The association between multiple environmental exposures and symptoms of generalized anxiety disorder in a prospective, U.S.-based cohort study.

BACKGROUND Emerging evidence has implicated built and natural environmental exposures in the etiology and exacerbation of anxiety symptoms. OBJECTIVES Our objective was to assess individual and joint associations between neighborhood socioeconomic status (nSES), walkability, greenness, fine particulate matter (PM2.5), nitrogen dioxide (NO2), and temperature and generalized anxiety disorder (GAD) symptoms. METHODS We included 81,897 participants of the Nurses' Health Study II. GAD symptoms were measured in 2013 and 2017 using the 7-item Generalized Anxiety Disorder scale (GAD-7). Walkability and nSES z-scores were calculated at the Census tract level. Normalized Difference Vegetation Index (NDVI) summer and annual average greenness at 270m and 1230m buffer sizes, and spatiotemporal models predicted one-, three-, and twelve-month averages of PM2.5, NO2, and temperature were calculated at the residence. Longitudinal logistic and generalized estimating equations (GEE) models estimated odds ratios and 95% confidence intervals for clinically relevant GAD symptoms (GAD-7 ≥ 5 points). We assessed effect modification by nSES, summer NDVI (1230m), and select covariates. We employed quantile g-computation to more directly assess the association between environmental exposure mixtures and GAD symptoms. RESULTS In single exposure models, summer NDVI (e.g., for 1230m, OR: 0.96, 95% CI: 0.94, 0.98), NO2 (e.g., for twelve-month average NO2, OR: 1.03, 95% CI: 1.01, 1.04), twelve-month average temperature (OR: 1.05, 95% CI: 1.03, 1.07, and walkability (OR: 1.02, 95% CI: 1.01, 1.03) were associated with GAD symptoms. In the joint exposure model, nSES (OR: 0.96, 95% CI: 0.95, 0.98) and summer NDVI were associated (OR: 0.92, 95% CI: 0.88, 0.96); all other associations were attenuated. Associations with summer NDVI (1230m), temperature, and NO2 were modified by nSES, with stronger associations in socioeconomically deprived areas. DISCUSSION In this population, higher levels of summer greenness and nSES may be protectively associated with GAD symptoms, while medium- and long-term NO2 exposure, long-term temperature, and walkability are adversely associated with GAD symptoms. Socioeconomically deprived areas may bear additional risks. The results of the quantile g-computation analysis suggest that environmental exposures may act antagonistically with one another in relation to GAD symptoms. https://doi.org/10.1289/EHP14458.