Every research project needs a literature review. But not all literature reviews are the same. Some are written as a broad, narrative overview of a topic. Others follow a strict, transparent and replicable procedure for finding, selecting and evaluating studies. The second type is called a systematic literature review, and it has become increasingly common in business, management, education, health and the social sciences.
This post explains what a systematic literature review is, how it differs from a traditional (narrative) review, the main steps involved, and how to decide which type is right for your thesis or article.
What is a traditional literature review?
A traditional or narrative literature review summarises and discusses existing research on a topic. The author selects sources they consider relevant, organises them into themes, and builds an argument that leads to a research gap or research questions.
Traditional reviews are valuable because they are flexible and allow the author to bring together ideas from different fields. Their main weakness is that the search and selection process is usually not reported in detail. Readers cannot easily tell how the author found the sources, why some studies were included and others were left out, or whether important studies were missed. This makes the review harder to replicate and more open to selection bias.
What is a systematic literature review?
A systematic literature review (SLR) answers a clearly defined review question by identifying, selecting, appraising and synthesising all relevant studies using a pre-planned, explicit and reproducible method. Every step is documented so that another researcher could repeat the process and arrive at a similar set of studies.
Systematic reviews were first developed mainly in medicine and health research, through organisations such as Cochrane. They have since been adapted for management, education, information systems and other fields.
Key differences at a glance
- Purpose: a traditional review gives a broad overview and builds an argument; a systematic review answers a specific, focused question.
- Question: traditional reviews often start with a general topic; systematic reviews start with a precise review question.
- Search strategy: traditional reviews rarely report how sources were found; systematic reviews define databases, search strings and date ranges in advance and report them in full.
- Selection: traditional reviews rely on the author's judgement; systematic reviews use explicit inclusion and exclusion criteria.
- Quality appraisal: traditional reviews seldom assess study quality formally; systematic reviews usually appraise the quality or risk of bias of included studies.
- Synthesis: traditional reviews use narrative discussion; systematic reviews use structured narrative synthesis, thematic synthesis or, where suitable, meta-analysis.
- Transparency and replicability: low in traditional reviews; high in systematic reviews.
- Time and effort: traditional reviews are quicker; systematic reviews usually take several months.
The main steps in a systematic literature review
1. Define a focused review question
A good review question sets clear boundaries. Many researchers use a framework to structure the question. PICO (Population, Intervention, Comparison, Outcome) is common in health research. In social sciences, adapted frameworks such as SPIDER or PICo are sometimes used. For example: "What factors influence the adoption of e-learning by university lecturers in developing countries?"
2. Write a review protocol
The protocol describes your question, search strategy, inclusion and exclusion criteria, quality appraisal method and synthesis approach before you start. Registering the protocol, for example on PROSPERO for health-related reviews or on the Open Science Framework, helps show that you did not change your methods after seeing the results.
3. Develop and run the search
Identify keywords and synonyms, combine them with Boolean operators (AND, OR, NOT) and run the search in several relevant databases, such as Scopus, Web of Science, ERIC, PsycINFO, Business Source or PubMed, depending on your field. Record the exact search strings, databases, dates and number of results.
4. Screen the studies
Remove duplicates, then screen titles and abstracts against your criteria, followed by full-text screening. Ideally, two reviewers screen independently and resolve disagreements by discussion. Keep a record of how many studies were excluded at each stage and why.
5. Appraise study quality
Use an appropriate appraisal tool for the types of studies you include. Examples include the CASP checklists, the Mixed Methods Appraisal Tool (MMAT) and the JBI critical appraisal checklists. Quality appraisal helps you judge how much confidence to place in the findings.
6. Extract the data
Use a data extraction form to record key details from each study, such as authors, year, country, sample, design, variables or themes, and main findings. A spreadsheet is usually enough for this step.
7. Synthesise the findings
Choose a synthesis approach that fits your data. If studies are similar enough in design and measures, meta-analysis can combine their results statistically. More often in management and education, researchers use narrative or thematic synthesis to identify patterns, contradictions and gaps.
8. Report transparently
The PRISMA 2020 statement is the most widely used reporting guideline. It includes a checklist and a flow diagram showing how many records were identified, screened, excluded and included. Following PRISMA makes your review easier to evaluate and more likely to be accepted by journals.
Other types of structured reviews
Between a fully systematic review and a traditional review, there are several other review types you may come across:
- Scoping review: maps the extent and nature of research on a broad topic, often without quality appraisal. PRISMA-ScR is used for reporting.
- Systematic mapping study: classifies the literature to show where research is concentrated and where gaps exist.
- Integrative review: combines studies with different designs, including theoretical and empirical work.
- Rapid review: follows a simplified systematic approach when time is limited.
- Bibliometric analysis: uses citation and publication data to analyse the structure of a research field.
Which type of review should you choose?
Choose a systematic review when:
- You have a focused question that existing studies can answer.
- There is enough published research to review systematically.
- Your review is a standalone paper or a major chapter of your thesis.
- You need a high level of transparency and rigour.
Choose a traditional review when:
- You need to provide background and theoretical context for an empirical study.
- Your topic is broad, interdisciplinary or conceptual.
- You want to develop a conceptual framework from diverse sources.
Many PhD theses use both: a systematic or scoping review to map the field, and a narrative review to develop the theoretical framework.
Common mistakes in systematic reviews
- Starting with a question that is too broad, leading to thousands of irrelevant results.
- Searching only one database.
- Not recording search strings and dates, making the review impossible to replicate.
- Changing inclusion criteria during screening without reporting it.
- Describing studies one by one instead of synthesising across them.
- Calling a review "systematic" when it does not follow a systematic method.
Final thoughts
The key difference between a systematic literature review and a traditional review is method. A traditional review tells a story about the literature based on the author's selection. A systematic review follows a pre-defined, transparent and replicable process to find, select, appraise and synthesise the evidence. Both are valuable. Choose the one that fits your purpose, and if you choose a systematic review, plan your protocol carefully and document every step from the start.