People with schizophrenia are the unseen victims of heat waves 

On 25 June, 2021, a wave of extreme heat descended across the Pacific Northwest. Health officials in British Columbia issued government guidance calling on residents to seek shelter in cool places, avoid exercising outdoors, and to look after the vulnerable – particularly the elderly and children. The heat dome raged for a week, and by the time it was over the region broke the highest temperatures on record. In Lytton, British Columbia temperatures smashed 49 °C.  

Despite issuing health warnings, the province’s coroner said there was an excess of 619 deaths over the course of the week. Not all of these deaths were spread evenly throughout society. Although people with schizophrenia make up less than 1% of the population, they accounted for almost 16% of deaths during the heatwave. During a similar heat event in Montreal in 2018, schizophrenics made up 26% of excess deaths. One study looking at 8,000 excess deaths from heat waves revealed that people with schizophrenia were three times more likely to die during a heat wave than during a normal summer.   

There are several reasons why mental illness, and schizophrenia in particular, is exceptionally deadly during a heat wave. For one, schizophrenia is associated with a disorder called anosognosia which causes a lack of insight into a person’s biological condition. Temperatures could be sweltering, but somebody with this disorder could still put on a jacket and walk around in the middle of the day.

Another reason is that antipsychotic and antidepressive medications can interfere with the body’s ability to thermoregulate, alter perception, and compromise the ability to sense and respond to heat. Added to all that is the stigma associated with schizophrenia that makes it difficult for many people living with the mental illness to be present in public spaces.  

Far too few cities have heat adaption plans and public health measures for heat waves, but even those that do, often lack specific guidelines for people living with severe mental illness. Most plans ask residents to make daily checks on loved ones during peak daylight hours, but those with mental illness are more likely than the general population to live in isolation without close ties.  

A common feature of adaption plans is public cooling stations such as libraries or shopping malls where residents can have access to air conditioning. British Columbia had designated cooling stations during the heat wave of 2021, but many people with mental illness were unable to access them, either because they were unaware of them, or because they didn’t have access to public transport.  

One of the biggest challenges for those with mental illness during heat waves is the secondary effect of substance abuse. A study from 2025 that explored the vulnerabilities of people with schizophrenia during the British Columbian heat wave found that 92% of participants reported actively using substances during the heat dome. Drug and alcohol use exacerbated their schizophrenia symptoms, and also contributed to a heightened sense overheating as well as increased heart rate. Others reported that isolation and boredom from stay-at-home orders made them more likely to abuse drugs.  

There is no single silver bullet solution that will prevent all excess deaths for those living with severe mental illness. Cities should instead focus on systems change that target the particular vulnerabilities of schizophrenia. This includes everything from establishing individualised care plans to retrofitting social housing with air conditioning. Hospitals should have plans in place for the sudden intake of psychiatric patients during heat waves. 

A handful of cities have taken the extra step to include care for the mentally ill in their heat adaptation plans. In Athens, psychologists are deployed during heat waves to visit the elderly and other vulnerable individuals. Montreal’s heat response plan has been revised to include people with mental illness as a vulnerable subgroup of the population. The London borough of Southwark has a specialised heat preparedness plan that focuses specifically on people with mental health problems. Pilot programmes are under way to train medical professionals about the risks of heat and mental health, and social workers are targeting patients to understand how they can be better supported during an extreme health event.  

People with schizophrenia are already among the most vulnerable members of society, facing higher rates of isolation, poverty, poor physical health and premature mortality than the general population. Extreme heat does not create these vulnerabilities, but it magnifies them, often with deadly consequences. As heat waves become more frequent and intense, cities must recognise severe mental illness as a major public health risk factor and plan accordingly. The same attention given to protecting the elderly and other at-risk groups during extreme heat should be extended to people with schizophrenia, whose lives are too often overlooked in climate adaptation strategies. 

On 22 June, in partnership with Wellcome, we will host our ‘Climate and the Future of Health’ summit to explore how extreme heat is impacting the health of workers and national and local infrastructures. We hope to see you there.