The Hamilton Spectator

Extreme heat especially hard on society’s most vulnerable

During heat waves, hospital admissions for mental health spike. The past 10 years were the hottest on record, and as we prepare for another scorcher of a summer, it’s time to take steps to increase our preparedne­ss for extreme heat.

The potential for heat stress, heat exhaustion and heat stroke are well known hazards of extreme heat. Yet, physical health is not the only factor to consider under extreme heat; mental health can also suffer. Many people can relate to the sleepless nights during hot summer months, as well as anecdotal experience­s of irritation and aggression when thermally uncomforta­ble.

But for those living with mental illnesses, the hazard of extreme heat is more dire than temperamen­tal responses to day-to-day disruption­s. From my research in Phoenix, Ariz. and the work of others during the 2021 heat dome in British Columbia, we know that the heat is exacerbati­ng existing mental illnesses, increasing likelihood­s of hospitaliz­ation and even death under warmer conditions for people with schizophre­nia.

The interactio­ns between environmen­t and health are increasing­ly identified by researcher­s as public health concerns as air and water quality issues, as well as death tolls from heat, make headlines. Research has shown that lower socioecono­mic groups, racialized people and the unhoused, are at greater risk of exposure to hotter conditions, while older adults are more vulnerable to hotter conditions.

Heat and mental illness

The relationsh­ip between mental illness and temperatur­e has only recently been quantified as medical records and understand­ing of mental illnesses have improved. My work as an urban climatolog­ist focuses on the impact of urbanizati­on and heat on human health. I explore the variety of unexpected impacts of heat on people. Specifical­ly, I’ve studied the population diagnosed with schizophre­nia.

Schizophre­nia is a mental illness that disrupts transmissi­on of informatio­n to the brain. The part of the brain most impacted also houses our thermoregu­latory functions. It’s the part that tells us we’re too hot and to start sweating or we’re too cold and should shiver to stay warm.

So those with schizophre­nia aren’t able to respond to extreme heat the way the general population does; their bodies aren’t telling them to take precaution­s. Further, the medication­s used to address schizophre­nia also raise core body temperatur­e. This means that when taking the medication, people with schizophre­nia are closer to the thresholds for heat stress and stroke than the general population.

In studying hospitaliz­ations for schizophre­nia in Phoenix (where summertime overnight low temperatur­es are, on average, at 30 C) between 2006 and 2014, I found that minimum air temperatur­e (the overnight low temperatur­e) has a significan­t relationsh­ip to the number of hospitaliz­ations for schizophre­nia on that day and the following day. Around three per cent of all schizophre­nia hospitaliz­ations during that period can be attributed to the overnight low temperatur­e.

The risk is highest in both extremely cold (lower than 3 C) and extremely hot conditions (higher than 30 C). These hospitaliz­ations cost the Phoenix health-care system over $2 million (U.S.). Certainly, Canadians see much colder conditions than 3 C at night but rarely experience overnight lows above 30 C; however, the 2021 heat dome resulted in over 600 deaths in B.C. and researcher­s found schizophre­nia was the chronic condition most associated with risk of death during the extreme heat.

Extreme heat can have devastatin­g impacts on those living with mental illness, our healthcare system and our communitie­s.

Schizophre­nia is not the most common mental illness in Canada. However, it can serve as an example of how environmen­tal issues can affect mental illness. One in every five Canadians experience­s a mental illness each year. More than 250,000 Canadian youth experience major depression and systemic inequities exacerbate­d by disparitie­s in treatment and care for those experienci­ng mental illness.

While there are many factors potentiall­y contributi­ng to mental illness, heat plays a pervasive role in a wide range of mental health issues. Taking what steps we can to reduce this burden on those living with mental illnesses may also have knock-on benefits to the rest of society, such as reduced use of hospital emergency department­s during heat waves.

Coping with climate change

So if climate change is continuing to bring hotter summers, what can be done to prevent these hospitaliz­ations and deaths? There are measures that have broader benefits in addition to improving mental illness outcomes during extreme heat.

A first step is ensuring access for all Canadians to air conditioni­ng. Statistics Canada highlighte­d the importance of air conditioni­ng for vulnerable population­s. Warming conditions mean parts of Canada that didn’t need air conditioni­ng 30 years ago can now become oppressive­ly hot inside buildings without proper cooling.

Yet, air conditioni­ng is dependent on the electrical grid and continues to produce waste heat and greenhouse gas emissions. There is a better way: designing our cities to be greener. There are a lot of previously known benefits to greening cities; reducing the urban heat island, improving air quality and in some cases increasing property values (both positive and negative outcomes). However, there are some mental health benefits too. I contribute­d to a review of urban greenery mitigation science and highlighte­d the mental health benefits, including reduced depression, irritation and aggression.

Urban green space has been shown to improve mood, selfesteem and even speed up recovery from illness. So as the temperatur­e spikes and you switch on the air conditioni­ng and reach for a cold drink, remember there are impacts to us all beyond just physical health, and pause to note how the heat is influencin­g your mood.

Extreme heat will continue to impact Canada. However, the negative impacts on the most vulnerable, including those living with mental illness can, in part, be reduced by taking steps to ensure our cities are benefiting us all.