Extreme Heat and Mental Health: From Global Evidence to Local Action in Geneva, Switzerland

Climate change is accelerating the frequency and intensity of extreme heat events worldwide, with heatwaves projected to increase globally and hot day-and-night episodes in Geneva expected to more than double from 48 to 108 per decade by 2050 under the RCP8.5 scenario. Mortality, especially induced by cardiovascular and respiratory-related conditions, is the most studied health outcome related to heatwaves. It has been estimated that by the 2080s, heat-related mortality in Europe could cause between 50,000 and 160,000 additional deaths each year. Beyond their mortality and physical health toll, heatwaves have profound and under-recognised effects on mental health. People with pre-existing psychiatric disorders face substantially higher mortality during heatwaves than the general population, a vulnerability compounded by many psychotropic medications that can impair thermoregulation. These intersecting risks converge in Geneva, where Switzerland’s largest public hospital Geneva University Hospitals (HUG) is developing innovative climate-adaptive healthcare through the Ecological Transition in Healthcare (TES) programme. This perspective piece integrates global evidence with Swiss findings to argue that the mental health impacts of extreme heat are neither abstract nor distant: they are measurable, unequally distributed, and urgently in need of context-specific research and institutional response. We call for the systematic evaluation of heat-health clinical interventions that could inform more targeted climate-adaptive care.