Environmental Chemicals and Depression in US Adults

Abstract

Background: Evidence suggests that some chemicals (e.g. pesticides, phthalates, metals) may be associated with increased risk of depression, but findings are inconsistent. Additionally, no previous study investigated the individual and joint effects of multiple chemicals in relation to depression. Objective: To investigate individual and joint associations of a mixture of chemicals with depression scores and risk of depression in U.S. adults.Methods: We utilized data from the National Health and Nutrition Examination Survey (NHANES; 2005-2016) on 30,772 participants aged 18-80 years. Depression was self-reported using the Patient Health Questionnaire-9 and was analyzed both continuously and categorically. Sixty-six chemicals including phthalates, per- and polyfluoroalkyl substances (PFAS), parabens, and polycyclic aromatic hydrocarbons (PAHs), metals, thyroid antagonists, metals, pesticides were measured in blood, serum, and urine. We used Exposome Wide Association Study (ExWAS), Bayesian Kernel Machine Regression (BKMR), and SuperLearner to investigate individual and joint associations of these chemicals with depression scores and odds of depression. Results: Approximately 9% of NHANES participants were categorized as moderately/severely depressed (PHQ-9 ≥10) with a sample geometric mean of 3.27 (95% CI: 3.24, 3.31). After adjustment for important confounders, a one standard deviation (SD) increase in blood cadmium concentration was associated with 0.24 SD (95%CI: 0.15, 0.32) higher depression scores. Parabens were associated with decreased depression scores. For instance, a 1-SD increase in ethyl paraben concentrations was associated with 0.16 SD (95% CI: -0.29, -0.03) lower depression scores. When analyzing depression scores categorically, a 1-SD increase in blood cadmium concentration was associated with 22% higher odds of depression (OR 1.22; 95% CI: 1.12, 1.33). Parabens were also associated with lower odds of depression.Conclusion: This is the first study to assess individual and joint associations of a mixture of chemicals in relation to increased or decreased risk of depression.