Study Links Temperature and Humidity Extremes to Mental Health Risks

Mental disorders (MDs) constitute a major cause of global disease burden, critically impairing cognition, mood, and social behavior. Extreme heat and humidity are emerging as significant drivers of MDs, exacerbating heat stress and its related effects on mental health. Current literature lacks a comprehensive assessment of the joint influence of temperature and humidity extremes on MD incidence, necessitating targeted investigations.

In this study, we analyzed individual-level emergency medical service (EMS) calls related to MDs in Shenzhen, focusing on two temperature-humidity indices: humidex and heat index. The study, employing a conditional logistic model within a time-stratified case-crossover framework, aimed to explore nonlinear correlations between these indices and MDs-related EMS calls, investigate delayed effects, and define high-risk thresholds for MDs in response to extreme temperature-humidity scenarios.

From October 1, 2011, to June 30, 2023, a total of 33,568 MD-related EMS calls were recorded from a broader dataset of 1,538,611 EMS calls. Analysis demonstrated a significant correlation (OR = 1.10, 95% CI: 1.05–1.15) between high extremes of humidex and heat index and increased MD-related EMS calls, particularly following lags of one day. Notably, younger individuals (aged ≤ 34 years) and females exhibited heightened sensitivities under extreme conditions, with risk patterns peaking during warm months.

This research underscores the urgent need for effective public health strategies aimed at addressing the mental health risks associated with extreme temperature and humidity conditions. The findings suggest that local health authorities should enhance early warning systems for at-risk populations and develop preventive measures to mitigate the impact of climate extremes on mental health. Limitations include a focus solely on acute MD outcomes, which restricts broader generalizability, and the need for multicenter studies to validate results across diverse climates.

Original citation address: https://www.besjournal.com/en/article/doi/10.3967/bes2025.150