BACKGROUND: Depression and anxiety have complex etiologies and are associated with a significant burden of disease. Although air pollution has been hypothesized as a possible risk factor of these disorders, the associations are still under-investigated. We aimed to analyze associations between long-term exposure to ambient ozone and particulate matter with diameter <10 μm (PM 10) and diagnoses of depression and anxiety in a general population.

METHODS: We utilized data from a large statutory health insurance company from Saxony, Germany. Information on outpatient clinical diagnoses of depression and anxiety was available for the years 2005-2014. We assigned ambient ozone and PM 10 estimates to residential districts of 1.13 million individuals aged 16 and older. Depression and anxiety were defined as diagnoses counts. Associations with depression and anxiety were assessed using adjusted generalized estimating equations models.

RESULTS: In the ten-year study period, the observed prevalences of depression and anxiety were 7.40% and 3.82%, respectively. In the two-pollutant model, 10 more days with a maximum 8-h average ozone concentration exceeding 120 μg/m³ resulted in a relative risk (RR) of 1.010 with 95% confidence interval (CI) (1.005, 1.014) for depression and an RR of 1.007 (95% CI (1.000, 1.014)) for anxiety. The effect estimates of PM 10 for depression and anxiety were 1.180 (95% CI (1.160, 1.201)) and 1.176 (95% CI (1.148, 1.205)) per 10 μg/m³ increase in PM 10 concentration, respectively. Age, sex, and access to healthcare of the individual were also associated with the diagnosis of the disorders. The associations were consistent across one- and two-pollutant models.

CONCLUSIONS: Our findings indicate that increased levels of ambient ozone and PM 10 may elevate the risk of a depression or anxiety diagnosis in the general population. However, given the lack of data on individual air pollutant exposure and socioeconomic status, our results should be interpreted with caution. Further well-designed epidemiological studies should replicate our findings.