Efficacy and effectiveness studies of depression are not well-differentiated in the literature: a systematic review

In the literature on the treatment of depression, efficacy and effectiveness research have different purposes and should apply different research methodologies.

The purpose of the study was to review characteristics of depression treatment studies identified using efficacy or effectiveness search terms. We considered subject inclusion and exclusion criteria; numbers of subjects enrolled and the proportion in the primary analyses; inclusion of a Consolidated Standards of Reporting Trials (CONSORT) flow diagram; use of random assignment; use of placebo control conditions; lengths of treatment and follow-up; primary outcome variable; trial registration; journal impact factor.

Studies indexed as efficacy AND 'real-world' AND depression or effectiveness AND 'real-world' AND depression in PubMed up to 18 May 2019.

27 studies met the inclusion criteria: 13 effectiveness studies, 6 efficacy studies and 8 studies indexed as both effectiveness and efficacy. Studies identified as effectiveness, efficacy, or both differed on three outcome measures: the inclusion criteria were lengthier for efficacy than for effectiveness studies; efficacy studies were more likely to have a placebo control condition than effectiveness studies; and the journal impact factor was lower for effectiveness studies than for studies from the efficacy search or studies identified by both searches.

Efficacy and effectiveness research hypothetically use different methodologies, but the efficacy and effectiveness literatures in the treatment of depression were comparable for most of the coded characteristics. The lack of distinguishable characteristics suggests that variably applied terminology may hinder efforts to narrow the gap between research and practice. PROSPERO REGISTRATION NUMBER: #CRD42019136840.