Table 1.

Some differences between systematic and narrative reviews

Feature	Narrative review	Systematic review
Research question	Broad and informal (often not explicitly specified)	Specified and specific
Literature sources and search	Usually not specified	Comprehensive sources (more than one database) and explicit search strategy
Study selection	Usually not specified	Explicit selection criteria
Quality assessment of included studies	Usually not present or informal (not explicitly specified)	Critical appraisal on the basis of explicit criteria
Synthesis	Often a qualitative summary	Qualitative and sometimes also a quantitative summary (meta-analysis)
Time	Monthsa	>1 year (usually)
Required expertise	Science	Science, systematic review, literature searches, data analysis (including meta-analysis)
Costs	Lowa	Moderate to high

Note that these are just generalized estimates and true costs are likely to be variable for both narrative and systematic reviews

^aNarrative reviews of authorities may take years, which are associated with high costs