Explainer · Plain-language

What Is a Literature Review? Definition, Types & Purpose | CASRAI

A literature review is a systematic, critical survey of existing scholarship on a research topic. It identifies what is already known, highlights gaps or contradictions in the evidence, and contextualises a new study within the field. Unlike a bibliography or annotated bibliography, a literature review synthesises and evaluates sources rather than merely listing them.

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Purpose and function

A literature review serves several purposes simultaneously. It demonstrates that the researcher has command of the field; it establishes that the proposed study does not duplicate existing work; and it identifies gaps, contradictions, or limitations in prior research that the new study is designed to address. In a dissertation, it typically precedes the methodology chapter and provides the theoretical and empirical grounding for the research questions and design. In a journal article it is condensed into an introduction that leads the reader to the study's contribution.

Types of literature review

The term covers several distinct forms. A narrative review synthesises relevant sources selectively to tell a coherent story but does not follow a systematic protocol. A systematic review applies a rigorous, reproducible search strategy and inclusion/exclusion criteria to answer a specific question — often used in health research and policy. A scoping review maps the breadth of a field without the quality appraisal of a systematic review. An integrative review combines quantitative and qualitative evidence. An umbrella review synthesises existing systematic reviews. The choice of type depends on the question, field, and resources available.

Process: search, select, synthesise

Conducting a literature review involves searching databases (such as PubMed, Scopus, Web of Science, PsycINFO) using controlled vocabulary and keyword terms; applying inclusion and exclusion criteria to select relevant sources; critically appraising their quality and relevance; and synthesising findings thematically or chronologically rather than simply summarising each source in turn. A reference manager (such as Zotero or Mendeley) helps organise sources and format citations. PRISMA flow diagrams document the search and selection process in systematic and scoping reviews.

Literature review vs bibliography vs annotated bibliography

A bibliography is simply a list of sources consulted. An annotated bibliography adds a brief summary and evaluation of each source individually. A literature review goes further: it organises and synthesises sources around themes, debates, or timelines, evaluating how they collectively inform the research question. The analysis is integrative — connections between studies matter as much as individual sources. This distinction is important because examiners and reviewers look for synthesis and critical thinking, not description.

Key facts

At a glance

Definition: A systematic, critical synthesis of existing scholarship on a topic
Core purpose: Identify gaps, contextualise research, justify the study design
Main types: Narrative, systematic, scoping, integrative, umbrella
Where used: Dissertation/thesis chapter, journal article introduction, grant applications
Process: Database search → selection → critical appraisal → synthesis
Not a list: Unlike a bibliography, it synthesises and evaluates, not just lists

Common misconceptions

What people often get wrong

Often heard: A literature review is just a list of summaries of relevant papers.

Actually: No — a literature review synthesises and critically evaluates sources, organising them around themes, debates, or timelines to show how they collectively inform the research question.

Often heard: A systematic review and a literature review are the same thing.

Actually: No — a systematic review is a specific type of literature review that follows a rigorous, pre-registered, reproducible protocol; a narrative literature review can be less structured and is typically not pre-registered.

Often heard: A literature review only requires sources that support the research hypothesis.

Actually: No — a credible literature review includes contradictory findings, competing explanations, and limitations in existing work. Selective inclusion of only supportive sources is a form of confirmation bias.

Going deeper