Association of endogenous testosterone concentration with depression in men: a systematic review protocol.

Objective: The objective of this review is to examine the association between serum testosterone concentration and the presence and severity of depression in men.

Introduction: Cross-sectional and longitudinal cohort studies examining the relationship between serum testosterone concentration and depression in men have produced mixed results. There has not, however, been any prior attempt to systematically interrogate the data. Clarification of the relationship has clinical importance because depression may be under-diagnosed in men.

Inclusion criteria: This review will consider studies involving community-dwelling men who are not receiving testosterone replacement therapy. The exposure of interest reviewed will include endogenous testosterone concentration measured through validated assays. Studies measuring total and testosterone fraction concentration will be included. This review will include studies with depression or incident depression outcomes as defined by either clinical diagnosis of depression or validated self-administered questionnaire assessing depression symptomatology.

Methods: This review will follow the JBI approach for systematic reviews of etiology and risk. The following sources will be searched: PubMed, PsycINFO, Embase, the Cochrane Central Register of Controlled Trials, Australian New Zealand Clinical Trials Registry and the ISRCTN Registry. Analytical observational studies including prospective and retrospective cohort studies, case control studies and analytical cross-sectional studies published in English or other languages with English translation will be considered. Retrieval of full-text studies, assessment of methodological quality and data extraction will be performed independently by two reviewers. Data will be pooled in statistical meta-analysis, where possible.

Systematic review registration number: PROSPERO CRD42018108273.