Remote Sensing of Mental Health: The Burden of Heat Exposure in Switzerland. An Interdisciplinary Study Combining Earth Observation and Epidemiology.

Climate change is intensifying summertime heat exposure across Europe, with growing implications not only for physical human health but also for population mental well-being. However, heat-health research has focused mainly on the physical outcomes of heat exposure; mental health impacts remain underexplored. In particular, spatially and temporally explicit analyses that capture variation in heat exposure across diverse regions are scarce, limiting the systematic identification and monitoring of vulnerable populations. Switzerland serves as a suitable case study for addressing this gap, given its pronounced warming trends and environmental heterogeneity, while the underlying analytical approach is transferable to other countries and regions.

This study investigates the relationship between heat and mental health outcomes in Switzerland by integrating population health survey data with satellite data-based heat metrics in a spatially and temporally explicit framework. The study is grounded in a heat-mental health risk framework linking thermal hazard, spatiotemporal exposure, and demographic vulnerability. Individual-level mental health data from the Swiss Health Survey (a comprehensive national health survey conducted in 2007, 2012, 2017, and 2022) are combined with high-resolution land surface temperature (LST) derived from MODIS Aqua as the primary heat exposure indicator, alongside gridded near-surface air temperature for comparison and benchmarking. The temperature metrics are designed to represent environmental heat load rather than single-day extremes. Mental health is expressed through multiple standardised indices capturing psychological burden, vitality, depressive symptoms, and anxiety. To account for spatiotemporal dependencies, we apply hierarchical Bayesian ordinal regression models that also serve as predictive models for scenario-analysis.

Results indicate that higher LST is generally associated with poorer mental health outcomes across Switzerland, with the strongest and most credible associations observed during the exceptionally hot summer of 2022. We also found that LST-based models outperform air-temperature-based models, which indicates the added value of thermal remote sensing in heat-health studies across spatially heterogenous areas. Spatial analyses reveal pronounced regional and urban-rural gradients in both heat exposure and baseline mental health, while demographic factors such as age and biological sex exhibit substantial variation in mental health vulnerability but do not significantly modify the heat-mental health relationship itself.

By integrating remote sensing, climatological data, and population health records, this study demonstrates a scalable interdisciplinary approach for assessing climate-sensitive mental health risks across space and time. It provides a foundation for integrating mental health into climate adaption, heat warning systems, and spatially targeted public health planning.