Fig. 2

Associations between long-term air pollution exposure (per 10 \(\mathrm{\mu g}/{m}^{3}\) increment) and depression. The square symbol represents odds ratio and the horizontal line represents 95% confidence interval. The odds ratio was estimated from the generalized estimating equation (GEE) model, and depression was defined as having a CES-D 10 score of 20 points or over. The models were adjusted for baseline depression status, sex, age group, current smoking, current drinking, education attainment, marital status, social contact, self-reported health status, exercise, private medical insurance, longitude, latitude, and the interaction term of longitude and latitude, population density, the number of beds in hospitals per 1,000 persons, the number of national basic livelihood beneficiaries, the independent rate of finance of local government, and the proportion of basic pension beneficiaries except for the subgroup variable itself in the model. The p-values for interactions were calculated from models that included interaction terms for each subgroup and air pollution. PM_2.5: particulate matter with an aerodynamic diameter ≤ 2.5 μm; PM₁₀: particulate matter with an aerodynamic diameter ≤ 10 μm