The mental health toll of heat stress in India

This study assesses the direct, short-term effects of heat stress on mental health and explores potential underlying physiological mechanisms. By using a heat stress measure that accounts for non-linear interactions between heat and relative humidity (wet bulb temperature) and comparing it with conventional temperature measures (dry bulb temperature), I show that neglecting this interaction may underestimate the true effect. I combine data on self-reported depression and anxiety symptoms from four waves of the Indian WHO-SAGE survey with high-resolution climate data, exploiting quasi-random variation in heat exposure driven by the timing and location of survey implementation. The results show that exposure to extreme heat stress (wet bulb temperature) increases the reporting of depressive symptoms, but not of anxiety symptoms. The effects are consistently smaller and insignificant when dry bulb temperature is used together with humidity as a linear control variable. The evidence points to heat stress exposure during agricultural work, increased cognitive difficulties, and sleep disturbances as pathways linking heat stress and mental health among rural populations, while urban populations are not affected. Finally, the study shows that access to the District Mental Health Program plays a protective role, mitigating the negative impact of heat stress on mental health. These results underscore the need to integrate mental health into climate impact assessments and adaptation policies.