Definition

Systematic review

A literature review conducted as a documented method: registered question, comprehensive search, explicit criteria, and reproducible screening.

What makes it "systematic" is the auditability: a protocol (ideally registered on PROSPERO or OSF), documented search strings per database, predefined inclusion/exclusion criteria, dual screening with recorded decisions, and a PRISMA flow diagram accounting for every record.

It answers a focused question ("does X improve Y in population Z?"), where narrative reviews map broader terrain. A meta-analysis — statistically pooling the included studies — is an optional final step, feasible only when studies are similar enough.