What is a systematic review?
There are many different types of literature reviews that researchers can use (narrative reviews, rapid reviews, scoping reviews, etc.). However, systematic reviews seek to be comprehensive by identifying, appraising, and synthesizing the most relevant research evidence and adhering to guidelines on how to conduct reviews. The Cochrane Group and Campbell Collaborative organizations provide guidance on conducting systematic review research and publish reviews.
"A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. It uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993). Cochrane Handbook
"Systematic reviews use transparent procedures to find, evaluate and synthesize the results of relevant research. Procedures are explicitly defined in advance, to ensure that the exercise is transparent and can be replicated. This practice is also designed to minimize bias. They answer pre-defined research questions, attempt to be comprehensive, screen published and unpublished sources, follow clear inclusion and exclusion criteria, provide explicit search strategies, and synthesize the best available sources. Campbell Collaboration