Differential association between ambient PM2.5 constituents and depression and anxiety among Indian adults

Ambient fine particulate matter (PM_2.5) exposure influences mental disorders, yet the differential effects of its chemical constituents remain poorly understood in low-and middle-income countries. We examined associations between PM_2.5 components with depression and anxiety among 34,802 Indian adults from the National Mental Health Survey (2015-16). We integrated satellite data and chemical transport modeling at 1-km resolution to assign one-year PM_2.5 component exposures to participants' residential addresses. Mental disorders were assessed using standardized diagnostic interviews. Using logistic mixed-effect regression, we found that an interquartile range increase in PM_2.5 raised the odds of depression and anxiety by 8% (7-9) and 2% (1-3), respectively. Secondary inorganic aerosols and carbonaceous aerosols showed stronger associations than other constituents. The cumulative effect of PM_2.5 components exceeded that of total mass, indicating that relying solely on PM_2.5 mass underestimates mental health effects. Our findings support targeted emission controls that focus on sectors producing the most toxic species, resulting in greater health benefits.