A unique study design in which rates of depression and anxiety were calculated based on small 5 μg/m3 increases in PM2.5 over different time periods of exposure. In this case PM2.5 could come from many sources including vehicle traffic, indoor cooking, power generation etc. For each 5 μg/m3 increase in PM2.5 for a one week period, there was a 9% higher risk of depression. When the elevated PM2.5 level extended over 30 days, depression rates increased to 20%. Anxiety increased 14% for the one week period and 34% for the 30 day period. Researchers stated in their conclusion that this was "... evidence of positive association between PM2.5 and moderate-to-severe depressive and anxiety symptoms among a representative sample of U.S. older adults. Our findings suggest that people with low SES or with a history of underlying health conditions may be more susceptible to increased odds of mental disorders after PM exposure."
ABSTRACT
Background: Ambient fine particulate matter (PM2.5) is among the most prevalent sources of environmentally induced inflammation and oxidative stress, both of which are implicated in the pathogenesis of most mental disorders. Evidence, however, concerning the impact of PM2.5 on mental health is just emerging.
Objective: We examined the association between PM2.5 and current level of depressive and anxiety symptoms using a nationally representative probability sample (n = 4,008) of older, community-dwelling individuals living across the United States (the National Social Life, Health and Aging project).
Methods: Mental health was evaluated using validated, standardized questionnaires and clinically relevant cases were identified using well-established cutoffs; daily PM2.5 estimates were obtained using spatiotemporal models. We used generalized linear mixed models, adjusting for potential confounders, and explored effect modification.
Results: An increase in PM2.5 was significantly associated with anxiety symptoms, with the largest increase for 180-days moving average (OR = 1.61; 95% CI: 1.35, 1.92) after adjusting for socioeconomic measures (SES); PM2.5 was positively associated with depressive symptoms, and significantly for 30-day moving average (OR = 1.16; 95% CI: 1.05, 1.29) upon SES adjustment. The observed associations were enhanced among individuals who had low SES and history of comorbidity. When considering mental health as chronic conditions, PM2.5 was significantly associated with incident depressive symptoms for all exposure windows examined, but with incident anxiety symptoms only for shorter exposure windows, which may be due to a drop in power resulting from the decreased between-subject variability in chronic PM2.5 exposure.
Conclusion: PM2.5 was associated with depressive and anxiety symptoms, with associations the strongest among individuals with lower SES or among those with certain health-related characteristics.