Individual and combined effects of heatwaves, air pollution, green spaces, and blue spaces on depressive symptoms incidence

The health hazards of climate-driven temperature have been extensively studied, but the specific effects on mental health, especially given the backdrop of air pollution and blue-green accessibility, remain largely unknown. Here we investigate individual and synergistic effects of heatwave, air pollution, and blue-green space on depressive symptoms, using data from the China Health and Retirement Longitudinal Study (CHARLS). Logistic regression analyses revealed that exposure to heatwaves was associated with a 4.2–14.0 % increase in depression risk. Furthermore, for every 10 μg/m³ increment in ambient concentrations of PM_2.5, PM₁₀, CO, and SO₂, the odds ratios (ORs) of depression increased by 25 %, 13 %, 1 %, and 55 %, respectively. We also found positive interactions between the concentrations of PM_2.5, PM₁₀, SO₂, CO, and the lack of blue and green spaces with heatwave exposure, both on multiplicative (ORs for product terms >1) and additive (RERIs >0) scales. Simultaneous exposure to heatwave and air pollution or lack of green and blue spaces showed increased risk of depression symptom than exposure alone. This study advocates integrating heatwaves, air pollution, and blue/green infrastructure into climate-resilient mental health policy-making.