As the US recovers from its 4 July heatwave, a new study in Nature Health warns of an impending uptick in people attending hospitals for mental health and behavioural disorders, according to the first multi-country study of heatwave-related mental health hospitalization, led by Monash University in Australia.
The study, led by Professors Yuming Guo and Shanshan Li and published in Nature Health, looked at more than 2.6 million warm-season hospitalisations from 852 locations in Brazil, Canada, Chile and New Zealand from 2000 to 2019 – finding that sustained exposure to extreme heat, as experienced in heatwaves, was associated with an increased risk of hospitalization for mental and behavioural disorders.
A heatwave is defined as a period of extremely high ambient temperatures that lasts for several days, during which heat-related disease and death rise substantially.
According to Professor Guo, the association between exposure to a heatwave and hospitalisation for mental and behavioral disorders was more pronounced among older adults and residents of low-population-density areas. “These findings indicate that prolonged extreme heat can acutely increase mental health-related hospital demand and support targeted preparedness during severe heatwaves,” he said.
Professor Li added that climate change “has emerged as a pressing factor influencing mental health on a global scale, with extreme weather events, resource scarcity and ecosystem disruptions amplifying psychological stress and mental health risks.”
“And one noticeable climate-related issue is the increasing frequency and intensity of heatwaves, such as those being experienced in the US and across Europe at the moment,” she said.
Heatwaves may trigger acute exacerbations of mental and behavioural disorders through sleep disruption and physiological stress responses, with heightened vulnerability among individuals with impaired thermoregulation or medication-related heat sensitivity.
Heat-related psychological distress and behavioural changes during heatwaves may further contribute to symptom destabilization and increased hospital admissions.
This study is the first to estimate heatwave-related hospitalization risks and burdens for mental and behavioral disorders across different countries, sexes, ages, GDP per capita, population densities, air-conditioner penetrations, travel time to healthcare facilities and causes of mental health and behavioral disorders.
Nature Health
Meta-analysis
People
Mental health hospitalizations associated with sustained extreme heat in multiple countries
10-Jul-2026