This is a question often posed by our science and social science students, so I like to refer to Cochrane Library for definitions:
“A systematic review is a high-level overview of primary research on a particular research question that tries to identify, select, synthesize and appraise all high quality research evidence relevant to that question in order to answer it” (Cochrane, 2014)
Another definition they give is:
“A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making” (Cochrane, 2014).
Systematic reviews are also a type of journal article, published alongside primary research articles in scholarly journals.
How do you know if a journal article is a systematic review?
Systematic reviews will identify themselves as such in the abstract, introduction, and/or the methods (sometimes even in the title). For example, you could find language like “the purpose of this systematic review…” like the example below
Systematic reviews will also often include a methods section: the authors will list what databases they searched, what terms or keywords they used, the kinds of articles they included and excluded, etc. I’ve included an example below from the open-access Journal of Neurosciences in Renal Practice:
Reviews that are not systematic don’t have these distinguishing features. If you’re not sure what kind of article something is, make sure to ask a librarian or your professor.
When would you want to use a systematic review?
Even though systematic reviews are secondary sources they are often considered more credible than regular literature reviews: this is because the authors have systematically found every article that falls into their research parameters. In a regular literature review, we can’t be sure if the authors have missed important research.
Systematic reviews are a great way to start off your research: if you’re able to find one on your exact topic, you can thank your lucky stars! We recommend students use the reference lists from systematic reviews to help identify primary research on their topics. Rather than digging through databases to get an overview on your topic, systematic reviews provide a starting list of primary research articles that you can then go find. Then you can just fill in the gaps!
That said, it’s important to pay attention to the methods of the review: what dates did they examine? Have more studies been published since the systematic review was written? Did they exclude any studies that you should probably consider? Reading a systematic review carefully will help you with determining what research you need to do next.
When should you not use a systematic review?
Systematic reviews are still secondary sources: the authors are not contributing new information or understanding to the field, but rather summarizing and combining the results of others’ research. Even though the authors take efforts to eliminate bias, there is no guarantee they have analyzed the studies correctly or from your perspective on the topic (they’re still humans, after all). Make sure to read them with a critical eye. If your professor has asked you to use primary research only, make sure to ask before using a systematic review in your reference list.