The Association between Multiple Environmental Exposures and Symptoms of Generalized Anxiety Disorder in a Prospective, US-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 seven-item Generalized Anxiety Disorder scale (GAD-7). Walkability and nSES z-scores were calculated at the census tract level. Summer and annual average greenness were measured using Normalized Difference Vegetation Index (NDVI) at 270 m and 1,230 m buffer sizes. 1-, 3-, and 12-month averages of particulate matter with an aerodynamic diameter of <2.5micrograms (PM2.5), nitrogen dioxide (NO2), and temperature were predicted using spatiotemporal models. Exposures were measured at the residential level. Longitudinal logistic and generalized estimating equations (GEE) models estimated odds ratios (OR) and 95% confidence intervals (CIs) for clinically relevant GAD symptoms (GAD-7 ≥5 points). We assessed effect modification by nSES, summer NDVI (1,230m), and select covariates. We employed quantile g-computation to assess the association between environmental exposure mixtures and GAD symptoms more directly.

RESULTS

In single-exposure models, summer NDVI (e.g., for 1,230m, OR=0.96; 95% CI: 0.94, 0.98), NO2 (e.g., for 12-month average NO2, OR=1.03; 95% CI: 1.01, 1.04), 12-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 (1,230m), 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, whereas 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.