Long-term exposure to air pollutants, meteorological factors, and mental health status: a nationwide population-based study with multilevel regression analysis

Background: Air pollutants and meteorological conditions have shown significant adverse effects on human health; however, their impact on mental health remains inconclusive and underexplored. Thus, this study aimed to investigate the association between long-term exposure to air pollutants (PM_2.5 and PM₁₀), meteorological factors, and depression and anxiety. 

Methods: We selected 10,076 participants aged 15–49 from the Nepal Demographic and Health Survey (NDHS) 2022, who had lived in their current domiciles for over five years. The Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder (GAD-7) scale were used to quantify the presence of depression and anxiety. The mean levels of air pollutants (PM_2.5 and PM₁₀), temperature, and relative humidity between August 2021 and July 2022 were obtained from the national air quality monitoring center and the meteorological department. Adjusted linear and polynomial logistic regression models were used to estimate the risk of depression and anxiety. 

Results: The prevalence of depression and anxiety among participants was 3.8% and 16.9%, respectively. Increased PM_2.5 and PM₁₀ concentrations were significantly associated with increased PHQ-9 (PM_2.5: β, 0.015; PM₁₀: β, 0.011) and GAD-7 (PM_2.5: β, 0.024; PM₁₀: β, 0.011) scores. Exposure to higher PM_2.5 and PM₁₀ concentrations increased the risk of depression {OR, 95% CI (PM_2.5: 1.05, 1.03–1.08); (PM₁₀: 1.04, 1.01–1.05)} and anxiety {OR, 95% CI (PM_2.5: 1.06, 1.04–1.10); (PM₁₀: 1.03, 1.01–1.04)}, whereas higher temperatures and higher humidity showed a protective effect (p < 0.05). 

Conclusion: This study demonstrates the substantial impact of air pollutants and meteorological factors on mental health status. Findings suggest that exposure to air pollutants may serve as an independent risk factor for depression and anxiety. Therefore, further robust investigations including large epidemiological cohorts and longitudinal observational studies are needed to elucidate these associations. Clinical trial number: Not applicable.