Social inequalities in antidepressant treatment outcomes: a systematic review

To identify, review and synthesize evidence on whether social disadvantage moderates antidepressant treatment outcomes, even when access to treatment is not a consideration.

The systematic review was done in accordance with PRIMSA guidelines. An a priori systematic search strategy was used to search databases (MEDLINE, PsychINFO, EMBASE, Global Health and Cochrane Trials Library) from their earliest entries through December 31, 2018. A two-step screening procedure was followed, and all experimental studies of antidepressant treatment in ICD/DSM diagnosed cases of depression were included. Studies with subjects < 18 years or investigating other modalities of treatment were excluded.

Thirteen papers reporting analyses from nine studies met inclusion criteria. There was heterogeneity in sample sizes, target populations, treatment settings, clinical outcomes and definition of SES indices. The primary outcome was the relative effect of socioeconomic status (SES) (as measured by income, employment status and level of education)-on antidepressant treatment outcomes.

The evidence from this review suggests that lower SES may lead to social inequalities in antidepressant treatment outcomes even in the context of clinical trials in which all participants have equal access to the same high-quality, standardized care. The review calls for more careful consideration of the choice and operationalization of SES indicators, and the need to "employ sampling methods that ensure ample representation of individuals from a wide range of social worlds". The review concludes with tentative suggestions about how to reduce social inequalities in antidepressant treatment outcomes at the level of individuals and populations.