL” OR “BPM” OR “BPMN”) AND (“Semantic Web” OR “Ontology” OR “Semantic” OR “Semantic Web Service”) AND (“Framework” OR “Extension” OR “Plugin” OR “Tool”

Gather studies

Databases that feature advanced searches enable researchers to perform search queries based on titles, abstracts, and keywords, as well as for years or areas of research. Fig. 1 presents the example of an advanced search in Scopus, using titles, abstracts, and keywords (TITLE-ABS-KEY). Most of the databases allow the use of logical operators (i.e., AND, OR). In the example, the search is for “BIG DATA” and “USER EXPERIENCE” or “UX” as a synonym.

Example of Advanced search on Scopus.

In general, bibliometric data of articles can be exported from the databases as a comma-separated-value file (CSV) or BibTeX file, which is helpful for data extraction and quantitative and qualitative analysis. In addition, researchers should take advantage of reference-management software such as Zotero, Mendeley, Endnote, or Jabref, which import bibliographic information onto the software easily.

Study Selection and Refinement

The first step in this stage is to identify any duplicates that appear in the different searches in the selected databases. Some automatic procedures, tools like Excel formulas, or programming languages (i.e., Python) can be convenient here.

In the second step, articles are included or excluded according to the selection criteria, mainly by reading titles and abstracts. Finally, the quality is assessed using the predefined scale. Fig. 2 shows an example of an article QA evaluation in Parsif.al, using a simple scale. In this scenario, the scoring procedure is the following YES= 1, PARTIALLY= 0.5, and NO or UNKNOWN = 0 . A cut-off score should be defined to filter those articles that do not pass the QA. The QA will require a light review of the full text of the article.

Performing quality assessment (QA) in Parsif.al.

Data extraction

Those articles that pass the study selection are then thoroughly and critically read. Next, the researcher completes the information required using the “data extraction” form, as illustrated in Fig. 3 , in this scenario using Parsif.al tool.

Example of data extraction form using Parsif.al.

The information required (study characteristics and findings) from each included study must be acquired and documented through careful reading. Data extraction is valuable, especially if the data requires manipulation or assumptions and inferences. Thus, information can be synthesized from the extracted data for qualitative or quantitative analysis [16] . This documentation supports clarity, precise reporting, and the ability to scrutinize and replicate the examination.

Analysis and Report

The analysis phase examines the synthesized data and extracts meaningful information from the selected articles [10] . There are two main goals in this phase.

The first goal is to analyze the literature in terms of leading authors, journals, countries, and organizations. Furthermore, it helps identify correlations among topic s . Even when not mandatory, this activity can be constructive for researchers to position their work, find trends, and find collaboration opportunities. Next, data from the selected articles can be analyzed using bibliometric analysis (BA). BA summarizes large amounts of bibliometric data to present the state of intellectual structure and emerging trends in a topic or field of research [4] . Table 7 sets out some of the most common bibliometric analysis representations.

Techniques for bibliometric analysis and examples.

Several tools can perform this type of analysis, such as Excel and Google Sheets for statistical graphs or using programming languages such as Python that has available multiple  data visualization libraries (i.e. Matplotlib, Seaborn). Cluster maps based on bibliographic data(i.e keywords, authors) can be developed in VosViewer which makes it easy to identify clusters of related items [18] . In Fig. 4 , node size is representative of the number of papers related to the keyword, and lines represent the links among keyword terms.

[1] Keyword co-relationship analysis using clusterization in vos viewer.

This second and most important goal is to answer the formulated research questions, which should include a quantitative and qualitative analysis. The quantitative analysis can make use of data categorized, labelled, or coded in the extraction form (see Section 1.6). This data can be transformed into numerical values to perform statistical analysis. One of the most widely employed method is frequency analysis, which shows the recurrence of an event, and can also represent the percental distribution of the population (i.e., percentage by technology type, frequency of use of different frameworks, etc.). Q ualitative analysis includes the narration of the results, the discussion indicating the way forward in future research work, and inferring a conclusion.

Finally, the literature review report should state the protocol to ensure others researchers can replicate the process and understand how the analysis was performed. In the protocol, it is essential to present the inclusion and exclusion criteria, quality assessment, and rationality beyond these aspects.

The presentation and reporting of results will depend on the structure of the review given by the researchers conducting the SLR, there is no one answer. This structure should tie the studies together into key themes, characteristics, or subgroups [ 28 ].

SLR can be an extensive and demanding task, however the results are beneficial in providing a comprehensive overview of the available evidence on a given topic. For this reason, researchers should keep in mind that the entire process of the SLR is tailored to answer the research question(s). This article has detailed a practical guide with the essential steps to conducting an SLR in the context of computer science and software engineering while citing multiple helpful examples and tools. It is envisaged that this method will assist researchers, and particularly early-stage researchers, in following an algorithmic approach to fulfill this task. Finally, a quick checklist is presented in Appendix A as a companion of this article.

CRediT author statement

Angela Carrera-Rivera: Conceptualization, Methodology, Writing-Original. William Ochoa-Agurto : Methodology, Writing-Original. Felix Larrinaga : Reviewing and Supervision Ganix Lasa: Reviewing and Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

Funding : This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant No. 814078.

Carrera-Rivera, A., Larrinaga, F., & Lasa, G. (2022). Context-awareness for the design of Smart-product service systems: Literature review. Computers in Industry, 142, 103730.

1 https://parsif.al/

Data Availability

State-of-the-art literature review methodology: A six-step approach for knowledge synthesis

• Original Article
• Open access
• Published: 05 September 2022
• Volume 11 , pages 281–288, ( 2022 )

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• Erin S. Barry   ORCID: orcid.org/0000-0003-0788-7153 1 , 2 ,
• Jerusalem Merkebu   ORCID: orcid.org/0000-0003-3707-8920 3 &
• Lara Varpio   ORCID: orcid.org/0000-0002-1412-4341 3  

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Introduction

Researchers and practitioners rely on literature reviews to synthesize large bodies of knowledge. Many types of literature reviews have been developed, each targeting a specific purpose. However, these syntheses are hampered if the review type’s paradigmatic roots, methods, and markers of rigor are only vaguely understood. One literature review type whose methodology has yet to be elucidated is the state-of-the-art (SotA) review. If medical educators are to harness SotA reviews to generate knowledge syntheses, we must understand and articulate the paradigmatic roots of, and methods for, conducting SotA reviews.

We reviewed 940 articles published between 2014–2021 labeled as SotA reviews. We (a) identified all SotA methods-related resources, (b) examined the foundational principles and techniques underpinning the reviews, and (c) combined our findings to inductively analyze and articulate the philosophical foundations, process steps, and markers of rigor.

In the 940 articles reviewed, nearly all manuscripts (98%) lacked citations for how to conduct a SotA review. The term “state of the art” was used in 4 different ways. Analysis revealed that SotA articles are grounded in relativism and subjectivism.

This article provides a 6-step approach for conducting SotA reviews. SotA reviews offer an interpretive synthesis that describes: This is where we are now. This is how we got here. This is where we could be going. This chronologically rooted narrative synthesis provides a methodology for reviewing large bodies of literature to explore why and how our current knowledge has developed and to offer new research directions.

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Avoid common mistakes on your manuscript.

Literature reviews play a foundational role in scientific research; they support knowledge advancement by collecting, describing, analyzing, and integrating large bodies of information and data [ 1 , 2 ]. Indeed, as Snyder [ 3 ] argues, all scientific disciplines require literature reviews grounded in a methodology that is accurate and clearly reported. Many types of literature reviews have been developed, each with a unique purpose, distinct methods, and distinguishing characteristics of quality and rigor [ 4 , 5 ].

Each review type offers valuable insights if rigorously conducted [ 3 , 6 ]. Problematically, this is not consistently the case, and the consequences can be dire. Medical education’s policy makers and institutional leaders rely on knowledge syntheses to inform decision making [ 7 ]. Medical education curricula are shaped by these syntheses. Our accreditation standards are informed by these integrations. Our patient care is guided by these knowledge consolidations [ 8 ]. Clearly, it is important for knowledge syntheses to be held to the highest standards of rigor. And yet, that standard is not always maintained. Sometimes scholars fail to meet the review’s specified standards of rigor; other times the markers of rigor have never been explicitly articulated. While we can do little about the former, we can address the latter. One popular literature review type whose methodology has yet to be fully described, vetted, and justified is the state-of-the-art (SotA) review.

While many types of literature reviews amalgamate bodies of literature, SotA reviews offer something unique. By looking across the historical development of a body of knowledge, SotA reviews delves into questions like: Why did our knowledge evolve in this way? What other directions might our investigations have taken? What turning points in our thinking should we revisit to gain new insights? A SotA review—a form of narrative knowledge synthesis [ 5 , 9 ]—acknowledges that history reflects a series of decisions and then asks what different decisions might have been made.

SotA reviews are frequently used in many fields including the biomedical sciences [ 10 , 11 ], medicine [ 12 , 13 , 14 ], and engineering [ 15 , 16 ]. However, SotA reviews are rarely seen in medical education; indeed, a bibliometrics analysis of literature reviews published in 14 core medical education journals between 1999 and 2019 reported only 5 SotA reviews out of the 963 knowledge syntheses identified [ 17 ]. This is not to say that SotA reviews are absent; we suggest that they are often unlabeled. For instance, Schuwirth and van der Vleuten’s article “A history of assessment in medical education” [ 14 ] offers a temporally organized overview of the field’s evolving thinking about assessment. Similarly, McGaghie et al. published a chronologically structured review of simulation-based medical education research that “reviews and critically evaluates historical and contemporary research on simulation-based medical education” [ 18 , p. 50]. SotA reviews certainly have a place in medical education, even if that place is not explicitly signaled.

This lack of labeling is problematic since it conceals the purpose of, and work involved in, the SotA review synthesis. In a SotA review, the author(s) collects and analyzes the historical development of a field’s knowledge about a phenomenon, deconstructs how that understanding evolved, questions why it unfolded in specific ways, and posits new directions for research. Senior medical education scholars use SotA reviews to share their insights based on decades of work on a topic [ 14 , 18 ]; their junior counterparts use them to critique that history and propose new directions [ 19 ]. And yet, SotA reviews are generally not explicitly signaled in medical education. We suggest that at least two factors contribute to this problem. First, it may be that medical education scholars have yet to fully grasp the unique contributions SotA reviews provide. Second, the methodology and methods of SotA reviews are poorly reported making this form of knowledge synthesis appear to lack rigor. Both factors are rooted in the same foundational problem: insufficient clarity about SotA reviews. In this study, we describe SotA review methodology so that medical educators can explicitly use this form of knowledge synthesis to further advance the field.

We developed a four-step research design to meet this goal, illustrated in Fig.  1 .

Four-step research design process used for developing a State-of-the-Art literature review methodology

Step 1: Collect SotA articles

To build our initial corpus of articles reporting SotA reviews, we searched PubMed using the strategy (″state of the art review″[ti] OR ″state of the art review*″) and limiting our search to English articles published between 2014 and 2021. We strategically focused on PubMed, which includes MEDLINE, and is considered the National Library of Medicine’s premier database of biomedical literature and indexes health professions education and practice literature [ 20 ]. We limited our search to 2014–2021 to capture modern use of SotA reviews. Of the 960 articles identified, nine were excluded because they were duplicates, erratum, or corrigendum records; full text copies were unavailable for 11 records. All articles identified ( n  = 940) constituted the corpus for analysis.

Step 2: Compile all methods-related resources

EB, JM, or LV independently reviewed the 940 full-text articles to identify all references to resources that explained, informed, described, or otherwise supported the methods used for conducting the SotA review. Articles that met our criteria were obtained for analysis.

To ensure comprehensive retrieval, we also searched Scopus and Web of Science. Additionally, to find resources not indexed by these academic databases, we searched Google (see Electronic Supplementary Material [ESM] for the search strategies used for each database). EB also reviewed the first 50 items retrieved from each search looking for additional relevant resources. None were identified. Via these strategies, nine articles were identified and added to the collection of methods-related resources for analysis.

Step 3: Extract data for analysis

In Step 3, we extracted three kinds of information from the 940 articles papers identified in Step 1. First, descriptive data on each article were compiled (i.e., year of publication and the academic domain targeted by the journal). Second, each article was examined and excerpts collected about how the term state-of-the-art review was used (i.e., as a label for a methodology in-and-of itself; as an adjective qualifying another type of literature review; as a term included in the paper’s title only; or in some other way). Finally, we extracted excerpts describing: the purposes and/or aims of the SotA review; the methodology informing and methods processes used to carry out the SotA review; outcomes of analyses; and markers of rigor for the SotA review.

Two researchers (EB and JM) coded 69 articles and an interrater reliability of 94.2% was achieved. Any discrepancies were discussed. Given the high interrater reliability, the two authors split the remaining articles and coded independently.

Step 4: Construct the SotA review methodology

The methods-related resources identified in Step 2 and the data extractions from Step 3 were inductively analyzed by LV and EB to identify statements and research processes that revealed the ontology (i.e., the nature of reality that was reflected) and the epistemology (i.e., the nature of knowledge) underpinning the descriptions of the reviews. These authors studied these data to determine if the synthesis adhered to an objectivist or a subjectivist orientation, and to synthesize the purposes realized in these papers.

To confirm these interpretations, LV and EB compared their ontology, epistemology, and purpose determinations against two expectations commonly required of objectivist synthesis methods (e.g., systematic reviews): an exhaustive search strategy and an appraisal of the quality of the research data. These expectations were considered indicators of a realist ontology and objectivist epistemology [ 21 ] (i.e., that a single correct understanding of the topic can be sought through objective data collection {e.g., systematic reviews [ 22 ]}). Conversely, the inverse of these expectations were considered indicators of a relativist ontology and subjectivist epistemology [ 21 ] (i.e., that no single correct understanding of the topic is available; there are multiple valid understandings that can be generated and so a subjective interpretation of the literature is sought {e.g., narrative reviews [ 9 ]}).

Once these interpretations were confirmed, LV and EB reviewed and consolidated the methods steps described in these data. Markers of rigor were then developed that aligned with the ontology, epistemology, and methods of SotA reviews.

Of the 940 articles identified in Step 1, 98% ( n  = 923) lacked citations or other references to resources that explained, informed, or otherwise supported the SotA review process. Of the 17 articles that included supporting information, 16 cited Grant and Booth’s description [ 4 ] consisting of five sentences describing the overall purpose of SotA reviews, three sentences noting perceived strengths, and four sentences articulating perceived weaknesses. This resource provides no guidance on how to conduct a SotA review methodology nor markers of rigor. The one article not referencing Grant and Booth used “an adapted comparative effectiveness research search strategy that was adapted by a health sciences librarian” [ 23 , p. 381]. One website citation was listed in support of this strategy; however, the page was no longer available in summer 2021. We determined that the corpus was uninformed by a cardinal resource or a publicly available methodology description.

In Step 2 we identified nine resources [ 4 , 5 , 24 , 25 , 26 , 27 , 28 ]; none described the methodology and/or processes of carrying out SotA reviews. Nor did they offer explicit descriptions of the ontology or epistemology underpinning SotA reviews. Instead, these resources provided short overview statements (none longer than one paragraph) about the review type [ 4 , 5 , 24 , 25 , 26 , 27 , 28 ]. Thus, we determined that, to date, there are no available methodology papers describing how to conduct a SotA review.

Step 3 revealed that “state of the art” was used in 4 different ways across the 940 articles (see Fig.  2 for the frequency with which each was used). In 71% ( n  = 665 articles), the phrase was used only in the title, abstract, and/or purpose statement of the article; the phrase did not appear elsewhere in the paper and no SotA methodology was discussed. Nine percent ( n  = 84) used the phrase as an adjective to qualify another literature review type and so relied entirely on the methodology of a different knowledge synthesis approach (e.g., “a state of the art systematic review [ 29 ]”). In 5% ( n  = 52) of the articles, the phrase was not used anywhere within the article; instead, “state of the art” was the type of article within a journal. In the remaining 15% ( n  = 139), the phrase denoted a specific methodology (see ESM for all methodology articles). Via Step 4’s inductive analysis, the following foundational principles of SotA reviews were developed: (1) the ontology, (2) epistemology, and (3) purpose of SotA reviews.

Four ways the term “state of the art” is used in the corpus and how frequently each is used

Ontology of SotA reviews: Relativism

SotA reviews rest on four propositions:

The literature addressing a phenomenon offers multiple perspectives on that topic (i.e., different groups of researchers may hold differing opinions and/or interpretations of data about a phenomenon).

The reality of the phenomenon itself cannot be completely perceived or understood (i.e., due to limitations [e.g., the capabilities of current technologies, a research team’s disciplinary orientation] we can only perceive a limited part of the phenomenon).

The reality of the phenomenon is a subjective and inter-subjective construction (i.e., what we understand about a phenomenon is built by individuals and so their individual subjectivities shape that understanding).

The context in which the review was conducted informs the review (e.g., a SotA review of literature about gender identity and sexual function will be synthesized differently by researchers in the domain of gender studies than by scholars working in sex reassignment surgery).

As these propositions suggest, SotA scholars bring their experiences, expectations, research purposes, and social (including academic) orientations to bear on the synthesis work. In other words, a SotA review synthesizes the literature based on a specific orientation to the topic being addressed. For instance, a SotA review written by senior scholars who are experts in the field of medical education may reflect on the turning points that have shaped the way our field has evolved the modern practices of learner assessment, noting how the nature of the problem of assessment has moved: it was first a measurement problem, then a problem that embraced human judgment but needed assessment expertise, and now a whole system problem that is to be addressed from an integrated—not a reductionist—perspective [ 12 ]. However, if other scholars were to examine this same history from a technological orientation, learner assessment could be framed as historically constricted by the media available through which to conduct assessment, pointing to how artificial intelligence is laying the foundation for the next wave of assessment in medical education [ 30 ].

Given these foundational propositions, SotA reviews are steeped in a relativist ontology—i.e., reality is socially and experientially informed and constructed, and so no single objective truth exists. Researchers’ interpretations reflect their conceptualization of the literature—a conceptualization that could change over time and that could conflict with the understandings of others.

Epistemology of SotA reviews: Subjectivism

SotA reviews embrace subjectivism. The knowledge generated through the review is value-dependent, growing out of the subjective interpretations of the researcher(s) who conducted the synthesis. The SotA review generates an interpretation of the data that is informed by the expertise, experiences, and social contexts of the researcher(s). Furthermore, the knowledge developed through SotA reviews is shaped by the historical point in time when the review was conducted. SotA reviews are thus steeped in the perspective that knowledge is shaped by individuals and their community, and is a synthesis that will change over time.

Purpose of SotA reviews

SotA reviews create a subjectively informed summary of modern thinking about a topic. As a chronologically ordered synthesis, SotA reviews describe the history of turning points in researchers’ understanding of a phenomenon to contextualize a description of modern scientific thinking on the topic. The review presents an argument about how the literature could be interpreted; it is not a definitive statement about how the literature should or must be interpreted. A SotA review explores: the pivotal points shaping the historical development of a topic, the factors that informed those changes in understanding, and the ways of thinking about and studying the topic that could inform the generation of further insights. In other words, the purpose of SotA reviews is to create a three-part argument: This is where we are now in our understanding of this topic. This is how we got here. This is where we could go next.

The SotA methodology

Based on study findings and analyses, we constructed a six-stage SotA review methodology. This six-stage approach is summarized and guiding questions are offered in Tab.  1 .

Stage 1: Determine initial research question and field of inquiry

In Stage 1, the researcher(s) creates an initial description of the topic to be summarized and so must determine what field of knowledge (and/or practice) the search will address. Knowledge developed through the SotA review process is shaped by the context informing it; thus, knowing the domain in which the review will be conducted is part of the review’s foundational work.

Stage 2: Determine timeframe

This stage involves determining the period of time that will be defined as SotA for the topic being summarized. The researcher(s) should engage in a broad-scope overview of the literature, reading across the range of literature available to develop insights into the historical development of knowledge on the topic, including the turning points that shape the current ways of thinking about a topic. Understanding the full body of literature is required to decide the dates or events that demarcate the timeframe of now in the first of the SotA’s three-part argument: where we are now . Stage 2 is complete when the researcher(s) can explicitly justify why a specific year or event is the right moment to mark the beginning of state-of-the-art thinking about the topic being summarized.

Stage 3: Finalize research question(s) to reflect timeframe

Based on the insights developed in Stage 2, the researcher(s) will likely need to revise their initial description of the topic to be summarized. The formal research question(s) framing the SotA review are finalized in Stage 3. The revised description of the topic, the research question(s), and the justification for the timeline start year must be reported in the review article. These are markers of rigor and prerequisites for moving to Stage 4.

Stage 4: Develop search strategy to find relevant articles

In Stage 4, the researcher(s) develops a search strategy to identify the literature that will be included in the SotA review. The researcher(s) needs to determine which literature databases contain articles from the domain of interest. Because the review describes how we got here , the review must include literature that predates the state-of-the-art timeframe, determined in Stage 2, to offer this historical perspective.

Developing the search strategy will be an iterative process of testing and revising the search strategy to enable the researcher(s) to capture the breadth of literature required to meet the SotA review purposes. A librarian should be consulted since their expertise can expedite the search processes and ensure that relevant resources are identified. The search strategy must be reported (e.g., in the manuscript itself or in a supplemental file) so that others may replicate the process if they so choose (e.g., to construct a different SotA review [and possible different interpretations] of the same literature). This too is a marker of rigor for SotA reviews: the search strategies informing the identification of literature must be reported.

Stage 5: Analyses

The literature analysis undertaken will reflect the subjective insights of the researcher(s); however, the foundational premises of inductive research should inform the analysis process. Therefore, the researcher(s) should begin by reading the articles in the corpus to become familiar with the literature. This familiarization work includes: noting similarities across articles, observing ways-of-thinking that have shaped current understandings of the topic, remarking on assumptions underpinning changes in understandings, identifying important decision points in the evolution of understanding, and taking notice of gaps and assumptions in current knowledge.

The researcher(s) can then generate premises for the state-of-the-art understanding of the history that gave rise to modern thinking, of the current body of knowledge, and of potential future directions for research. In this stage of the analysis, the researcher(s) should document the articles that support or contradict their premises, noting any collections of authors or schools of thinking that have dominated the literature, searching for marginalized points of view, and studying the factors that contributed to the dominance of particular ways of thinking. The researcher(s) should also observe historical decision points that could be revisited. Theory can be incorporated at this stage to help shape insights and understandings. It should be highlighted that not all corpus articles will be used in the SotA review; instead, the researcher(s) will sample across the corpus to construct a timeline that represents the seminal moments of the historical development of knowledge.

Next, the researcher(s) should verify the thoroughness and strength of their interpretations. To do this, the researcher(s) can select different articles included in the corpus and examine if those articles reflect the premises the researcher(s) set out. The researcher(s) may also seek out contradictory interpretations in the literature to be sure their summary refutes these positions. The goal of this verification work is not to engage in a triangulation process to ensure objectivity; instead, this process helps the researcher(s) ensure the interpretations made in the SotA review represent the articles being synthesized and respond to the interpretations offered by others. This is another marker of rigor for SotA reviews: the authors should engage in and report how they considered and accounted for differing interpretations of the literature, and how they verified the thoroughness of their interpretations.

Stage 6: Reflexivity

Given the relativist subjectivism of a SotA review, it is important that the manuscript offer insights into the subjectivity of the researcher(s). This reflexivity description should articulate how the subjectivity of the researcher(s) informed interpretations of the data. These reflections will also influence the suggested directions offered in the last part of the SotA three-part argument: where we could go next. This is the last marker of rigor for SotA reviews: researcher reflexivity must be considered and reported.

SotA reviews have much to offer our field since they provide information on the historical progression of medical education’s understanding of a topic, the turning points that guided that understanding, and the potential next directions for future research. Those future directions may question the soundness of turning points and prior decisions, and thereby offer new paths of investigation. Since we were unable to find a description of the SotA review methodology, we inductively developed a description of the methodology—including its paradigmatic roots, the processes to be followed, and the markers of rigor—so that scholars can harness the unique affordances of this type of knowledge synthesis.

Given their chronology- and turning point-based orientation, SotA reviews are inherently different from other types of knowledge synthesis. For example, systematic reviews focus on specific research questions that are narrow in scope [ 32 , 33 ]; in contrast, SotA reviews present a broader historical overview of knowledge development and the decisions that gave rise to our modern understandings. Scoping reviews focus on mapping the present state of knowledge about a phenomenon including, for example, the data that are currently available, the nature of that data, and the gaps in knowledge [ 34 , 35 ]; conversely, SotA reviews offer interpretations of the historical progression of knowledge relating to a phenomenon centered on significant shifts that occurred during that history. SotA reviews focus on the turning points in the history of knowledge development to suggest how different decisions could give rise to new insights. Critical reviews draw on literature outside of the domain of focus to see if external literature can offer new ways of thinking about the phenomenon of interest (e.g., drawing on insights from insects’ swarm intelligence to better understand healthcare team adaptation [ 36 ]). SotA reviews focus on one domain’s body of literature to construct a timeline of knowledge development, demarcating where we are now, demonstrating how this understanding came to be via different turning points, and offering new research directions. Certainly, SotA reviews offer a unique kind of knowledge synthesis.

Our six-stage process for conducting these reviews reflects the subjectivist relativism that underpins the methodology. It aligns with the requirements proposed by others [ 24 , 25 , 26 , 27 ], what has been written about SotA reviews [ 4 , 5 ], and the current body of published SotA reviews. In contrast to existing guidance [ 4 , 5 , 20 , 21 , 22 , 23 ], our description offers a detailed reporting of the ontology, epistemology, and methodology processes for conducting the SotA review.

This explicit methodology description is essential since many academic journals list SotA reviews as an accepted type of literature review. For instance, Educational Research Review [ 24 ], the American Academy of Pediatrics [ 25 ], and Thorax all lists SotA reviews as one of the types of knowledge syntheses they accept [ 27 ]. However, while SotA reviews are valued by academia, guidelines or specific methodology descriptions for researchers to follow when conducting this type of knowledge synthesis are conspicuously absent. If academics in general, and medical education more specifically, are to take advantage of the insights that SotA reviews can offer, we need to rigorously engage in this synthesis work; to do that, we need clear descriptions of the methodology underpinning this review. This article offers such a description. We hope that more medical educators will conduct SotA reviews to generate insights that will contribute to further advancing our field’s research and scholarship.

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Acknowledgements

We thank Rhonda Allard for her help with the literature review and compiling all available articles. We also want to thank the PME editors who offered excellent development and refinement suggestions that greatly improved this manuscript.

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40037_2022_725_moesm1_esm.docx.

For information regarding the search strategy to develop the corpus and search strategy for confirming capture of any available State of the Art review methodology descriptions. Additionally, a list of the methodology articles found through the search strategy/corpus is included

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Barry, E.S., Merkebu, J. & Varpio, L. State-of-the-art literature review methodology: A six-step approach for knowledge synthesis. Perspect Med Educ 11 , 281–288 (2022). https://doi.org/10.1007/s40037-022-00725-9

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DOI : https://doi.org/10.1007/s40037-022-00725-9

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Why do a literature review?

The Literature Review will place your research in context. It will help you and your readers:  

Locate patterns, relationships, connections, agreements, disagreements, & gaps in understanding Identify methodological and theoretical foundations Identify landmark and exemplary works Situate your voice in a broader conversation with other writers, thinkers, and scholars

The Literature Review will aid your research process. It will help you to:

Establish your knowledge Understand what has been said Define your questions Establish a relevant methodology Refine your voice Situate your voice in the conversation

What does a literature review look like?

The Literature Review structure and organization may include sections such as:  

An introduction or overview A body or organizational sub-divisions A conclusion or an explanation of significance

The body of a literature review may be organized in several ways, including:

Chronologically: organized by date of publication Methodologically: organized by type of research method used Thematically: organized by concept, trend, or theme Ideologically: organized by belief, ideology, or school of thought

• Find a focus
• Find models
• Review your target publication
• Track citations
• Read critically
• Manage your citations
• Ask friends, faculty, and librarians

Additional Sources

• Reviewing the literature. Project Planner.
• Literature Review: By UNC Writing Center
• PhD on Track
• CU Graduate Students Thesis & Dissertation Guidance
• CU Honors Thesis Guidance

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Graduate Research: Guide to the Literature Review

• "Literature review" defined
• Research Communication Graphic
• Literature Review Steps
• Search techniques
• Finding Additional "Items
• Evaluating information
• Citing Styles
• Ethical Use of Information
• Research Databases This link opens in a new window
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• Reading a Scholarly Article
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Introduction to Research Process: Literature Review Steps

When seeking information for a literature review or for any purpose, it helps to understand information-seeking as a process that you can follow. 5 Each of the six (6) steps has its own section in this web page with more detail. Do (and re-do) the following six steps:

1. Define your topic. The first step is defining your task -- choosing a topic and noting the questions you have about the topic. This will provide a focus that guides your strategy in step II and will provide potential words to use in searches in step III.

2. Develop a strategy. Strategy involves figuring out where the information might be and identifying the best tools for finding those types of sources. The strategy section identifies specific types of research databases to use for specific purposes.

3. Locate the information . In this step, you implement the strategy developed in II in order to actually locate specific articles, books, technical reports, etc.

4. Use and Evaluate the information. Having located relevant and useful material, in step IV you read and analyze the items to determine whether they have value for your project and credibility as sources.

5. Synthesize. In step V, you will make sense of what you've learned and demonstrate your knowledge. You will thoroughly understand, organize and integrate the information --become knowledgeable-- so that you are able to use your own words to support and explain your research project and its relationship to existing research by others.

6. Evaluate your work. At every step along the way, you should evaluate your work. However, this final step is a last check to make sure your work is complete and of high quality.

Continue below to begin working through the process.

5. Eisenberg, M. B., & Berkowitz, R. E. (1990). Information Problem-Solving: the Big Six Skills Approach to Library & Information Skills Instruction . Norwood, NJ: Ablex Publishing.

1. Define your topic.

I. Define your topic

A.  Many students have difficulty selecting a topic. You want to find a topic you find interesting and will enjoy learning more about.

B.   Students often select a topic that is too broad.  You may have a broad topic in mind initially and will need to narrow it.

1. To help narrow a broad topic :

a. Brainstorm.  

1). Try this technique for brainstorming to narrow your focus.   

a) Step 1.  Write down your broad topic.

b) Step 2. Write down a "specific kind" or "specific aspect" of the topic you identified in step 1.  

c) Step 3. Write down an aspect  --such as an attribute or behavior-- of the "specific kind" you identified in step 2.  

d) Step 4.  Continue to add  levels of specificity as needed to get to a focus that is manageable. However, you may want to begin researching the literature before narrowing further to give yourself the opportunity to explore what others are doing and how that might impact the direction that you take for your own research.                     

2) Three examples of using the narrowing technique. These examples start with very, very broad topics, so the topic at step 3 or 4 in these examples would be used for a preliminary search in the literature in order to identify a more specific focus.  Greater specificity than level 3 or 4 will ultimately be necessary for developing a specific research question. And we may discover in our preliminary research that we need to alter the direction that we originally were taking.

a) Example 1.      

             Step 1. information security

                      Step  2. protocols

                              Step 3.  handshake protocol

            Brainstorming has brought us to focus on the handshake protocol.

b) Example 2.  

            Step 1. information security

                     Step 2. single sign-on authentication

                              Step 3.  analyzing

                                       Step 4. methods

            Brainstorming has brought us to focus on methods for analyzing the security of single sign-on authentication

c) Example 3.  The diagram below is an example using the broad topic of "software" to show two potential ways to begin to narrow the topic. 

C. Once you have completed the brainstorming process and your topic is more focused, you can do preliminary research to help you identify a specific research question . 

1) Examine overview sources such as subject-specific encyclopedias and textbooks that are likely to break down your specific topic into sub-topics and to highlight core issues that could serve as possible research questions. [See section II. below on developing a strategy to learn how to find these encyclopedias]

2). Search the broad topic in a research database that includes scholarly journals and professional magazines (to find technical and scholarly articles) and scan recent article titles for ideas. [See section II. below on developing a strategy to learn how to find trade and scholarly journal articles]

D. Once you have identified a research question or questions, ask yourself what you need to know to answer the questions. For example,

1. What new knowledge do I need to gain?

2. What has already been answered by prior research of other scholars?

E.  Use the answers to the questions in C. to identify what words  to use to describe the topic when you are doing searches.

1. Identify key words

a.  For example , if you are investigating "security audits in banking", key terms to combine in your searches would be: security, audits, banking.

2.  Create a list of alternative ways of referring to a key word or phrase

a.For example , "information assurance" may be referred to in various ways such as: "information assurance," "information security," and "computer security."

b. Use these alternatives when doing searches.

3. As you are searching, pay attention to how others are writing about the topic and add new words or phrases to your searches if appropriate.

2. Develop a strategy.

II. Develop a strategy for finding the information. 

A. Start by considering what types of source might contain the information you need .  Do you need a dictionary for definitions? a directory for an address? the history of a concept or technique that might be in a book or specialized encyclopedia? today's tech news in an online tech magazine or newspaper?  current research in a journal article? background information that might be in a specialized encyclopedia? data or statistics from a specific organization or website?  Note that you will typically have online access to these source types.

B. This section provides a description of some of the common types of information needed for research.  

1. For technical and business analysis , look for articles in technical and trade magazines . These articles are written by information technology professionals to help other IT professionals do their jobs better. Content might include news on new developments in hardware or software, techniques, tools, and practical advice. Technical journals are also likely to have product ads relevant to information technology workers and to have job ads. Examples iof technical magazines include Network Computing and IEEE Spectrum .

2. To read original research studies , look for articles in scholarly journals and conference proceedings . They will provide articles written by  information technology professionals who are reporting original research; that is, research that has been done by the authors and is being reported for the first time. The audience for original research articles is other information technology scholars and professionals. Examples of scholarly journals include Journal of Applied Security Research , Journal of Management Information Systems , IEEE Transactions on Computers , and ACM Transactions on Information and System Security .

3. For original research being reported to funding agencies , look for technical reports on agency websites. Technical reports are researcher reports to funding agencies about progress on or completion of research funded by the agency.

4. For in-depth, comprehensive information on a topic , look for book-length volumes . All chapters in the book might be written by the same author(s) or might be a collection of separate papers written by different authors.

5. To learn about an unfamiliar topic , use textbooks ,  specialized encyclopedias and handbooks to get get overviews of topics, history/background, and key issues explained.

6. For instructions for hardware, software, networking, etc., look for manuals  that provide step-by-step instructions.

7. For technical details about inventions (devices, instruments, machines), look for patent documents .

C.   NOTE -  In order to search for and find original research studies,  it will help if you  understand  how information is produced, packaged  and  communicated  within your profession. This is explained in the tab  "Research Communication: Graphic."

3. Locate the information.

III. Locate the information

A. Use search tools designed to find the sources you want.  Types of sources were described in section II. above. 

Always feel free to Ask a librarian for assistance when you have questions about where and how locate the information you need.

B. Evaluate the search results (no matter where you find the information)

1. Evaluate the items you find using at least these 5 criteria:

a. accuracy -- is the information reliable and error free?

1) Is there an editor or someone who verifies/checks the information?

2) Is there adequate documentation: bibliography, footnotes, credits?

3) Are the conclusions justified by the information presented?

b. authority -- is the source of the information reputable?

1) How did you find the source of information: an index to edited/peer-reviewed material, in a bibliography from a published article, etc.?

2) What type of source is it: sensationalistic, popular, scholarly?

c. objectivity -- does the information show bias?

1) What is the purpose of the information: to inform, persuade, explain, sway opinion, advertise?

2) Does the source show political or cultural biases?

d. currency -- is the information current? does it cover the time period you need?

e. coverage -- does it provide the evidence or information you need?

2. Is the search producing the material you need? -- the right content? the right quality? right time period? right geographical location? etc. If not, are you using

a. the right sources?

b. the right tools to get to the sources?

c. are you using the right words to describe the topic?

3. Have you discovered additional terms that should be searched? If so, search those terms.

4. Have you discovered additional questions you need to answer? If so, return to section A above to begin to answer new questions.

4. Use and evaluate the information.

IV. Use the information.

A. Read, hear or view the source

1. Evaluate: Does the material answer your question(s)? -- right content? If not, return to B.

2. Evaluate: Is the material appropriate? -- right quality? If not, return to B.

B. Extract the information from the source : copy/download information, take notes, record citation, keep track of items using a citation manager.

1. Note taking (these steps will help you when you begin to write your thesis and/or document your project.):

a. Write the keywords you use in your searches to avoid duplicating previous searches if you return to search a research database again. Keeping track of keywords used will also save you time if your search is interrupted or you need return and do the search again for some other reason. It will help you remember which search terms worked successfully in which databases

b. Write the citations or record the information needed to cite each article/document you plan to read and use, or make sure that any saved a copy of the article includes all the information needed to cite it. Some article pdf files may not include all of the information needed to cite, and it's a waste of your valuable time to have to go back to search and find the items again in order to be able to cite them. Using citation management software such as EndNote will help keep track of citations and help create bibliographies for your research papers.

c. Write a summary of each article you read and/or why you want to use it.

5. Synthesize.

V. Synthesize.

A. Organize and integrate information from multiple sources

B. Present the information (create report, speech, etc. that communicates)

C. Cite material using the style required by your professor or by the venue (conference, publication, etc.). For help with citation styles, see  Guide to Citing Sources .  A link to the citing guide is also available in the "Get Help" section on the left side of the Library home page

6. Evaluate your work.

VI. Evaluate the paper, speech, or whatever you are using to communicate your research.

A. Is it effective?

B. Does it meet the requirements?

C. Ask another student or colleague to provide constructive criticism of your paper/project.

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Research Process Guide

• Step 1 - Identifying and Developing a Topic
• Step 2 - Narrowing Your Topic
• Step 3 - Developing Research Questions
• Step 4 - Conducting a Literature Review
• Step 5 - Choosing a Conceptual or Theoretical Framework
• Step 6 - Determining Research Methodology
• Step 6a - Determining Research Methodology - Quantitative Research Methods
• Step 6b - Determining Research Methodology - Qualitative Design
• Step 7 - Considering Ethical Issues in Research with Human Subjects - Institutional Review Board (IRB)
• Step 8 - Collecting Data
• Step 9 - Analyzing Data
• Step 10 - Interpreting Results
• Step 11 - Writing Up Results

Step 4: Conducting a Literature Review

In order to understand your topic, before you conduct your research, it is extremely important to immerse yourself in the research that has been done on your topic and the topics that might be adjacent to your particular research interest or questions. “a researcher cannot perform significant research without first understanding the literature in the field” (Boote & Beile, 2005, p. 3). Essentially, When writing a thesis or research proposal, the review of the literature would be your Chapter 2 .

Frankly, the literature review is often the first major challenge of the writing process. Sometimes, the task to review and synthesize all of the previous research on and around your topic can feel overwhelming. Although the literature review is foundational to situate your research within the body of literature on your topic, there is almost no literature on the challenges and pitfalls of writing a literature review (Randolph, 2009).

Boote and Beile (2005) reveal through their research on dissertation writing, that although a sophisticated literature review is essential for substantial research, they are often poorly written and lack organizational structure and conceptual relevance. So, the question is, how can you write a literature that is well-organized, comprehensive and situate your research within the literature?

Onweugbuzie et al. (2012) identify 23 core components of an effective literature review in their research and are referred to as the standard checklist for most empirical researchers. The list includes the following:

• What has been researched and what needs to be in the future.
• Identify variables within the literature that are relevant to your study.
• Identify the relationship between theory and practice within the literature.
• Discuss the quality of research with particular emphasis on the exemplary studies.
• Examine the methodologies and research design used throughout the literature, and evaluate the efficacy.
• Pay attention to any contradictions within the literature and
• Make sure to not replicate studies that have already been completed, however, if there are similarities, identify how your study and variables examined are important, different, and relevant.

How to complete a literature review

Fair Warning: The literature review is often time-consuming and can feel like an endless process.  Don’t Give Up! It is the first major hurdle of the research proposal process. Once you have completed the literature review, you will have a good idea of what is significant, relevant and novel about your research. The key is to spend time reading, recording important findings, and organizing the scholarly literature on (and around) your topic.

At this point, it is important to distinguish between scholarly literature and other sources. You need to keep in mind that you are only reviewing scholarly literature, which includes sources and studies that have a clear methodology, empirical evidence, results and conclusions. These studies are PEER-REVIEWED, meaning, contemporaries in the field have reviewed the research methods and findings of the literature, and found them relevant, significant, authentic and valid (Wakefield, 2015).

Where do you begin? Great question.

According to Randolph (2009), the goal of a literature review is to integrate and generalize findings across studies, debate findings within a field, resolve the debate, and discuss the language specific to the field. For a meta-analysis, which is a common strategy for a literature review, the goal is largely to integrate quantitative findings across the research on the topic. For other strategies to complete the literature review, the goals may be to critically analyze previous studies, identify central themes or issues within the existing literature or analyze an argument in the field (Randolph, 2009). In literature reviews for dissertation, the goal is to largely interrogate and analyze the current findings to find weaknesses or contradictions in order to place your study within the context of the current literature and to justify your study’s relevance.  So in essence, the goals of literature review, regardless of the strategy, are not only to deal with the central theme across the literature and to present a thematic analysis of that literature, but also, and perhaps more importantly, it is to focus on whether the body of knowledge is credible, reliable and valid based on the methodological approaches and outcomes of the literature in the field (Wakefield, 2015).

A few initial steps are:

• Develop a list of key words and phrases that relate to your topic and questions (Denney & Tewksbury, 2013).
• Search for relevant sources using useful databases found in Kean University’s Library :
• Kean University’s WorldCat Discovery single-search application
• ERIC (education)
• JSTOR (multidisciplinary)
• Project Muse (humanities and social science)
• Web of Science (citation searching)
• Google Scholar
• Set up an account with a bibliographic citation manager like EndNote Online (access provided by Kean University) or a freely available option such as Zotero. The EndNote Online Guide provides separate on-campus and off-campus account registration instructions. A bibliographic citation manager will not only help you manage and organize your sources, but it will also help you format your references in various citation styles.
• Take advantage of research support options provided by Kean’s librarians, including workshops , appointments with a librarian , and 24/7 Chat .

If you identify a source (article or book) that is not available through Kean University’s library collections, you may submit an Interlibrary Loan request. Book or article records found in the WorldCat Discovery database will feature an Interlibrary Loan request option. However, you may also utilize the Interlibrary Loan form .

You may also use the VALE Reciprocal Borrowing Program , which enables Kean University students and faculty to check out books from libraries at other New Jersey colleges and universities. To participate in this program, a researcher must first obtain a signed "VALE Reciprocal Borrowing Application Form" from the Nancy Thompson Learning Commons before they can borrow at one of the participating libraries .

What are the sources that are appropriate for a literature review? According to Garrard (2009) and others scientific or empirical research refers to the:

         …theoretical and research publications in scientific journals, reference books, government practice, policy statements, and other materials          about the theory, practice, and results of scientific inquiry. These materials and publications are produced by individuals or groups in          universities, foundations, government research laboratories, and other nonprofit or for-profit organizations (p.4). Onwuegbuzie et al. (2010; as cited in Onwuegbuzie et al., 2012) goes further and describes the literature that could be included in a literature review, “research articles,… essays, article reviews, monographs, dissertations, books, Internet websites, video, interview transcripts, encyclopedias, company reports, trade catalogues, government documents, congressional/parliamentary bills…” (p. 7). However, Onwuegbuzie et al. (2012) builds on this definition, by saying that a literature review is largely, “a systematic, explicit, and reproducible method for identifying, evaluating, and synthesizing the existing body of completed and recorded work produced by researchers, scholars and practitioners” (p.3).

So, what does this mean for you, the researcher and author of the literature review? You want to use multiple source types. Additionally, stick to the parameters laid out by Onwuegbuzie et al. (2012)  in that the literature reviewed should be an evaluation and synthesis of the existing work completed by “researchers, scholars and practitioners.” The list of sources should be semi-exhaustive and representative of the field.

Next, you should:

     3. Evaluate and select your sources. Read the abstract first to see if the source is relevant to your topic (Wakefield, 2015; Denney & Tewksbury, 2013; Randolph, 2009).

• Is this source peer-reviewed?
• Is this source presenting empirical evidence, meeting the threshold for scholarly research?
• Is this topic relevant to my research topic/questions?

Organizing your Literature Review:

Outline your literature review- how do you want it organized? You are “synthesizing” the literature as your purpose here. What structure works best for your topic and study? The most common formats are (Randolph, 2009; Onwuegbuzie et al., 2012):

• Historical format - literature is reviewed chronologically.This method is preferred when there is a goal of analyzing the progression of research methods, theories or practices over time.
• Conceptual format - centered arounds the propositions in research rationale or a theoretical- centered review which is organized according to the theories in the literature.
• Methodological format - this involves the discussion of methodology  as in an imperial paper including an introduction, method, results and discussion. This approach is most commonly used in meta- analytical reports.

Let’s talk about synthesis.

A literature review is not only a review of the empirical research, but it is also evaluation and synthesis of the research. Boote and Beile (2005) have created a five- category list for evaluating a literature review. The categories are coverage, synthesis, methodology, significance, and rhetoric .

• You need to create a justified criteria for including and excluding studies from your review
• You need to discuss what has been done in the field and what still needs to be done.
• Place the topic or problem within the greater context of scholarly literature.
• Place the topic or problem within the historical context.
• Discuss the subject vocabulary.
• Articulate the important variables and phenomena that are relevant to the topic.
• Synthesize and discuss a new perspective on the literature.
• Identify the main methods and research techniques that have been used in the field as well as their advantages/disadvantages.
• Relate ideas and theories to research methodologies.
• Rationalize the practical significance of the research problem.
• Rationalize the scholarly significance of the research problem.
• Write in coherent language and be sure the organization/ structure of the review makes sense.

Synthesis is difficult - you need to articulate what this literature means for your research and/or how does the literature inform the purpose, impact, methodology of your study? Rather than summarizing, the idea behind synthesis is taking the information you have discussed and drawing your own conclusions, making connections between the literature and your study.

Boote, D. N., & Beile, P. (2005). Scholars before researchers: On the centrality of the dissertation literature review in research preparation. Educational Researcher, 34 (6), 3-15. https://www.jstor.org/stable/3699805

Denney, A. S., & Tewksbury, R. (2013). How to write a literature review. Journal of Criminal Justice Education, 24 (2), 218-234. https://doi-org.kean.idm.oclc.org/10.1080/10511253.2012.730617

Garrard, J. (2009). Health sciences literature review made easy: The matrix method.  Jones and Bartlett.

Onwuegbuzie, A. J., Leech, N. L., & Collins, K. M. (2012). Qualitative analysis techniques for the review of the literature. Qualitative Report, 17( 28), 1-28.

Randolph, J. (2009). A guide to writing the dissertation literature review. Practical Assessment, Research, and Evaluation, 14 (1), 13.

Wakefield, A. (2015). Synthesising the literature as part of a literature review. Nursing Standard, 29 (29), 44-51. https://doi.org/10.7748/ns.29.29.44.e8957

• Last Updated: Jun 29, 2023 1:35 PM
• URL: https://libguides.kean.edu/ResearchProcessGuide

Research Methods: Literature Reviews

• Annotated Bibliographies
• Literature Reviews
• Scoping Reviews
• Systematic Reviews
• Scholarship of Teaching and Learning
• Persuasive Arguments
• Subject Specific Methodology

A literature review involves researching, reading, analyzing, evaluating, and summarizing scholarly literature (typically journals and articles) about a specific topic. The results of a literature review may be an entire report or article OR may be part of a article, thesis, dissertation, or grant proposal. A literature review helps the author learn about the history and nature of their topic, and identify research gaps and problems.

Steps & Elements

Problem formulation

• Determine your topic and its components by asking a question
• Research: locate literature related to your topic to identify the gap(s) that can be addressed
• Read: read the articles or other sources of information
• Analyze: assess the findings for relevancy
• Evaluating: determine how the article are relevant to your research and what are the key findings
• Synthesis: write about the key findings and how it is relevant to your research

Elements of a Literature Review

• Summarize subject, issue or theory under consideration, along with objectives of the review
• Divide works under review into categories (e.g. those in support of a particular position, those against, those offering alternative theories entirely)
• Explain how each work is similar to and how it varies from the others
• Conclude which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of an area of research

Writing a Literature Review Resources

• How to Write a Literature Review From the Wesleyan University Library
• Write a Literature Review From the University of California Santa Cruz Library. A Brief overview of a literature review, includes a list of stages for writing a lit review.
• Literature Reviews From the University of North Carolina Writing Center. Detailed information about writing a literature review.
• Undertaking a literature review: a step-by-step approach Cronin, P., Ryan, F., & Coughan, M. (2008). Undertaking a literature review: A step-by-step approach. British Journal of Nursing, 17(1), p.38-43

Literature Review Tutorial

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Soc 001: introductory sociology.

• Literature Reviews: Strategies for Writing
• Fake News and Evaluating Sources

Literature Reviews

What is a Literature Review? The literature review is a critical look at the existing research that is significant to the work that you are carrying out. This overview identifies prominent research trends in addition to assessing the overall strengths and weaknesses of the existing research.

Purpose of the Literature Review

• To provide background information about a research topic.
• To establish the importance of a topic.
• To demonstrate familiarity with a topic/problem.
• To “carve out a space” for further work and allow you to position yourself in a scholarly conversation.

Characteristics of an effective literature review In addition to fulfilling the purposes outlined above, an effective literature review provides a critical overview of existing research by

• Outlining important research trends.
• Assessing strengths and weaknesses (of individual studies as well the existing research as a whole).
• Identifying potential gaps in knowledge.
• Establishing a need for current and/or future research projects.

Steps of the Literature Review Process

1) Planning: identify the focus, type, scope and discipline of the review you intend to write. 2) Reading and Research: collect and read current research on your topic. Select only those sources that are most relevant to your project. 3) Analyzing: summarize, synthesize, critique, and compare your sources in order to assess the field of research as a whole. 4) Drafting: develop a thesis or claim to make about the existing research and decide how to organize your material. 5) Revising: revise and finalize the structural, stylistic, and grammatical issues of your paper.

This process is not always a linear process; depending on the size and scope of your literature review, you may find yourself returning to some of these steps repeatedly as you continue to focus your project.

These steps adapted from the full workshop offered by the Graduate Writing Center at Penn State. 

Literature Review Format

 Introduction

• Provide an overview of the topic, theme, or issue.
• Identify your specific area of focus.
• Describe your methodology and rationale. How did you decide which sources to include and which to exclude? Why? How is your review organized?
• Briefly discuss the overall trends in the published scholarship in this area.
•  Establish your reason for writing the review.
•  Find the best organizational method for your review.
•  Summarize sources by providing the most relevant information.
•  Respectfully and objectively critique and evaluate the studies.
•  Use direct quotations sparingly and only if appropriate.

 Conclusion

•  Summarize the major findings of the sources that you reviewed, remembering to keep the focus on your topic.
•  Evaluate the current state of scholarship in this area (ex. flaws or gaps in the research, inconsistencies in findings) 
•  Identify any areas for further research.
•  Conclude by making a connection between your topic and some larger area of study such as the discipline. 
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Passas, I. Bibliometric Analysis: The Main Steps. Encyclopedia 2024 , 4 , 1014-1025. https://doi.org/10.3390/encyclopedia4020065

Passas I. Bibliometric Analysis: The Main Steps. Encyclopedia . 2024; 4(2):1014-1025. https://doi.org/10.3390/encyclopedia4020065

Passas, Ioannis. 2024. "Bibliometric Analysis: The Main Steps" Encyclopedia 4, no. 2: 1014-1025. https://doi.org/10.3390/encyclopedia4020065

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Peer-reviewed

Research Article

Functional connectivity changes in the brain of adolescents with internet addiction: A systematic literature review of imaging studies

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Software, Validation, Visualization, Writing – original draft, Writing – review & editing

Affiliation Child and Adolescent Mental Health, Department of Brain Sciences, Great Ormond Street Institute of Child Health, University College London, London, United Kingdom

Roles Conceptualization, Supervision, Validation, Writing – review & editing

* E-mail: [email protected]

Affiliation Behavioural Brain Sciences Unit, Population Policy Practice Programme, Great Ormond Street Institute of Child Health, University College London, London, United Kingdom

• Max L. Y. Chang, 
• Irene O. Lee

• Published: June 4, 2024
• https://doi.org/10.1371/journal.pmen.0000022
• Peer Review
• Reader Comments

Internet usage has seen a stark global rise over the last few decades, particularly among adolescents and young people, who have also been diagnosed increasingly with internet addiction (IA). IA impacts several neural networks that influence an adolescent’s behaviour and development. This article issued a literature review on the resting-state and task-based functional magnetic resonance imaging (fMRI) studies to inspect the consequences of IA on the functional connectivity (FC) in the adolescent brain and its subsequent effects on their behaviour and development. A systematic search was conducted from two databases, PubMed and PsycINFO, to select eligible articles according to the inclusion and exclusion criteria. Eligibility criteria was especially stringent regarding the adolescent age range (10–19) and formal diagnosis of IA. Bias and quality of individual studies were evaluated. The fMRI results from 12 articles demonstrated that the effects of IA were seen throughout multiple neural networks: a mix of increases/decreases in FC in the default mode network; an overall decrease in FC in the executive control network; and no clear increase or decrease in FC within the salience network and reward pathway. The FC changes led to addictive behaviour and tendencies in adolescents. The subsequent behavioural changes are associated with the mechanisms relating to the areas of cognitive control, reward valuation, motor coordination, and the developing adolescent brain. Our results presented the FC alterations in numerous brain regions of adolescents with IA leading to the behavioural and developmental changes. Research on this topic had a low frequency with adolescent samples and were primarily produced in Asian countries. Future research studies of comparing results from Western adolescent samples provide more insight on therapeutic intervention.

Citation: Chang MLY, Lee IO (2024) Functional connectivity changes in the brain of adolescents with internet addiction: A systematic literature review of imaging studies. PLOS Ment Health 1(1): e0000022. https://doi.org/10.1371/journal.pmen.0000022

Editor: Kizito Omona, Uganda Martyrs University, UGANDA

Received: December 29, 2023; Accepted: March 18, 2024; Published: June 4, 2024

Copyright: © 2024 Chang, Lee. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting information files.

Funding: The authors received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Introduction

The behavioural addiction brought on by excessive internet use has become a rising source of concern [ 1 ] since the last decade. According to clinical studies, individuals with Internet Addiction (IA) or Internet Gaming Disorder (IGD) may have a range of biopsychosocial effects and is classified as an impulse-control disorder owing to its resemblance to pathological gambling and substance addiction [ 2 , 3 ]. IA has been defined by researchers as a person’s inability to resist the urge to use the internet, which has negative effects on their psychological well-being as well as their social, academic, and professional lives [ 4 ]. The symptoms can have serious physical and interpersonal repercussions and are linked to mood modification, salience, tolerance, impulsivity, and conflict [ 5 ]. In severe circumstances, people may experience severe pain in their bodies or health issues like carpal tunnel syndrome, dry eyes, irregular eating and disrupted sleep [ 6 ]. Additionally, IA is significantly linked to comorbidities with other psychiatric disorders [ 7 ].

Stevens et al (2021) reviewed 53 studies including 17 countries and reported the global prevalence of IA was 3.05% [ 8 ]. Asian countries had a higher prevalence (5.1%) than European countries (2.7%) [ 8 ]. Strikingly, adolescents and young adults had a global IGD prevalence rate of 9.9% which matches previous literature that reported historically higher prevalence among adolescent populations compared to adults [ 8 , 9 ]. Over 80% of adolescent population in the UK, the USA, and Asia have direct access to the internet [ 10 ]. Children and adolescents frequently spend more time on media (possibly 7 hours and 22 minutes per day) than at school or sleeping [ 11 ]. Developing nations have also shown a sharp rise in teenage internet usage despite having lower internet penetration rates [ 10 ]. Concerns regarding the possible harms that overt internet use could do to adolescents and their development have arisen because of this surge, especially the significant impacts by the COVID-19 pandemic [ 12 ]. The growing prevalence and neurocognitive consequences of IA among adolescents makes this population a vital area of study [ 13 ].

Adolescence is a crucial developmental stage during which people go through significant changes in their biology, cognition, and personalities [ 14 ]. Adolescents’ emotional-behavioural functioning is hyperactivated, which creates risk of psychopathological vulnerability [ 15 ]. In accordance with clinical study results [ 16 ], this emotional hyperactivity is supported by a high level of neuronal plasticity. This plasticity enables teenagers to adapt to the numerous physical and emotional changes that occur during puberty as well as develop communication techniques and gain independence [ 16 ]. However, the strong neuronal plasticity is also associated with risk-taking and sensation seeking [ 17 ] which may lead to IA.

Despite the fact that the precise neuronal mechanisms underlying IA are still largely unclear, functional magnetic resonance imaging (fMRI) method has been used by scientists as an important framework to examine the neuropathological changes occurring in IA, particularly in the form of functional connectivity (FC) [ 18 ]. fMRI research study has shown that IA alters both the functional and structural makeup of the brain [ 3 ].

We hypothesise that IA has widespread neurological alteration effects rather than being limited to a few specific brain regions. Further hypothesis holds that according to these alterations of FC between the brain regions or certain neural networks, adolescents with IA would experience behavioural changes. An investigation of these domains could be useful for creating better procedures and standards as well as minimising the negative effects of overt internet use. This literature review aims to summarise and analyse the evidence of various imaging studies that have investigated the effects of IA on the FC in adolescents. This will be addressed through two research questions:

• How does internet addiction affect the functional connectivity in the adolescent brain?
• How is adolescent behaviour and development impacted by functional connectivity changes due to internet addiction?

The review protocol was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (see S1 Checklist ).

Search strategy and selection process

A systematic search was conducted up until April 2023 from two sources of database, PubMed and PsycINFO, using a range of terms relevant to the title and research questions (see full list of search terms in S1 Appendix ). All the searched articles can be accessed in the S1 Data . The eligible articles were selected according to the inclusion and exclusion criteria. Inclusion criteria used for the present review were: (i) participants in the studies with clinical diagnosis of IA; (ii) participants between the ages of 10 and 19; (iii) imaging research investigations; (iv) works published between January 2013 and April 2023; (v) written in English language; (vi) peer-reviewed papers and (vii) full text. The numbers of articles excluded due to not meeting the inclusion criteria are shown in Fig 1 . Each study’s title and abstract were screened for eligibility.

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

https://doi.org/10.1371/journal.pmen.0000022.g001

Quality appraisal

Full texts of all potentially relevant studies were then retrieved and further appraised for eligibility. Furthermore, articles were critically appraised based on the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) framework to evaluate the individual study for both quality and bias. The subsequent quality levels were then appraised to each article and listed as either low, moderate, or high.

Data collection process

Data that satisfied the inclusion requirements was entered into an excel sheet for data extraction and further selection. An article’s author, publication year, country, age range, participant sample size, sex, area of interest, measures, outcome and article quality were all included in the data extraction spreadsheet. Studies looking at FC, for instance, were grouped, while studies looking at FC in specific area were further divided into sub-groups.

Data synthesis and analysis

Articles were classified according to their location in the brain as well as the network or pathway they were a part of to create a coherent narrative between the selected studies. Conclusions concerning various research trends relevant to particular groupings were drawn from these groupings and subgroupings. To maintain the offered information in a prominent manner, these assertions were entered into the data extraction excel spreadsheet.

With the search performed on the selected databases, 238 articles in total were identified (see Fig 1 ). 15 duplicated articles were eliminated, and another 6 items were removed for various other reasons. Title and abstract screening eliminated 184 articles because they were not in English (number of article, n, = 7), did not include imaging components (n = 47), had adult participants (n = 53), did not have a clinical diagnosis of IA (n = 19), did not address FC in the brain (n = 20), and were published outside the desired timeframe (n = 38). A further 21 papers were eliminated for failing to meet inclusion requirements after the remaining 33 articles underwent full-text eligibility screening. A total of 12 papers were deemed eligible for this review analysis.

Characteristics of the included studies, as depicted in the data extraction sheet in Table 1 provide information of the author(s), publication year, sample size, study location, age range, gender, area of interest, outcome, measures used and quality appraisal. Most of the studies in this review utilised resting state functional magnetic resonance imaging techniques (n = 7), with several studies demonstrating task-based fMRI procedures (n = 3), and the remaining studies utilising whole-brain imaging measures (n = 2). The studies were all conducted in Asiatic countries, specifically coming from China (8), Korea (3), and Indonesia (1). Sample sizes ranged from 12 to 31 participants with most of the imaging studies having comparable sample sizes. Majority of the studies included a mix of male and female participants (n = 8) with several studies having a male only participant pool (n = 3). All except one of the mixed gender studies had a majority male participant pool. One study did not disclose their data on the gender demographics of their experiment. Study years ranged from 2013–2022, with 2 studies in 2013, 3 studies in 2014, 3 studies in 2015, 1 study in 2017, 1 study in 2020, 1 study in 2021, and 1 study in 2022.

https://doi.org/10.1371/journal.pmen.0000022.t001

(1) How does internet addiction affect the functional connectivity in the adolescent brain?

The included studies were organised according to the brain region or network that they were observing. The specific networks affected by IA were the default mode network, executive control system, salience network and reward pathway. These networks are vital components of adolescent behaviour and development [ 31 ]. The studies in each section were then grouped into subsections according to their specific brain regions within their network.

Default mode network (DMN)/reward network.

Out of the 12 studies, 3 have specifically studied the default mode network (DMN), and 3 observed whole-brain FC that partially included components of the DMN. The effect of IA on the various centres of the DMN was not unilaterally the same. The findings illustrate a complex mix of increases and decreases in FC depending on the specific region in the DMN (see Table 2 and Fig 2 ). The alteration of FC in posterior cingulate cortex (PCC) in the DMN was the most frequently reported area in adolescents with IA, which involved in attentional processes [ 32 ], but Lee et al. (2020) additionally found alterations of FC in other brain regions, such as anterior insula cortex, a node in the DMN that controls the integration of motivational and cognitive processes [ 20 ].

https://doi.org/10.1371/journal.pmen.0000022.g002

The overall changes of functional connectivity in the brain network including default mode network (DMN), executive control network (ECN), salience network (SN) and reward network. IA = Internet Addiction, FC = Functional Connectivity.

https://doi.org/10.1371/journal.pmen.0000022.t002

Ding et al. (2013) revealed altered FC in the cerebellum, the middle temporal gyrus, and the medial prefrontal cortex (mPFC) [ 22 ]. They found that the bilateral inferior parietal lobule, left superior parietal lobule, and right inferior temporal gyrus had decreased FC, while the bilateral posterior lobe of the cerebellum and the medial temporal gyrus had increased FC [ 22 ]. The right middle temporal gyrus was found to have 111 cluster voxels (t = 3.52, p<0.05) and the right inferior parietal lobule was found to have 324 cluster voxels (t = -4.07, p<0.05) with an extent threshold of 54 voxels (figures above this threshold are deemed significant) [ 22 ]. Additionally, there was a negative correlation, with 95 cluster voxels (p<0.05) between the FC of the left superior parietal lobule and the PCC with the Chen Internet Addiction Scores (CIAS) which are used to determine the severity of IA [ 22 ]. On the other hand, in regions of the reward system, connection with the PCC was positively connected with CIAS scores [ 22 ]. The most significant was the right praecuneus with 219 cluster voxels (p<0.05) [ 22 ]. Wang et al. (2017) also discovered that adolescents with IA had 33% less FC in the left inferior parietal lobule and 20% less FC in the dorsal mPFC [ 24 ]. A potential connection between the effects of substance use and overt internet use is revealed by the generally decreased FC in these areas of the DMN of teenagers with drug addiction and IA [ 35 ].

The putamen was one of the main regions of reduced FC in adolescents with IA [ 19 ]. The putamen and the insula-operculum demonstrated significant group differences regarding functional connectivity with a cluster size of 251 and an extent threshold of 250 (Z = 3.40, p<0.05) [ 19 ]. The molecular mechanisms behind addiction disorders have been intimately connected to decreased striatal dopaminergic function [ 19 ], making this function crucial.

Executive Control Network (ECN).

5 studies out of 12 have specifically viewed parts of the executive control network (ECN) and 3 studies observed whole-brain FC. The effects of IA on the ECN’s constituent parts were consistent across all the studies examined for this analysis (see Table 2 and Fig 3 ). The results showed a notable decline in all the ECN’s major centres. Li et al. (2014) used fMRI imaging and a behavioural task to study response inhibition in adolescents with IA [ 25 ] and found decreased activation at the striatum and frontal gyrus, particularly a reduction in FC at inferior frontal gyrus, in the IA group compared to controls [ 25 ]. The inferior frontal gyrus showed a reduction in FC in comparison to the controls with a cluster size of 71 (t = 4.18, p<0.05) [ 25 ]. In addition, the frontal-basal ganglia pathways in the adolescents with IA showed little effective connection between areas and increased degrees of response inhibition [ 25 ].

https://doi.org/10.1371/journal.pmen.0000022.g003

Lin et al. (2015) found that adolescents with IA demonstrated disrupted corticostriatal FC compared to controls [ 33 ]. The corticostriatal circuitry experienced decreased connectivity with the caudate, bilateral anterior cingulate cortex (ACC), as well as the striatum and frontal gyrus [ 33 ]. The inferior ventral striatum showed significantly reduced FC with the subcallosal ACC and caudate head with cluster size of 101 (t = -4.64, p<0.05) [ 33 ]. Decreased FC in the caudate implies dysfunction of the corticostriatal-limbic circuitry involved in cognitive and emotional control [ 36 ]. The decrease in FC in both the striatum and frontal gyrus is related to inhibitory control, a common deficit seen with disruptions with the ECN [ 33 ].

The dorsolateral prefrontal cortex (DLPFC), ACC, and right supplementary motor area (SMA) of the prefrontal cortex were all found to have significantly decreased grey matter volume [ 29 ]. In addition, the DLPFC, insula, temporal cortices, as well as significant subcortical regions like the striatum and thalamus, showed decreased FC [ 29 ]. According to Tremblay (2009), the striatum plays a significant role in the processing of rewards, decision-making, and motivation [ 37 ]. Chen et al. (2020) reported that the IA group demonstrated increased impulsivity as well as decreased reaction inhibition using a Stroop colour-word task [ 26 ]. Furthermore, Chen et al. (2020) observed that the left DLPFC and dorsal striatum experienced a negative connection efficiency value, specifically demonstrating that the dorsal striatum activity suppressed the left DLPFC [ 27 ].

Salience network (SN).

Out of the 12 chosen studies, 3 studies specifically looked at the salience network (SN) and 3 studies have observed whole-brain FC. Relative to the DMN and ECN, the findings on the SN were slightly sparser. Despite this, adolescents with IA demonstrated a moderate decrease in FC, as well as other measures like fibre connectivity and cognitive control, when compared to healthy control (see Table 2 and Fig 4 ).

https://doi.org/10.1371/journal.pmen.0000022.g004

Xing et al. (2014) used both dorsal anterior cingulate cortex (dACC) and insula to test FC changes in the SN of adolescents with IA and found decreased structural connectivity in the SN as well as decreased fractional anisotropy (FA) that correlated to behaviour performance in the Stroop colour word-task [ 21 ]. They examined the dACC and insula to determine whether the SN’s disrupted connectivity may be linked to the SN’s disruption of regulation, which would explain the impaired cognitive control seen in adolescents with IA. However, researchers did not find significant FC differences in the SN when compared to the controls [ 21 ]. These results provided evidence for the structural changes in the interconnectivity within SN in adolescents with IA.

Wang et al. (2017) investigated network interactions between the DMN, ECN, SN and reward pathway in IA subjects [ 24 ] (see Fig 5 ), and found 40% reduction of FC between the DMN and specific regions of the SN, such as the insula, in comparison to the controls (p = 0.008) [ 24 ]. The anterior insula and dACC are two areas that are impacted by this altered FC [ 24 ]. This finding supports the idea that IA has similar neurobiological abnormalities with other addictive illnesses, which is in line with a study that discovered disruptive changes in the SN and DMN’s interaction in cocaine addiction [ 38 ]. The insula has also been linked to the intensity of symptoms and has been implicated in the development of IA [ 39 ].

“+” indicates an increase in behaivour; “-”indicates a decrease in behaviour; solid arrows indicate a direct network interaction; and the dotted arrows indicates a reduction in network interaction. This diagram depicts network interactions juxtaposed with engaging in internet related behaviours. Through the neural interactions, the diagram illustrates how the networks inhibit or amplify internet usage and vice versa. Furthermore, it demonstrates how the SN mediates both the DMN and ECN.

https://doi.org/10.1371/journal.pmen.0000022.g005

(2) How is adolescent behaviour and development impacted by functional connectivity changes due to internet addiction?

The findings that IA individuals demonstrate an overall decrease in FC in the DMN is supported by numerous research [ 24 ]. Drug addict populations also exhibited similar decline in FC in the DMN [ 40 ]. The disruption of attentional orientation and self-referential processing for both substance and behavioural addiction was then hypothesised to be caused by DMN anomalies in FC [ 41 ].

In adolescents with IA, decline of FC in the parietal lobule affects visuospatial task-related behaviour [ 22 ], short-term memory [ 42 ], and the ability of controlling attention or restraining motor responses during response inhibition tests [ 42 ]. Cue-induced gaming cravings are influenced by the DMN [ 43 ]. A visual processing area called the praecuneus links gaming cues to internal information [ 22 ]. A meta-analysis found that the posterior cingulate cortex activity of individuals with IA during cue-reactivity tasks was connected with their gaming time [ 44 ], suggesting that excessive gaming may impair DMN function and that individuals with IA exert more cognitive effort to control it. Findings for the behavioural consequences of FC changes in the DMN illustrate its underlying role in regulating impulsivity, self-monitoring, and cognitive control.

Furthermore, Ding et al. (2013) reported an activation of components of the reward pathway, including areas like the nucleus accumbens, praecuneus, SMA, caudate, and thalamus, in connection to the DMN [ 22 ]. The increased FC of the limbic and reward networks have been confirmed to be a major biomarker for IA [ 45 , 46 ]. The increased reinforcement in these networks increases the strength of reward stimuli and makes it more difficult for other networks, namely the ECN, to down-regulate the increased attention [ 29 ] (See Fig 5 ).

Executive control network (ECN).

The numerous IA-affected components in the ECN have a role in a variety of behaviours that are connected to both response inhibition and emotional regulation [ 47 ]. For instance, brain regions like the striatum, which are linked to impulsivity and the reward system, are heavily involved in the act of playing online games [ 47 ]. Online game play activates the striatum, which suppresses the left DLPFC in ECN [ 48 ]. As a result, people with IA may find it difficult to control their want to play online games [ 48 ]. This system thus causes impulsive and protracted gaming conduct, lack of inhibitory control leading to the continued use of internet in an overt manner despite a variety of negative effects, personal distress, and signs of psychological dependence [ 33 ] (See Fig 5 ).

Wang et al. (2017) report that disruptions in cognitive control networks within the ECN are frequently linked to characteristics of substance addiction [ 24 ]. With samples that were addicted to heroin and cocaine, previous studies discovered abnormal FC in the ECN and the PFC [ 49 ]. Electronic gaming is known to promote striatal dopamine release, similar to drug addiction [ 50 ]. According to Drgonova and Walther (2016), it is hypothesised that dopamine could stimulate the reward system of the striatum in the brain, leading to a loss of impulse control and a failure of prefrontal lobe executive inhibitory control [ 51 ]. In the end, IA’s resemblance to drug use disorders may point to vital biomarkers or underlying mechanisms that explain how cognitive control and impulsive behaviour are related.

A task-related fMRI study found that the decrease in FC between the left DLPFC and dorsal striatum was congruent with an increase in impulsivity in adolescents with IA [ 26 ]. The lack of response inhibition from the ECN results in a loss of control over internet usage and a reduced capacity to display goal-directed behaviour [ 33 ]. Previous studies have linked the alteration of the ECN in IA with higher cue reactivity and impaired ability to self-regulate internet specific stimuli [ 52 ].

Salience network (SN)/ other networks.

Xing et al. (2014) investigated the significance of the SN regarding cognitive control in teenagers with IA [ 21 ]. The SN, which is composed of the ACC and insula, has been demonstrated to control dynamic changes in other networks to modify cognitive performance [ 21 ]. The ACC is engaged in conflict monitoring and cognitive control, according to previous neuroimaging research [ 53 ]. The insula is a region that integrates interoceptive states into conscious feelings [ 54 ]. The results from Xing et al. (2014) showed declines in the SN regarding its structural connectivity and fractional anisotropy, even though they did not observe any appreciable change in FC in the IA participants [ 21 ]. Due to the small sample size, the results may have indicated that FC methods are not sensitive enough to detect the significant functional changes [ 21 ]. However, task performance behaviours associated with impaired cognitive control in adolescents with IA were correlated with these findings [ 21 ]. Our comprehension of the SN’s broader function in IA can be enhanced by this relationship.

Research study supports the idea that different psychological issues are caused by the functional reorganisation of expansive brain networks, such that strong association between SN and DMN may provide neurological underpinnings at the system level for the uncontrollable character of internet-using behaviours [ 24 ]. In the study by Wang et al. (2017), the decreased interconnectivity between the SN and DMN, comprising regions such the DLPFC and the insula, suggests that adolescents with IA may struggle to effectively inhibit DMN activity during internally focused processing, leading to poorly managed desires or preoccupations to use the internet [ 24 ] (See Fig 5 ). Subsequently, this may cause a failure to inhibit DMN activity as well as a restriction of ECN functionality [ 55 ]. As a result, the adolescent experiences an increased salience and sensitivity towards internet addicting cues making it difficult to avoid these triggers [ 56 ].

The primary aim of this review was to present a summary of how internet addiction impacts on the functional connectivity of adolescent brain. Subsequently, the influence of IA on the adolescent brain was compartmentalised into three sections: alterations of FC at various brain regions, specific FC relationships, and behavioural/developmental changes. Overall, the specific effects of IA on the adolescent brain were not completely clear, given the variety of FC changes. However, there were overarching behavioural, network and developmental trends that were supported that provided insight on adolescent development.

The first hypothesis that was held about this question was that IA was widespread and would be regionally similar to substance-use and gambling addiction. After conducting a review of the information in the chosen articles, the hypothesis was predictably supported. The regions of the brain affected by IA are widespread and influence multiple networks, mainly DMN, ECN, SN and reward pathway. In the DMN, there was a complex mix of increases and decreases within the network. However, in the ECN, the alterations of FC were more unilaterally decreased, but the findings of SN and reward pathway were not quite clear. Overall, the FC changes within adolescents with IA are very much network specific and lay a solid foundation from which to understand the subsequent behaviour changes that arise from the disorder.

The second hypothesis placed emphasis on the importance of between network interactions and within network interactions in the continuation of IA and the development of its behavioural symptoms. The results from the findings involving the networks, DMN, SN, ECN and reward system, support this hypothesis (see Fig 5 ). Studies confirm the influence of all these neural networks on reward valuation, impulsivity, salience to stimuli, cue reactivity and other changes that alter behaviour towards the internet use. Many of these changes are connected to the inherent nature of the adolescent brain.

There are multiple explanations that underlie the vulnerability of the adolescent brain towards IA related urges. Several of them have to do with the inherent nature and underlying mechanisms of the adolescent brain. Children’s emotional, social, and cognitive capacities grow exponentially during childhood and adolescence [ 57 ]. Early teenagers go through a process called “social reorientation” that is characterised by heightened sensitivity to social cues and peer connections [ 58 ]. Adolescents’ improvements in their social skills coincide with changes in their brains’ anatomical and functional organisation [ 59 ]. Functional hubs exhibit growing connectivity strength [ 60 ], suggesting increased functional integration during development. During this time, the brain’s functional networks change from an anatomically dominant structure to a scattered architecture [ 60 ].

The adolescent brain is very responsive to synaptic reorganisation and experience cues [ 61 ]. As a result, one of the distinguishing traits of the maturation of adolescent brains is the variation in neural network trajectory [ 62 ]. Important weaknesses of the adolescent brain that may explain the neurobiological change brought on by external stimuli are illustrated by features like the functional gaps between networks and the inadequate segregation of networks [ 62 ].

The implications of these findings towards adolescent behaviour are significant. Although the exact changes and mechanisms are not fully clear, the observed changes in functional connectivity have the capacity of influencing several aspects of adolescent development. For example, functional connectivity has been utilised to investigate attachment styles in adolescents [ 63 ]. It was observed that adolescent attachment styles were negatively associated with caudate-prefrontal connectivity, but positively with the putamen-visual area connectivity [ 63 ]. Both named areas were also influenced by the onset of internet addiction, possibly providing a connection between the two. Another study associated neighbourhood/socioeconomic disadvantage with functional connectivity alterations in the DMN and dorsal attention network [ 64 ]. The study also found multivariate brain behaviour relationships between the altered/disadvantaged functional connectivity and mental health and cognition [ 64 ]. This conclusion supports the notion that the functional connectivity alterations observed in IA are associated with specific adolescent behaviours as well as the fact that functional connectivity can be utilised as a platform onto which to compare various neurologic conditions.

Limitations/strengths

There were several limitations that were related to the conduction of the review as well as the data extracted from the articles. Firstly, the study followed a systematic literature review design when analysing the fMRI studies. The data pulled from these imaging studies were namely qualitative and were subject to bias contrasting the quantitative nature of statistical analysis. Components of the study, such as sample sizes, effect sizes, and demographics were not weighted or controlled. The second limitation brought up by a similar review was the lack of a universal consensus of terminology given IA [ 47 ]. Globally, authors writing about this topic use an array of terminology including online gaming addiction, internet addiction, internet gaming disorder, and problematic internet use. Often, authors use multiple terms interchangeably which makes it difficult to depict the subtle similarities and differences between the terms.

Reviewing the explicit limitations in each of the included studies, two major limitations were brought up in many of the articles. One was relating to the cross-sectional nature of the included studies. Due to the inherent qualities of a cross-sectional study, the studies did not provide clear evidence that IA played a causal role towards the development of the adolescent brain. While several biopsychosocial factors mediate these interactions, task-based measures that combine executive functions with imaging results reinforce the assumed connection between the two that is utilised by the papers studying IA. Another limitation regarded the small sample size of the included studies, which averaged to around 20 participants. The small sample size can influence the generalisation of the results as well as the effectiveness of statistical analyses. Ultimately, both included study specific limitations illustrate the need for future studies to clarify the causal relationship between the alterations of FC and the development of IA.

Another vital limitation was the limited number of studies applying imaging techniques for investigations on IA in adolescents were a uniformly Far East collection of studies. The reason for this was because the studies included in this review were the only fMRI studies that were found that adhered to the strict adolescent age restriction. The adolescent age range given by the WHO (10–19 years old) [ 65 ] was strictly followed. It is important to note that a multitude of studies found in the initial search utilised an older adolescent demographic that was slightly higher than the WHO age range and had a mean age that was outside of the limitations. As a result, the results of this review are biased and based on the 12 studies that met the inclusion and exclusion criteria.

Regarding the global nature of the research, although the journals that the studies were published in were all established western journals, the collection of studies were found to all originate from Asian countries, namely China and Korea. Subsequently, it pulls into question if the results and measures from these studies are generalisable towards a western population. As stated previously, Asian countries have a higher prevalence of IA, which may be the reasoning to why the majority of studies are from there [ 8 ]. However, in an additional search including other age groups, it was found that a high majority of all FC studies on IA were done in Asian countries. Interestingly, western papers studying fMRI FC were primarily focused on gambling and substance-use addiction disorders. The western papers on IA were less focused on fMRI FC but more on other components of IA such as sleep, game-genre, and other non-imaging related factors. This demonstrated an overall lack of western fMRI studies on IA. It is important to note that both western and eastern fMRI studies on IA presented an overall lack on children and adolescents in general.

Despite the several limitations, this review provided a clear reflection on the state of the data. The strengths of the review include the strict inclusion/exclusion criteria that filtered through studies and only included ones that contained a purely adolescent sample. As a result, the information presented in this review was specific to the review’s aims. Given the sparse nature of adolescent specific fMRI studies on the FC changes in IA, this review successfully provided a much-needed niche representation of adolescent specific results. Furthermore, the review provided a thorough functional explanation of the DMN, ECN, SN and reward pathway making it accessible to readers new to the topic.

Future directions and implications

Through the search process of the review, there were more imaging studies focused on older adolescence and adulthood. Furthermore, finding a review that covered a strictly adolescent population, focused on FC changes, and was specifically depicting IA, was proven difficult. Many related reviews, such as Tereshchenko and Kasparov (2019), looked at risk factors related to the biopsychosocial model, but did not tackle specific alterations in specific structural or functional changes in the brain [ 66 ]. Weinstein (2017) found similar structural and functional results as well as the role IA has in altering response inhibition and reward valuation in adolescents with IA [ 47 ]. Overall, the accumulated findings only paint an emerging pattern which aligns with similar substance-use and gambling disorders. Future studies require more specificity in depicting the interactions between neural networks, as well as more literature on adolescent and comorbid populations. One future field of interest is the incorporation of more task-based fMRI data. Advances in resting-state fMRI methods have yet to be reflected or confirmed in task-based fMRI methods [ 62 ]. Due to the fact that network connectivity is shaped by different tasks, it is critical to confirm that the findings of the resting state fMRI studies also apply to the task based ones [ 62 ]. Subsequently, work in this area will confirm if intrinsic connectivity networks function in resting state will function similarly during goal directed behaviour [ 62 ]. An elevated focus on adolescent populations as well as task-based fMRI methodology will help uncover to what extent adolescent network connectivity maturation facilitates behavioural and cognitive development [ 62 ].

A treatment implication is the potential usage of bupropion for the treatment of IA. Bupropion has been previously used to treat patients with gambling disorder and has been effective in decreasing overall gambling behaviour as well as money spent while gambling [ 67 ]. Bae et al. (2018) found a decrease in clinical symptoms of IA in line with a 12-week bupropion treatment [ 31 ]. The study found that bupropion altered the FC of both the DMN and ECN which in turn decreased impulsivity and attentional deficits for the individuals with IA [ 31 ]. Interventions like bupropion illustrate the importance of understanding the fundamental mechanisms that underlie disorders like IA.

The goal for this review was to summarise the current literature on functional connectivity changes in adolescents with internet addiction. The findings answered the primary research questions that were directed at FC alterations within several networks of the adolescent brain and how that influenced their behaviour and development. Overall, the research demonstrated several wide-ranging effects that influenced the DMN, SN, ECN, and reward centres. Additionally, the findings gave ground to important details such as the maturation of the adolescent brain, the high prevalence of Asian originated studies, and the importance of task-based studies in this field. The process of making this review allowed for a thorough understanding IA and adolescent brain interactions.

Given the influx of technology and media in the lives and education of children and adolescents, an increase in prevalence and focus on internet related behavioural changes is imperative towards future children/adolescent mental health. Events such as COVID-19 act to expose the consequences of extended internet usage on the development and lifestyle of specifically young people. While it is important for parents and older generations to be wary of these changes, it is important for them to develop a base understanding of the issue and not dismiss it as an all-bad or all-good scenario. Future research on IA will aim to better understand the causal relationship between IA and psychological symptoms that coincide with it. The current literature regarding functional connectivity changes in adolescents is limited and requires future studies to test with larger sample sizes, comorbid populations, and populations outside Far East Asia.

This review aimed to demonstrate the inner workings of how IA alters the connection between the primary behavioural networks in the adolescent brain. Predictably, the present answers merely paint an unfinished picture that does not necessarily depict internet usage as overwhelmingly positive or negative. Alternatively, the research points towards emerging patterns that can direct individuals on the consequences of certain variables or risk factors. A clearer depiction of the mechanisms of IA would allow physicians to screen and treat the onset of IA more effectively. Clinically, this could be in the form of more streamlined and accurate sessions of CBT or family therapy, targeting key symptoms of IA. Alternatively clinicians could potentially prescribe treatment such as bupropion to target FC in certain regions of the brain. Furthermore, parental education on IA is another possible avenue of prevention from a public health standpoint. Parents who are aware of the early signs and onset of IA will more effectively handle screen time, impulsivity, and minimize the risk factors surrounding IA.

Additionally, an increased attention towards internet related fMRI research is needed in the West, as mentioned previously. Despite cultural differences, Western countries may hold similarities to the eastern countries with a high prevalence of IA, like China and Korea, regarding the implications of the internet and IA. The increasing influence of the internet on the world may contribute to an overall increase in the global prevalence of IA. Nonetheless, the high saturation of eastern studies in this field should be replicated with a Western sample to determine if the same FC alterations occur. A growing interest in internet related research and education within the West will hopefully lead to the knowledge of healthier internet habits and coping strategies among parents with children and adolescents. Furthermore, IA research has the potential to become a crucial proxy for which to study adolescent brain maturation and development.

Supporting information

S1 checklist. prisma checklist..

https://doi.org/10.1371/journal.pmen.0000022.s001

S1 Appendix. Search strategies with all the terms.

https://doi.org/10.1371/journal.pmen.0000022.s002

S1 Data. Article screening records with details of categorized content.

https://doi.org/10.1371/journal.pmen.0000022.s003

Acknowledgments

The authors thank https://www.stockio.com/free-clipart/brain-01 (with attribution to Stockio.com); and https://www.rawpixel.com/image/6442258/png-sticker-vintage for the free images used to create Figs 2 – 4 .

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• Open access
• Published: 21 June 2024

The evolution of TAVI performance overtime: an overview of systematic reviews

• Carmen Angioletti 1 ,
• Giaele Moretti 1 ,
• Stefania Manetti 2 ,
• Luigi Pastormerlo 3 ,
• Milena Vainieri 1 &
• Claudio Passino 3 , 4  

BMC Cardiovascular Disorders volume  24 , Article number:  314 ( 2024 ) Cite this article

Metrics details

Transcatheter aortic valve implantation (TAVI) is a well-established treatment for high and intermediate-risk patients with severe aortic stenosis (AS). Recent studies have demonstrated non-inferiority of TAVI compared to surgery in low-risk patients. In the past decade, numerous literature reviews (SLRs) have assessed the use of TAVI in different risk groups. This is the first attempt to provide an overview of SRs (OoSRs) focusing on secondary studies reporting clinical outcomes/process indicators. This research aims to summarize the findings of extant literature on the performance of TAVI over time.

A literature search took place from inception to April 2024. We searched MEDLINE and the Cochrane Library for SLRs. SLRs reporting at least one review of clinical indicators were included. Subsequently, a two-step inclusion process was conducted: [ 1 ] screening based on title and abstracts and [ 2 ] screening based on full-text papers. Relevant data were extracted and the quality of the reviews was assessed.

We included 33 SLRs with different risks assessed via the Society of Thoracic Surgeons (STS) score. Mortality rates were comparable between TAVI and Surgical Aortic Valve Replacement (SAVR) groups. TAVI is associated with lower rates of major bleeding, acute kidney injury (AKI) incidence, and new-onset atrial fibrillation. Vascular complications, pacemaker implantation, and residual aortic regurgitation were more frequent in TAVI patients.

This study summarizes TAVI performance findings over a decade, revealing a shift to include both high and low-risk patients since 2020. Overall, TAVI continues to evolve, emphasizing improved outcomes, broader indications, and addressing challenges.

Peer Review reports

Aortic stenosis (AS) is a condition caused by the narrowing of the aortic valve and is one of the most common valvular diseases. The prevalence of severe aortic stenosis in subjects aged ≥ 75 years is about 3.4% in Western countries [ 1 ]. Resulting symptoms include shortness of breath, chest pain, fatigue, and reduced exercise tolerance. If left untreated, AS can lead to heart failure and death [ 2 ]. For decades, Surgical Aortic Valve Replacement (SAVR), which involves an open-heart surgery in which the diseased aortic valve is replaced with a prosthetic valve, has been considered the gold standard treatment [ 3 ]Transcatheter aortic valve implantation (TAVI) is a minimally invasive procedure that has progressively emerged as a valid treatment option in prohibitive, high, and intermediate-risk patients [ 4 ] respectively. More recently, randomized trials have demonstrated non-inferiority of TAVI compared to surgery in low-risk patients as assessed by the Society of Thoracic Surgeons (STS) score. TAVI is performed by percutaneous delivery of a bioprosthetic valve through a catheter typically inserted via the femoral artery. Unlike SAVR, TAVI can be performed under local anaesthesia, and conscious sedation with minimalist vascular access. Over the past decade, an increasing number of systematic reviews (SRs) have been conducted to validate the extent of the indication for TAVI in low-risk patients. This is the first effort to summarize the evidence in an overview of SRs (OoSRs) focusing exclusively on secondary studies that have reported at least one review of clinical outcomes/process indicators. The aim of this research is to summarize the findings of extant literature reviews on the performance of TAVI over time. This study provides a useful overview of the main Key Performance Indicators (KPI) such as early and late mortality, discussing the evolution of TAVI in terms of the target population and the related results over time to highlight whether and where there are uncertain findings requiring further investigation.

Data searches and study selection

The authors declare that all supporting data are available within the article. This work constitutes an umbrella approach to identifying both SLRs and RCTs.

A purposive literature search for SLRs took place from the beginning (2013) to January 2023. We searched MEDLINE (via PubMed) and the Cochrane Library for SRs. A more comprehensive search strategy was applied in MEDLINE, using the medical subject heading (Appendix I in the Data Supplement). For all included studies, reference lists were also searched.

Four independent overview authors (SM, LP, GM, and CA) screened the titles and abstracts against the eligibility criteria for inclusion.

Search strategy: (“TAVI“[Title/Abstract] OR “transcatheter aortic valve implantation“[Title/Abstract] OR “TAVR“[Title/Abstract] OR " transcatheter aortic valve replacement “[Title/Abstract] OR “transcatheter aortic valve replacement“[MeSH Terms]) AND (“Review“[Title/Abstract] OR “meta-analysis“[Title/Abstract] OR “meta-analysis as topic“[MeSH Terms])

We searched for SLRs that compared the efficacy and safety of TAVI in patients with aortic stenosis and analyzed the full texts to extract the eligible RCTs. SLRs that included observational studies were excluded. Studies that did not use SAVR in the control group were excluded. Narrative reviews that did not report any search strategy or that did not critically appraise the included studies’ quality were excluded, as well as studies that focused only on devices or imaging. Only studies considering the first intervention were included, with VIV-TAVI and redo-SAVR interventions excluded.

Finally, another reviewer intervened when there was a disagreement between the authors.

Inclusion process

SLR reporting at least one review of clinical effectiveness/complication indicators have been considered for inclusion.

Step 1 – screening of titles and abstracts

Titles and abstracts of the references found ( n  = 2,483) were screened independently by meta-reviewers (CA, SM, GM, and LP), to check whether these publications satisfied the inclusion criteria. In this phase, the two reviewers agreed in virtually 100% of the cases. For the references selected by both reviewers and those selected by only one reviewer (a total of 85), we tried to track down or download the full text.

Step 2 – screening based on full texts

Next, the full texts were assessed independently by the first and second meta-reviewer (CA and SM or GM) using the inclusion criteria cited. In this phase, we conducted a manual search in the reference lists of the full-text papers.

The full texts of these additional references were studied as well, which brings the total number of full texts examined to 96.

Data extraction and Quality Assessment

Four reviewers (SM, LP, GM, and CA) independently extracted data/items including citation details; objectives of the included review; type of review; participant details; setting and context; the number of databases sourced and searched; date range of database searching; the number of studies, types of studies and country of origin of studies included in each review; instrument used to appraise the primary studies and the rating of their quality; outcomes reported that are relevant to the overview of systematic literature reviews (OoSRs) question; method of synthesis/ analysis used to synthesize the evidence; major conclusions; comments or notes by the OoSRs authors; metric used and effect size (for meta-analyses); Coefficient intervals Cis (for meta-analyses). Authors were contacted in case of missing data. If the requested data could not be retrieved, the study was not included in the analysis. A Measurement Tool to Assess Systematic Reviews (AMSTAR) [ 5 ] was adopted to perform a rapid and reproducible critical assessment of the methodological quality of the included studies. Finally, studies whose methodological quality was judged to be critically low according to the AMSTAR assessment tool were excluded.

Figure  1 summarizes the screening process. We found 33 SLRs (Appendices 2 in the Data Supplement). All the included studies were published between 2013 and April 2024 in English. Overall, 22 SLRs collected their data only from Randomized Controlled Trials (RCTs), whereas 11 SLRs collected data from randomized and non-randomized studies and prospective or retrospective observational studies.

Workflow for the selection of eligible studies following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria

Twenty-three studies considered elderly patients, over 65 years old. Sixteen studies included all surgical STS-risk patients. Low, low to intermediate, intermediate, and high risk were considered in 9, 2, 3, and 2 studies respectively. Figure  2 shows the evolution of the risk class of patients included in studies over time. Table  1 summarizes clinical outcomes results for TAVI compared to SAVR, whereas Table  2 summarizes complications regarding included studies.

Distribution of risk classes included in studies per different years. The figure reports the number of studies including All risks of patients, high, intermediate, low to intermediate, and low risk distribution per year. *The year 2023 includes also one paper published in 2024

Clinical outcomes

Early mortality.

Early mortality is defined as mortality at 30 days or in-hospital in fourteen studies [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ], as 3-month mortality in one study [ 20 ] and as 6-month mortality in another study [ 21 ]. Only one study did not define the time interval considered [ 22 ].

Early mortality was evaluated in eighteen out of the thirty-three studies included. Ten studies [ 6 , 8 , 9 , 13 , 15 , 16 , 17 , 18 , 20 , 22 ] found early mortality to be similar in both TAVI and SAVR groups. Five studies [ 10 , 11 , 14 , 19 , 21 ] found TAVI to be associated with lower rates of early mortality. In one study [ 7 ], early mortality for TAVI vs. SAVR was found to be lower in patients with chronic kidney disease (CDK), whereas another study [ 12 ] assessed better outcomes for TAVI vs. SAVR in women. Lastly, one study reported lower rates of early mortality for low-risk patients and similar rates for high-risk patients [ 23 ].

Late Mortality

Late mortality was identified with mortality at 1 year of follow-up for most of the studies included [ 6 , 8 , 10 , 11 , 12 , 15 , 16 , 20 , 23 , 24 , 25 ] whereas five studies [ 13 , 17 , 18 , 21 , 26 ] considered two years. One study [ 19 ] reported late mortality for a follow-up period of 5 years. Two studies [ 14 , 17 ] did not report the time interval for this outcome, and one study [ 22 ] considered more than 1 year.

Late mortality was evaluated in twenty out of the thirty-three studies included and was found to be similar between TAVI and SAVR in eleven studies [ 6 , 8 , 9 , 11 , 15 , 17 , 18 , 20 , 22 , 23 , 24 , 25 , 26 ]. One study [ 12 ] reported lower mortality rates for TAVI in medium-risk women. Two studies [ 10 , 16 ] found TAVI to be associated with lower mortality overall, considering low surgical-risk patients. Four studies [ 13 , 14 , 19 , 21 ] favoured SAVR over TAVI, all three including patients with all surgical risks. One study [ 23 ] found mortality to be lower for TAVI in patients with high surgical risk and similar to SAVR for low surgical risk patients.

All-Cause mortality

Eleven studies evaluated all-cause mortality; four [ 24 , 27 , 28 , 29 ] found that it was similar between TAVI and SAVR, whereas two studies [ 30 , 31 ] reported a lower rate for TAVI in the first year and similar rates in the second year of follow-up. Two studies favored SAVR [ 32 , 33 ], and one study [ 34 ] reported a lower mortality for TAVI in the first follow-up year, which becomes equal to SAVR in the second year until it worsens between years two and five.

Cardiac mortality

Cardiac mortality was specifically evaluated in six out of the thirty-three studies included. Four [ 18 , 24 , 27 , 35 ] studies found cardiac mortality to be similar between TAVI and SAVR. Two studies [ 29 , 36 ] favored SAVR over TAVI and one [ 30 ] reported a lower rate for TAVI in the first year and similar rates in the second year of follow-up. One study [ 34 ] reported similar rates in the first year of follow-up, higher rates in the second year for TAVI, and similar rates until year five of follow-up.

Stroke and transient ischemic attacks (TIA)

Twenty-four studies out of the thirty-three selected evaluated the risk of stroke. Sixteen studies [ 6 , 8 , 11 , 13 , 14 , 15 , 16 , 22 , 24 , 26 , 27 , 28 , 29 , 34 , 36 , 37 , 38 ] found the hazard for stroke to be similar between TAVI and SAVR. Two studies [ 9 , 18 ] found TAVI to have a higher rate of stroke than SAVR, with the first study considering only high-risk surgical patients and the second one including patients with all risk classes. Four studies [ 21 , 25 , 31 , 39 ] found TAVI to be associated with a lower incidence of stroke. Of those, three included patients with all classes of surgical risk and one included only low surgical risk patients.

One study [ 7 ] found TAVI to be favorable in patients with CDK, whereas another one [ 23 ] reported lower incidence in patients with low surgical risk and similarities between TAVI and SAVR in high surgical risk patients.

Two studies out of the thirty-three selected evaluated the risk of developing TIA, one [ 18 ] found similarities between TAVI and SAVR, whereas the other one reported a lower rate of TIA with TAVI.

Myocardial infarction

Thirteen studies out of the thirty-three selected evaluated the occurrence of periprocedural myocardial infarction. Ten studies [ 6 , 8 , 11 , 13 , 14 , 15 , 16 , 18 , 26 , 29 ] reported similarities between TAVI and SAVR. Three studies [ 20 , 27 , 31 ] found TAVI to be associated with lower rates of myocardial infarction.

Complications

Major bleeding.

Sixteen studies out of the thirty-three selected evaluated the risk of significant bleeding complications. Twelve studies [ 8 , 9 , 10 , 16 , 18 , 22 , 25 , 26 , 28 , 29 , 30 , 35 , 37 ] found TAVI to be associated with lower rates of major bleeding. One study [ 23 ] found TAVI to be less favourable than SAVR and two studies [ 6 , 13 ] reported similarities between TAVI and SAVR.

One review [ 8 ] reported that, in the early days of TAVI, bleeding was the most common complication resulting from the use of large bore sheaths. However, advancements in percutaneous techniques, ultrasound guided vascular cannulation, smaller catheter systems, and operator experience have reduced periprocedural bleeding in TAVR over time.

Acute kidney injury (AKI)

Eighteen studies out of the thirty-three selected evaluated the risk of developing acute kidney injury. Sixteen studies [ 7 , 8 , 10 , 11 , 13 , 14 , 16 , 20 , 22 , 25 , 26 , 27 , 28 , 29 , 30 , 35 ] found TAVI to be associated with a lower incidence of AKI. One study [ 15 ] found similarities between TAVI and SAVR. One study [ 23 ] reported a higher incidence of AKI in TAVI patients.

Vascular complication

Twelve studies out of the thirty-three selected evaluated the risk of developing vascular complications. Nine studies [ 9 , 11 , 13 , 14 , 16 , 20 , 22 , 25 , 29 ] found TAVI to be associated with a higher incidence of vascular complications. One study [ 27 ] reported similar results between TAVI and SAVR, and another study [ 7 ] was neutral in patients with CDK. One study [ 23 ] favoured TAVI over SAVR for the development of vascular complications.

Pacemaker implantation

Twenty-two evaluated the rate of pacemaker implantation after the procedure. Eighteen studies [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 22 , 25 , 26 , 27 , 28 , 29 , 30 ] found TAVI to be associated with a higher risk of pacemaker implantation (PI), whereas one [ 24 ] found similarities between TAVI and SAVR. One study [ 23 ] reported TAVI to be associated with lower rates of pacemaker implantation. One study found TAVI to be associated with a lower risk of PI in the first two years after the operation, and similar rates from year 20 to year 5.

Subgroup analyses were performed by some authors to discern the risk of pacemaker implantation by valve type, comparing Self-Expanding VALVES (SEV) versus Balloon-Expandable (BEV) valves.

Four studies [ 6 , 10 , 11 , 27 ] found that within TAVI procedures, BEV had a lower incidence of PI, whereas one study [ 17 ] found that mechanically-expandable valve (MEV) was associated with an increased risk of pacemaker implantation compared to BEV, SEV, and SAVR in the long term.

Residual aortic regurgitation and moderate-severe paravalvular leak

Seven studies [ 6 , 9 , 15 , 16 , 22 , 25 , 27 ] out of the thirty-three selected evaluated the complication of residual aortic regurgitation, all reported higher rates associated with TAVI interventions.

Six studies out of the twenty-seven selected evaluated moderate-severe paravalvular leaks. All six [ 12 , 15 , 16 , 20 , 24 , 28 ] reported TAVI to have a higher incidence than SAVR, with one study [ 12 ] detailing a better outcome specifically for male patients.

Atrial fibrillation

Eleven studies out of the thirty-three selected evaluated the development of new-onset atrial fibrillation. Ten studies [ 6 , 8 , 10 , 11 , 15 , 26 , 27 , 28 , 30 , 35 ] found TAVI to be associated with a lower incidence, whereas one study [ 23 ] found TAVI to be less favourable than SAVR. Another study [ 31 ] found similar rates between TAVI and SAVR.

Five studies out of the thirty-three selected evaluated the development of atrial fibrillation. All studies [ 16 , 24 , 25 , 29 , 31 ] found TAVI patients to have lower rates of atrial fibrillation.

Conclusions

To the author’s knowledge, the present study is the first effort to summarize the evidence in an overview of SRs (OoSRs) focusing exclusively on secondary studies that have reported at least one review of clinical outcomes/process indicators. Hence this study summarizes the findings of existent literature reviews on the performance of TAVI in the last 10 years providing a rapid picture of the evolution of TAVI over time on the main KPIs. Our work shows that older reviews from 2013 to 2020 focused on high-risk patients, while since 2020 both high and low-risk patients were considered. There is a need to point out that reviews considering all risk classes of patients, did not report the results grouped by risk class. Accordingly, only one study reported the results for men and women separately. Regarding the included patients’ age, no reviews reported results broken down by age group. The authors recognize that by applying exclusion criteria, such as excluding systematic literature reviews containing observational studies or those solely focused on devices or imaging, there is a potential for narrowing the scope of the review. This narrowing could result in overlooking valuable insights from specific study designs or aspects of TAVI, which should be acknowledged as a limitation of the study. Still, the focus of this OoSRs was to identify and select relevant KPIs on selected outcomes and complications and not to compare devices.

AKI and new-onset atrial fibrillation showed a better performance overall for TAVI in comparison to SAVR. Other indicators suggest that TAVI presents a higher incidence of complications such as pacemaker implantation and vascular complications with respect to SAVR. Both early and late mortality showed no significant difference between the two procedures initially. For late mortality, a noticeable shift in the studies included emerges from 2022 onwards. Initially, both groups showed comparable mortality rates. However, in recent studies, TAVI demonstrates a higher mortality rate. Regarding patient risks, no distinctions were found among high-risk patients for both early and late mortality, while two studies observed lower early mortality rates for low-risk patients. The shift in included studies from 2022 onwards underscores the need for further investigation, particularly given the relative youth of the TAVI procedure. Medical devices and surgical procedures are historically associated with learning curves, meaning that the performance changes over time while the operators gain experience and refine their performing techniques. Additionally, advancements in imaging technologies, such as 3D echocardiography and intravascular ultrasound, have enhanced procedural guidance and accuracy.

The evolution of TAVI techniques over time has allowed for an expansion of the criteria for patient selection. Initially, only patients deemed inoperable for traditional open-heart surgery due to prohibitive surgical risks, comorbidity, and age underwent TAVI procedures. There has recently been an expansion of indications to intermediate and low-risk patients as well, based on clinical evidence and individual patient characteristics. Over time, a reduction in procedural complications and device-related complications such as paravalvular leakage and vascular complications, have been minimized with improved device designs and operator experience. Whereas surgical valves have a long-established track record, TAVI valves have been continuously improving in terms of design, durability, and longevity. Current research is focused on evaluating the durability and longevity of such valves in order to ensure maximum comfort to patients and lower rates of complications.

A long-term assessment of valve durability has only been possible in recent years, and few papers have investigated the differences between transcatheter and surgical bioprostheses. One study [ 40 ]revealed that TAVI valves exhibited a higher susceptibility to structural valve deterioration, while another study [ 41 ] indicated that the rate of moderate/severe structural valve deterioration was greater in SAVR cases, with similar rates of bioprosthetic valve failure between the two groups. It’s essential to acknowledge that TAVI is a newer technology compared to SAVR, thus still undergoing an evolution in terms of designs and enhancements.

Compared to open-heart surgery, TAVI requires smaller incisions and reduces the need for sternotomy. The minimally invasive nature of TAVI contributes to sustainability by minimizing patient discomfort and allowing for a quicker return to daily activities. Additional studies regarding the sustainability of the intervention and long-term durability of the implanted valves should be carried out in order to fully assess the potential for TAVI interventions. In conclusion, the evolution of TAVI seems an ongoing process, with current research and development, focused on improving patient outcomes, expanding indications, and addressing potential limitations.

Data availability

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The research was carried out as a part of the NET-2018-12368077 project funded by the Tuscany Region and Italian Ministry of Health.

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CA contributed to the acquisition of data, the analysis of data, the interpretation of results, and the writing of the article. GM contributed on the acquisition of data, the analysis of data, and the writing of the article. SM contributed to the acquisition of data. LP contributed to the interpretation of results and the writing of the article. MV and CP contributed to the concept of the study, the interpretation of results, and the critical revision of the paper.

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Angioletti, C., Moretti, G., Manetti, S. et al. The evolution of TAVI performance overtime: an overview of systematic reviews. BMC Cardiovasc Disord 24 , 314 (2024). https://doi.org/10.1186/s12872-024-03980-2

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Received : 25 October 2023

Accepted : 14 June 2024

Published : 21 June 2024

DOI : https://doi.org/10.1186/s12872-024-03980-2

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