Extreme heat events have long been recognised to negatively affect physical health, exacerbating cardiovascular and respiratory disease and increasing the risk of death.3 More recently, we have begun to understand the impact that extreme heat can have on our mental health. Links have been found between higher ambient temperatures and increased hospital attendance for mental health problems, as well as greater incidence of suicide.4,5
Cities and other urban areas have a dual risk to contend with. Urban living is already associated with a higher prevalence of mental health conditions than in rural areas.6 Additionally, cities and towns are affected by the heat island effect,7 whereby the mix of higher heat output, heat-absorbent surfaces, and low levels of vegetation lead to higher temperatures. This combination makes urban populations particularly vulnerable to the mental health impacts of extreme heat. However, few studies have explored these impacts specifically in urban communities.8,9
This is why we have launched the Extreme Heat and Mental Health project, a multidisciplinary collaboration aiming to quantify the impacts of extreme heat on mental health in vulnerable urban populations.10 By bringing together datasets on mental wellbeing and mental health service use, and high-resolution spatiotemporal datasets of environmental characteristics, we hope to elucidate not just the impact of extreme heat on mental health in London, but also which environmental factors may exacerbate or lessen these impacts.
Preliminary findings from our project suggest that elevated temperatures are associated with increased mental health service use among people with existing mental health conditions. For example, we have found an increased risk of inpatient admissions as temperatures rise above 30°C, compared with ambient temperatures of 18°C. Importantly, while present for people with any mental health condition, we have found more elevated risks among those with mood or affective disorders, meaning that some groups may be more affected by extreme heat than others. Our initial analyses also suggest that the association we are seeing between extreme heat and mental health service use may be affected by levels of green space exposure—such as trees, parks, and gardens—with a reduction in risk in areas with a higher density of green space. In other words, a greater quantity of parks, gardens, and trees in someone’s neighbourhood may reduce the effect of extreme heat on their mental health.
There is much more we plan to explore within this project, but these initial findings raise some important questions. If we are seeing these associations now, how will urban communities and their mental health be affected as temperatures continue to rise? What measures can be put in place to protect vulnerable communities and mitigate the effects of extreme heat on their mental health?
A key step may be to reconsider the very fabric of our urban settings. Green space supports mental wellbeing and reduces incidence of mental health disorders.11 It reduces ambient temperatures, provides opportunities for shade, and lessens the impacts of heatwaves.12 And our findings, like other studies,13 suggest that green space may be fundamental in protecting urban mental health from the impacts of extreme heat events. Protecting, enhancing, and developing green spaces within cities and towns may be a necessary step to supporting urban mental health in a changing climate.
(*) https://www.metoffice.gov.uk/about-us/news-and-media/media-centre/weather-and-climate-news/2025/summer-2025-is-the-warmest-on-record-for-the-uk
References
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10. Chukwusa E, Vivaldi G, Baecker L, et al. A longitudinal, population-based, record-linked natural experiment on the effects of extreme heat events on mental health in urban communities: a study protocol. BMJ Open 2025; 15(10): e099771.
11. Geary RS, Thompson D, Mizen A, et al. Ambient greenness, access to local green spaces, and subsequent mental health: a 10-year longitudinal dynamic panel study of 2·3 million adults in Wales. The Lancet Planetary Health 2023; 7(10): e809-e18.
12. Huang H, Lu Z, Fan X, et al. Urban heatwave, green spaces, and mental health: A review based on environmental health risk assessment framework. Sci Total Environ 2024: 174816.
13. Lavigne E, Maltby A, Côté J-N, et al. The effect modification of extreme temperatures on mental and behavior disorders by environmental factors and individual-level characteristics in Canada. Environmental Research 2023; 219: 114999.