When you start exploring the research landscape on any topic, you quickly run into different types of reviews. Literature reviews, systematic reviews, scoping reviews, narrative reviews… the labels multiply, and honestly, the boundaries between them can feel blurry. As Arksey and O’Malley (2005) put it, “There do not appear to be any consistent definitions of these different review ‘animals’, with the result that researchers may use labels loosely.” (p. 20)
That looseness creates real problems. Some reviews get called “systematic” even when they skip quality appraisal or bias protection. Others claim to be comprehensive when they are really just selective summaries shaped by the author’s perspective. If you are conducting a review, teaching students how to do one, or simply trying to evaluate a study you have read, understanding what distinguishes these approaches matters.
What Is a Literature Review?
A literature review, in its traditional form, is an interpretive summary of existing research on a topic. The researcher reads widely, identifies themes and patterns, and weaves together a narrative that situates their own work within the broader scholarly conversation.
What makes traditional literature reviews distinctive is the role of author voice and expertise. The researcher selects which studies to include, decides how to frame them, and uses judgment to build an argument or establish theoretical context. Methods are often implicit. You might not find a detailed account of how databases were searched, how studies were screened, or why certain sources were included while others were left out.
This flexibility is not a flaw. Literature reviews serve important purposes: building arguments, establishing context, and supporting conceptual or theoretical work. They help readers understand how a field has developed and where key debates lie. But because the methods are not always transparent, it can be difficult for readers to judge whether the review is comprehensive or whether it reflects the author’s selective reading.
Tricco et al. (2011) frame this distinction clearly. They argue that systematic reviews prioritize transparency over author voice, while traditional literature reviews lean into interpretation and discourse. One approach is evaluative and procedural; the other is interpretive and discursive. Neither is inherently superior. The question is whether the method fits the purpose.
Related: Best Books on Research Ethics
What Is a Systematic Review?
A systematic review takes a fundamentally different approach. It begins with a clearly formulated question, often structured using frameworks like PICO (Population, Intervention, Comparison, Outcome), and follows explicit, reproducible methods for every stage of the process.
As Tricco et al. (2011) explain, “systematic reviews consist of a clearly formulated question and use systematic and explicit methods to identify, select, critically appraise, and extract and analyze data from relevant research.” (p. 11)
The emphasis on explicitness is deliberate. Systematic reviews are designed to minimize bias through protocols developed in advance, comprehensive database searching, duplicate screening by multiple reviewers, and formal risk-of-bias assessment. Every decision is documented so that another researcher could, in theory, replicate the process and reach the same conclusions.
This rigor comes with a tradeoff. Systematic reviews typically focus on narrowly defined questions and often restrict inclusion to specific study designs, particularly randomized controlled trials or other high-quality experimental evidence. The goal is not to map a broad terrain but to answer a precise question with the most reliable evidence available.
Quality appraisal is central to the process. Studies are assessed for methodological rigor, and those assessments shape how findings are weighted and interpreted. This is what allows systematic reviews to make claims about effectiveness or to inform clinical guidelines and policy decisions.
Scoping Reviews: A Third Category Worth Knowing
Before comparing literature reviews and systematic reviews directly, it helps to understand scoping reviews, which occupy a middle ground that often gets overlooked.
Colquhoun et al. (2014) define a scoping review as “a form of knowledge synthesis that addresses an exploratory research question aimed at mapping key concepts, types of evidence, and gaps in research related to a defined area or field by systematically searching, selecting, and synthesizing existing knowledge.” (pp. 1293-1294)
The key word here is exploratory. Scoping reviews are designed to map the landscape of a field, especially when that field is emerging, fragmented, or conceptually diverse. They ask broad questions and intentionally include many different study designs and source types.
Unlike systematic reviews, scoping reviews usually do not assess the quality of included studies. As Arksey and O’Malley (2005) note, “A scoping study is less likely to seek to address very specific research questions nor, consequently, to assess the quality of included studies” (p. 20). This means scoping reviews cannot weigh evidence or make definitive claims about what works. Their purpose is different: to show what research exists, how it clusters, and where the gaps are.
Arksey and O’Malley (2005) capture this distinction well: “Unlike a systematic review the scoping study does not seek to ‘synthesize’ evidence or to aggregate findings from different studies” (p. 27). Instead, scoping reviews describe patterns and identify areas that might benefit from deeper investigation.
Scoping reviews can serve as a precursor to a full systematic review, helping researchers determine whether enough high-quality evidence exists to justify a more focused synthesis. Or they can stand alone as a way to summarize research activity and inform policy, practice, or future research directions.
Comparing the Approaches
| Dimension | Literature Review | Systematic Review | Scoping Review |
|---|---|---|---|
| Question type | Broad, flexible, conceptual | Narrow, focused, often PICO-structured | Broad, exploratory, mapping-oriented |
| Search strategy | Often selective, methods implicit | Comprehensive, transparent, reproducible | Systematic but inclusive of diverse sources |
| Quality appraisal | Rarely formalized | Central to the process | Typically not performed |
| Synthesis goal | Build argument, establish context | Answer specific question, assess effectiveness | Map landscape, identify gaps |
| Bias control | Limited | Explicit protocols to minimize bias | Limited |
| Primary audience | Conceptual and theoretical work | Clinical guidelines, policy, evidence-based practice | Emerging fields, policy scoping, research planning |
The distinctions matter for practical reasons. If you need to know whether an intervention works, a systematic review with quality appraisal is the right tool. If you want to understand how a field has evolved or position your own study within ongoing debates, a literature review makes more sense. If you are entering a new area and need to see what kinds of research exist before designing your own study, a scoping review can provide that map.
As Arksey and O’Malley (2005) remind us, “there is no single ‘ideal type’ of literature review, but rather that all literature review methods offer a set of tools that researchers need to use appropriately” (p. 20). The value of any review lies in how well its methods match its goals, not in the prestige of its label.
Why This Matters
The reason we have systematic reviews at all is that individual studies, taken alone, can mislead us. A single study might have methodological weaknesses, limited generalizability, or findings that reflect chance rather than a true effect. Tricco et al. (2011) argue that knowledge syntheses interpreting results across studies provide a more reliable foundation for decision-making than any individual study could.
But not every question requires that level of rigor, and not every field has the kind of evidence base that supports a tightly controlled systematic review. Recognizing the different tools available, and knowing when each one fits, is part of becoming a more thoughtful researcher and a more critical reader of research.
Here is an infographic I generated using NotebookLM based on insights from this post:
References
Arksey, H., & O’Malley, L. (2005). Scoping studies: Towards a methodological framework. International Journal of Social Research Methodology, 8(1), 19–32. https://doi.org/10.1080/1364557032000119616
Colquhoun, H. L., Levac, D., O’Brien, K. K., Straus, S., Tricco, A. C., Perrier, L., Kastner, M., & Moher, D. (2014). Scoping reviews: Time for clarity in definition, methods, and reporting. Journal of Clinical Epidemiology, 67(12), 1291–1294. https://doi.org/10.1016/j.jclinepi.2014.03.013
Tricco, A. C., Tetzlaff, J., & Moher, D. (2011). The art and science of knowledge synthesis. Journal of Clinical Epidemiology, 64(1), 11–20. https://doi.org/10.1016/j.jclinepi.2009.11.007
