THE EVIDENCE As Syntheses systematically search and critically analyze the evidence found across multiple studies, they contain a higher level of evidence than a single study or a commentary of a single study (synopses of studies). With this tier, critical appraisal of the validity and evidence in all the studies contained in a systematic review has already been done for you. Just remember that systematic reviews typically look at a very narrow subset of a particular topic and are not overarching summaries of the literature (we'll be looking at this in Summaries).
SYSTEMATIC REVIEWS V. NARRATIVE REVIEWS V. LITERATURE REVIEWS Systematic reviews are often confused with narrative reviews (review articles) or literature reviews. Narrative reviews generally examine the literature from the author's perspective and include author commentary with no criteria for searching and including literature. Literature reviews usually try to identify trends across a subject, do not have a reproducible search or methodology, and do not attempt to appraise the validity of the articles.
KEY RESOURCES FOR LOCATING SYSTEMATIC REVIEWS