A prospective study of a whole blood metal mixture and depressive symptoms among Black women from Detroit, Michigan.

Exposure to metals has been previously associated with depressive symptoms, but few studies have considered potential effects of metal mixtures. In addition, few previous studies have been conducted among Black women, who are disproportionately at risk for exposure to some metals and greater depression incidence and severity. We analyzed data from the Study of Environment, Lifestyle, and Fibroids (SELF), a prospective cohort study of reproductive-aged Black women from Detroit, to examine associations between a mixture of metals, metalloids, and trace elements ("metals") and depressive symptoms (n = 1450). SELF participants self-identified as Black or African American and were 23-34 years of age at enrollment. We collected covariate information on structured questionnaires and whole blood samples at baseline. We quantified 17 metals in whole blood using inductively coupled plasma mass spectrometer triple quadruple or Direct Mercury Analyzer-80. Participants reported depressive symptoms on the Center for Epidemiologic Studies Depression Scale (CES-D) at the 20-month follow-up visit, where higher CES-D scores reflected greater depressive symptoms. We used quantile-based g-computation to estimate the cumulative association of the metal mixture with CES-D scores, adjusting for age, household income, educational attainment, body mass index, smoking status, alcohol intake, and parity. We estimated beta coefficients (with 95 % confidence intervals [CI]) as the percent difference in CES-D scores per quartile increase in all metals. A one-quartile increase in the metal mixture was associated with 14.8 % lower (95 % CI=-26.7 %, -1.1 %) CES-D scores, reflecting lower depressive symptoms. The mixture association was driven by nickel, copper, cesium, molybdenum, and lead. Other neurotoxic metals (cadmium, arsenic, mercury, chromium) were associated with greater depressive symptoms. Findings from this study suggest that exposure to a mixture of metals may affect depressive symptoms in Black women, with individual metals acting in opposing directions.