A systematic review is not empirical research in the traditional sense, because it does not collect new, original data through observation or experimentation. It synthesizes existing empirical studies. However, the answer is more nuanced than a simple yes or no, and how a systematic review gets classified depends on context, methodology, and who you ask.
What Makes Research “Empirical”
Empirical research is based on observed and measured phenomena. It derives knowledge from actual experience rather than from theory or belief. The hallmarks include a specific research question, a defined population or phenomenon being studied, a reproducible methodology, and results presented as data. Empirical studies typically follow the IMRaD format: introduction, methodology, results, and discussion.
By this definition, a randomized controlled trial, a survey study, or a lab experiment clearly qualifies. Researchers design a study, collect data from the real world, analyze it, and report findings. The key test is straightforward: did the researchers generate new observations?
Where Systematic Reviews Fit
A systematic review asks a focused question and then searches for every relevant study that has already been published on that topic. Researchers define eligibility criteria, run structured searches across multiple databases, screen results using independent reviewers, assess the quality of each included study, and extract data using standardized methods. When the data allows, they combine results from many studies into a single statistical estimate through meta-analysis.
This process is rigorous, transparent, and reproducible. It follows a predefined protocol, uses specific analytical tools, and produces quantifiable results. In those ways, it mirrors the structure of empirical research. But the raw material is other people’s data, not new observations collected firsthand.
This is why systematic reviews are typically classified as secondary research. They don’t observe patients, run experiments, or measure outcomes directly. They analyze and synthesize the work of primary studies. A narrative review does the same thing in principle, but without the structured methodology, which makes narrative reviews far more vulnerable to the author’s selection bias and subjective interpretation.
The Case for Calling Them Empirical
Despite being secondary, systematic reviews share several features with empirical work that blur the line. The methodology is explicit and reproducible. The data extraction process is systematic and documented. When meta-analysis is involved, new statistical findings emerge that no individual study produced, such as pooled effect sizes, overall prevalence estimates, or measures of consistency across studies. These are genuinely new quantitative results derived from a structured analytical process.
Many academic journals reinforce this view. A 2025 study in Cochrane Evidence Synthesis and Methods found that 14 journals across nine publishers classify systematic reviews under their guidelines for original research, simply stating that “systematic reviews are reported as original research.” This editorial treatment places them alongside clinical trials and observational studies rather than alongside opinion pieces or traditional literature reviews.
The evidence hierarchy also positions systematic reviews at the very top, above individual randomized controlled trials, cohort studies, case reports, and expert opinion. Some researchers describe this as a distinction between “filtered” evidence (systematic reviews and meta-analyses) and “unfiltered” evidence (individual trials and observational studies), with filtered evidence considered the most reliable. It would be unusual to place a non-empirical study type above all empirical study types in a hierarchy meant to rank the strength of scientific evidence.
Why the Distinction Matters
If you’re a student trying to figure out whether a systematic review counts toward an assignment requiring “empirical sources,” the answer depends on your instructor’s definition. Some professors use “empirical” strictly to mean primary data collection. Others accept systematic reviews because they apply a scientific method to produce new findings from existing data. Ask for clarification before assuming either way.
If you’re evaluating the strength of evidence for a health decision, systematic reviews are generally more trustworthy than any single empirical study. A well-conducted systematic review following PRISMA guidelines requires a full, transparent search strategy, independent screening by multiple reviewers, formal assessment of bias in each included study, and reporting of the overall certainty of evidence (rated as high, moderate, low, or very low) for each outcome. That level of rigor often exceeds what you’ll find in a single trial.
How Systematic Reviews Differ From Narrative Reviews
The distinction between systematic and narrative reviews is important here, because narrative reviews are almost universally considered non-empirical. A narrative review lets the author select studies based on personal judgment, with no requirement for comprehensive searching or transparent inclusion criteria. As one analysis in Psychiatry Investigation put it, narrative reviews “may be evidence-based, but they are not truly useful as scientific evidence” because they are too selective and lack methodological rigor.
Systematic reviews were developed specifically to address those weaknesses. They require predefined protocols, exhaustive database searches regardless of whether results favor a particular conclusion, transparent selection criteria, and formal quality assessment of every included study. This structured, reproducible approach is what gives systematic reviews their scientific credibility and what makes their classification as research, rather than mere summary, defensible.
The Practical Answer
A systematic review occupies a unique middle ground. It is not primary empirical research because it does not collect original data. But it is not a simple literature summary either. It applies a scientific method to existing evidence and, particularly when it includes meta-analysis, generates new quantitative findings. Most researchers and many journals treat systematic reviews as a form of original research, and the evidence hierarchy places them at the highest level of scientific reliability. Whether you call that “empirical” depends on how narrowly you define the term.