A literature review is a critical and systematic examination of scholarly sources (such as books, research articles, dissertations, conference papers, and other relevant publications) on a specific topic or research question. It is a comprehensive summary and evaluation of existing knowledge, theories, and findings related to a particular subject area.
The purpose of a literature review varies depending on the context and objectives of the study. It can be conducted as a standalone work, such as a literature review paper, or as a preliminary step in a research project to establish a theoretical framework and identify research gaps. Regardless of its specific purpose, a literature review involves the following key elements:
Identification and selection of sources
Evaluation and analysis of sources
Synthesis and organisation of information
Identification of research gaps
Analysis and interpretation of findings
Conclusion and recommendations
Overall, a literature review serves as a foundation for research by establishing a context for the study, informing theoretical frameworks, and providing a comprehensive overview of existing knowledge. It aids researchers in understanding the current state of research, identifying areas for further investigation, and positioning their work within the broader academic discourse.
A. Systematic Literature Review
In research and academia, staying up-to-date with the ever-expanding body of knowledge is paramount. However, the sheer volume of scholarly publications can be overwhelming, making it difficult to extract meaningful insights. This is where systematic literature review (SLR) comes into play. A systematic literature review is a rigorous and comprehensive approach to synthesising existing research in a particular field or topic.
A systematic literature review is a systematic and transparent method for identifying, evaluating, and synthesising relevant research studies on a specific research question or topic. Unlike traditional literature reviews, which may be prone to bias and subjectivity, SLRs follow a well-defined and replicable methodology. By employing explicit search strategies and predefined inclusion and exclusion criteria, SLRs aim to minimise bias and ensure a comprehensive and unbiased review of the available evidence as depicted in the Hierarchy of Scientific Evidence by The Logic Of Science.
An SLR is a rigorous and structured approach to synthesising existing research in a specific field or topic. By following a well-defined methodology, SLRs provide researchers with a comprehensive overview of the available evidence, helping to inform decision-making, identify research gaps, and advance knowledge, as well as providing an invaluable resource for researchers, policymakers, and practitioners.
B. Types of SLR
There are several types of SLR, each with its own focus and purpose. Here are some commonly recognised types:
Traditional/Systematic review
This is the most basic type of systematic literature review.
It aims to provide a comprehensive and unbiased summary of the evidence on a specific research question or topic.
It follows a systematic methodology for searching, selecting, and evaluating studies.
Meta-analysis
A meta-analysis is a quantitative systematic review that involves statistical analysis of data from multiple studies.
It aims to synthesise and combine the results of individual studies to generate an overall effect size or estimate.
Meta-analysis is particularly useful when studies have similar designs, outcomes, and measures.
Meta-synthesis
Meta-synthesis is a qualitative systematic review method that focuses on synthesising findings from qualitative studies.
It involves analysing and interpreting the findings, themes, and concepts across multiple studies to better understand a particular phenomenon or research question.
Scoping review
A scoping review aims to map the existing literature on a broad research topic.
It provides an overview of the quantity, nature, and distribution of research in a particular field, highlighting key concepts, gaps, and emerging trends.
Scoping reviews often do not assess study quality or conduct detailed data synthesis.
Systematic mapping review
A systematic mapping review is similar to a scoping review but focuses on systematically mapping the existing literature based on predefined criteria.
It aims to identify the extent, nature, and distribution of research in a particular area, including types of studies, methodologies, and geographic coverage.
Mixed methods review
A mixed methods review combines both quantitative and qualitative studies in the review process.
It involves synthesising data from various study designs, methodologies, and data types to understand a research question or topic comprehensively.
Realist review
Realist reviews explore how and why interventions work (or do not) in specific contexts.
They focus on developing theories or models of program theory by synthesising evidence from multiple sources, including empirical studies, theoretical frameworks, and stakeholder perspectives.
Above are some of the main types of systematic literature reviews. It is important to note that the specific approach and terminology may vary across disciplines and research fields. The choice of review type depends on the research question, available evidence, and the goals of the review. Below are the steps for conducting an SLR.
C. Steps to Conduct an SLR Solutions
Question
The first step in conducting an SLR is formulating a clear, focused research question.
This question should guide the entire review process and provide a framework for selecting relevant studies.
It is crucial to ensure the research question is specific, relevant, and answerable through the available literature.
Search
A systematic and comprehensive search strategy is crucial for identifying relevant studies.
It is essential to document the search strategy to ensure transparency and replicability.
This involves identifying relevant keywords, synonyms, and controlled vocabulary terms associated with the research question.
This involves searching multiple electronic databases such as academic journals, conference proceedings, and grey literature.
Grey literature refers to materials and research produced by organisations outside traditional commercial or academic publishing and distribution channels, including government reports, conference proceedings, graduate dissertations, and unpublished clinical trials.
Electronic databases, such as PubMed, Scopus, or Web of Science, are commonly used to conduct literature searches.
Screen and select
After executing the search strategies, the retrieved studies need to be screened based on predefined inclusion and exclusion criteria.
Initially, titles and abstracts are screened to identify potentially relevant studies.
Then, a full-text assessment is conducted for the selected studies.
The inclusion criteria should align with the research question and study objectives, while the exclusion criteria help filter out irrelevant or low-quality studies.
Extract
Once the studies are selected, relevant data needs to be extracted systematically.
A standardised data extraction form should be developed to collect essential information from each study, including study design, sample size, methodology, key findings, and other relevant details.
This step ensures consistency and facilitates data analysis and synthesis in later stages.
Assess
A quality assessment ensures the included studies' reliability and validity.
This step involves evaluating each study's methodological rigour, potential biases, and overall quality.
Various tools and frameworks, such as the Cochrane Risk of Bias Tool or the Joanna Briggs Institute Critical Appraisal Checklist, can assist in assessing study quality.
Synthesise and analyse
The extracted data from the selected studies are synthesised and analysed to identify patterns, themes, and relationships.
Depending on the nature of the research question and the available data, quantitative meta-analysis and thematic analysis can be employed.
Quantitative analysis involves statistical techniques to combine data from multiple studies, while qualitative analysis involves identifying common themes and drawing meaningful conclusions.
Interpret and report
The final step of an SLR is interpreting and reporting the results clearly and transparently.
The findings should be summarised, addressing the research question and objectives.
Any limitations or biases should be acknowledged, and implications for future research and practice should be discussed.
Adhering to reporting guidelines, such as PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), is crucial to enhancing the transparency and reproducibility of the review.
The article below exemplifies an SLR application published by Elsevier Ltd. in 2023.
D. Advantages of SLR
Systematic literature reviews offer several significant benefits, making them a valuable research method in various fields. Here are some key benefits:
Comprehensive and unbiased overview
Systematic literature reviews provide a comprehensive and unbiased summary of existing knowledge on a specific topic or research question.
By systematically searching, selecting, and evaluating relevant studies, they ensure a thorough coverage of the available evidence, reducing the risk of bias and providing a balanced view of the field.
Identification of research gaps
Systematic reviews help identify gaps in the existing literature.
By synthesising and analysing multiple studies, researchers can identify areas where research is lacking or where inconsistencies and contradictions exist.
Identifying research gaps guides future research efforts and contributes to advancing knowledge.
Evidence-based decision making
Systematic reviews provide a strong evidence base for decision-making.
Policymakers, practitioners, and researchers can rely on the findings of systematic reviews to inform policy development, clinical guidelines, or the design of future studies.
They help ensure that decisions are based on the best available evidence rather than individual studies or anecdotal evidence.
Strengthens research rigour
Conducting a systematic review requires a rigorous methodology.
Systematic reviews enhance the scientific rigour of the research process by following explicit and transparent procedures, such as predefined inclusion criteria, systematic searches, and study quality assessment.
This methodology helps minimise bias, increase transparency, and improve the reliability of the findings.
Summarises and synthesises complex information
Systematic reviews distil complex and vast amounts of information into a concise, organised summary.
By synthesising findings from multiple studies, they offer a clear overview of the current state of knowledge and identify consistent patterns, trends, and relationships.
This synthesised information is valuable for researchers, practitioners, and policymakers looking to understand the topic comprehensively.
Facilitates replication and update of findings
The systematic approach followed in conducting a review ensures transparency and applicability.
By documenting search strategies, inclusion criteria, and assessment methods, systematic reviews allow others to replicate the review process.
Additionally, systematic reviews can be periodically updated to incorporate new evidence, ensuring the currency and relevance of the findings.
Reduces research duplication
Systematic reviews help prevent unnecessary duplication of research efforts.
By summarising existing evidence and identifying research gaps, they guide researchers towards areas that require further investigation.
This reduces redundancy and promotes a more efficient allocation of research resources.
Informs policy and practice
Systematic reviews are influential in informing policy development and practice guidelines.
Systematic reviews can help policymakers and practitioners make evidence-based decisions, implement effective interventions, and optimise resource allocation.
Systematic literature reviews offer a robust and structured approach to synthesising existing evidence, identifying research gaps, and informing decision-making. Their benefits extend beyond individual studies, advancing knowledge, evidence-based practice, and policy development.
E. Disadvantages of SLR
While SLR offers numerous benefits, it also comes with certain disadvantages. It is important to be aware of these potential limitations when conducting and interpreting the findings of a systematic literature review. Some disadvantages include:
Time and resource-intensive
Conducting a systematic literature review requires significant time, effort, and resources.
The process involves extensive literature searching, screening, data extraction, and analysis, which can be time-consuming and may require a team of researchers.
Publication bias
Systematic literature reviews heavily rely on published studies, which can be influenced by publication bias.
Positive results or studies with statistically significant findings are more likely to be published, leading to an overrepresentation of certain studies and potential underrepresentation of negative or null results.
Availability of literature
Access to all relevant literature may be limited due to various reasons, such as restricted access to certain databases or publications, language barriers, or publication bias.
This may result in some studies being missed or not included in the review, potentially affecting the comprehensiveness and generalisability of the findings.
Heterogeneity of studies
The studies included in a systematic literature review may vary in methodologies, sample sizes, study designs, and outcome measures.
This heterogeneity can pose challenges in data synthesis and the generalisability of findings, particularly if the studies are too diverse to be directly compared or combined.
Quality and bias of included studies
Systematic reviews depend on the quality and rigour of the studies included.
Suppose the quality of the individual studies is low or there is a high risk of bias in the included studies. In that case, it can impact the validity and reliability of the review findings.
Updating challenges
Literature is constantly evolving, and new studies are published regularly.
Keeping a systematic review up-to-date can be challenging, especially considering the time and resources required for updates.
Outdated reviews may not reflect the most current evidence and may fail to capture recent developments in the field.
Interpretation and synthesis challenges
Systematic reviews aim to synthesise and interpret the findings of multiple studies.
However, differences in study designs, methodologies, and reported outcomes can make summarising and drawing definitive conclusions challenging.
Interpreting the findings requires careful consideration of the included studies' context, heterogeneity, and limitations.
Despite these limitations, systematic literature reviews remain valuable for summarising existing evidence, identifying research gaps, and informing decision-making. Recognising and addressing these potential disadvantages can help researchers mitigate their impact and enhance the quality and reliability of the review findings.
The SLR is a systematic and comprehensive approach to synthesising existing research, providing researchers with valuable insights and informing evidence-based decision-making. By conducting systematic literature reviews, researchers can advance their knowledge and facilitate evidence-based practices and policies in their respective fields. By following the step-by-step guide outlined in this article, researchers can effectively apply the SLR methodology, ensuring rigour, transparency, and reliability throughout the review process.
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