Ecological associations between depression prevalence and criteria air pollutant concentrations in US adults

The connection between criteria air pollutants and depression has gained increased attention in recent years. Due to this, we explored ecological associations between long-term state means of criteria air pollutant concentrations and prevalence rates of major depressive disorder (MDD) among adults ≥18 years in the US for 2013–2019 from the Mental Health Client-Level Dataset using GEE negative binomial regression adjusted for median age, race, sex, education level, temperature, relative humidity, occupation type, income level, and sunlight. We did not observe significant associations with MDD for any of the four criteria air pollutants examined (PM_2.5, PM₁₀, O₃, and NO₂). However, among the four air pollutants and averaging periods examined, state mean PM_2.5 averaged over 7 years prior to diagnosis was most strongly associated with depression prevalence, and this association approached statistical significance (RR: 1.22, 95% CI: 0.99, 1.49). These findings suggest that future cohort and case–control studies on the criteria of air pollutants and depression should focus on PM_2.5 and evaluate long averaging periods, among other considerations.