Long-term ambient air pollution and the risk of major mental disorder: A prospective cohort study.

Background: Despite growing awareness of the mental health damage caused by air pollution, the epidemiologic evidence on impact of air pollutants on major mental disorders (MDs) remains limited. We aim to explore the impact of various air pollutants on the risk of major MD.

Methods: This prospective study analyzed data from 170 369 participants without depression, anxiety, bipolar disorder, and schizophrenia at baseline. The concentrations of particulate matter with aerodynamic diameter ≤ 2.5 μm (PM), particulate matter with aerodynamic diameter > 2.5 μm, and ≤ 10 μm (PM), nitrogen dioxide (NO), and nitric oxide (NO) were estimated using land-use regression models. The association between air pollutants and incident MD was investigated by Cox proportional hazard model.

Results: During a median follow-up of 10.6 years, 9 004 participants developed MD. Exposure to air pollution in the highest quartile significantly increased the risk of MD compared with the lowest quartile: PM (hazard ratio [HR]: 1.16, 95% CI: 1.09-1.23), NO (HR: 1.12, 95% CI: 1.05-1.19), and NO (HR: 1.10, 95% CI: 1.03-1.17). Subgroup analysis showed that participants with lower income were more likely to experience MD when exposed to air pollution. We also observed joint effects of socioeconomic status or genetic risk with air pollution on the MD risk. For instance, the HR of individuals with the highest genetic risk and highest quartiles of PM was 1.63 (95% CI: 1.46-1.81) compared to those with the lowest genetic risk and lowest quartiles of PM.

Conclusions: Our findings highlight the importance of air pollution control in alleviating the burden of MD.