Systematic Literature Review: What It Is and How to Conduct One

A systematic literature review is often mentioned alongside standard literature reviews as if the two are interchangeable, but they follow genuinely different processes with different standards of rigor. This guide explains what actually distinguishes a systematic review, and the real steps involved in conducting one properly.

What Makes a Review "Systematic"

A standard (or narrative) literature review synthesises relevant sources around themes, guided by the researcher's judgement about which sources are important and relevant. A systematic review instead follows a predefined, explicit, and reproducible protocol for finding, screening, and including studies - the goal being that another researcher, following your same protocol, would identify largely the same set of studies.

This distinction matters because a systematic review is making an implicit claim of comprehensiveness and reduced bias that a narrative review does not make. A narrative review says "here is my informed synthesis of the relevant literature." A systematic review says "here is what the entire identifiable body of literature on this specific question shows, found through a documented, replicable search process."

The Core Steps of a Systematic Review

1. Define a focused research question. Systematic reviews typically use a structured question format - PICO (Population, Intervention, Comparison, Outcome) is common in health and clinical fields, though other structured frameworks exist for other disciplines. A vague question like "does exercise help mental health" is not systematic-review-ready; "does aerobic exercise, compared to no intervention, reduce depressive symptom severity in adults with major depressive disorder" is.

2. Develop and document explicit inclusion and exclusion criteria. Before searching, you define exactly what makes a study eligible - publication date range, study design, population characteristics, language, and any other relevant criteria. This step happens before searching, not after, precisely to reduce the risk of selectively including studies that support a preferred conclusion.

3. Conduct a comprehensive, documented search. This means searching multiple relevant databases (not just one), using a documented and ideally reproducible search string, and recording exactly how many results each search returned. The search strategy itself is typically reported in enough detail that another researcher could rerun it.

4. Screen results against your criteria in two stages. Titles and abstracts are screened first to eliminate clearly irrelevant results, followed by full-text screening of the remaining studies against your full inclusion and exclusion criteria. Many systematic reviews use two independent reviewers for this screening stage specifically to reduce individual bias, though this depends on the scale of the review and available resources.

5. Extract data systematically. Relevant information from each included study - methodology, sample size, key findings, and whatever else is relevant to your specific research question - is extracted using a consistent, predefined extraction form, rather than being pulled inconsistently as you read.

6. Assess the quality of included studies. Not all studies that meet your inclusion criteria are equally rigorous. A systematic review typically includes some structured quality or risk-of-bias assessment of each included study, and this assessment often informs how much weight different studies are given in your synthesis.

7. Synthesise the findings. Depending on the nature of the included studies, this synthesis might be narrative (thematic synthesis of qualitative or heterogeneous findings) or statistical (a meta-analysis, if the included studies are similar enough quantitatively to be statistically combined).

Reporting Standards: PRISMA

Most systematic reviews now follow PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines, which specify exactly what information a systematic review write-up should include - a checklist covering everything from how the search was conducted to how many studies were excluded at each stage and why.

A key visual element associated with PRISMA is the flow diagram, which shows the number of records identified, screened, excluded (with reasons), and ultimately included at each stage of the process. This diagram is now close to a standard expectation for systematic reviews in most fields, since it gives readers an immediate, transparent view of your selection process.

Systematic Review vs Narrative Review: When to Use Which

A systematic review is the right choice when your research question can be framed narrowly and precisely enough to support a defined search protocol, when comprehensiveness and reduced selection bias are genuinely important to your research goals, and when you have the time and resources the process demands - a proper systematic review is significantly more time-intensive than a narrative literature review.

A narrative review remains the right and appropriate choice for broader theoretical questions, for literature reviews serving as a single chapter within a larger dissertation (where comprehensive systematic methodology for every possible sub-topic is rarely feasible), or when the goal is contextual synthesis rather than answering one narrowly defined empirical question.

Many dissertation students mistakenly believe a systematic review is always the more rigorous or more impressive choice, when in fact the right choice depends entirely on the nature of your research question - forcing a broad, exploratory question into a systematic review's narrow structure produces a worse result than an appropriately conducted narrative review.

A Common Mistake: Calling a Review "Systematic" Without the Process

A frequent error, particularly in dissertations, is labelling a literature review "systematic" simply because it was thorough, without actually following the defined protocol - documented search strategy, explicit inclusion and exclusion criteria, two-stage screening, and typically a PRISMA-style flow diagram. Examiners familiar with systematic review methodology will notice this gap quickly, and it is generally safer to accurately describe a thorough narrative review as exactly that, rather than claiming systematic methodology you have not actually followed.

What a Systematic Review Costs You in Time

Students considering a systematic review for a dissertation should weigh the time cost honestly against a narrative review before committing. Comprehensive multi-database searching, two-stage screening (ideally with a second reviewer), structured data extraction, and quality assessment across potentially dozens of studies is a substantially larger undertaking than synthesising a smaller, purposively selected set of sources narratively. This is not a reason to avoid systematic reviews where they are genuinely the right methodological choice, but it is a real practical factor worth discussing with your supervisor early, particularly against a fixed dissertation deadline.

Getting Support With Your Systematic Review

Conducting a genuine systematic review - with a properly documented search strategy, defensible screening process, and PRISMA-compliant reporting - is a demanding undertaking that benefits enormously from a second set of eyes at each stage. If you want feedback on your protocol, search strategy, screening documentation, or final write-up, CampusScribe's editors work with systematic reviews across every stage, from initial protocol design through to final submission.

From choosing a topic to polishing a final draft, CampusScribe's subject-specialist editors and coaches help with dissertations, capstone projects, presentations, and more - whether you need topic guidance, structural feedback, or a final edit before your deadline.