Commentary: Extreme heat is making our mental health worse

CHICAGO: Last Monday (Jul 22), planet Earth achieved a terrifying milestone: Global temperatures reached their highest level in recorded history, breaking a record set just one day before. This year is expected to be the hottest in centuries. Heatwaves are hotter, longer and more frequent than they were in the 1960s.

By now, most of us understand that extreme heat is bad for our health, making our hearts, lungs, kidneys and other organs work much harder. But too often we overlook the quieter, less obvious toll heat takes on another vital organ: Our brain.

Extreme heat doesn’t just make us cranky and uncomfortable, it can make it harder to think clearly and be productive at work. It also worsens our mental health, exacerbating common mood disorders like anxiety and depression as well as rarer conditions like schizophrenia and self-harming. With each warming year, that issue deserves more time and attention.

Typically, a part of our brain called the hypothalamus keeps our body at its natural internal temperature (for most, that’s around 37 degrees Celsius). But the human brain only has so much energy to devote to that, explains Kim Meidenbauer, a social, cognitive, and environmental neuroscientist at Washington State University.

On an oppressively hot day, "one of the first things that seems to go is higher cognitive functioning", she says, making it harder to pay attention and impairing working memory (humans’ ability to process and keep track of information in real time).

HIGH COST FOR SOME

For some, that cost is high. The elderly, young children, people taking certain medicines for schizophrenia or depression, and those with certain medical conditions or disabilities have a harder time thermoregulating.

One analysis of commercial health insurance claims over the course of a decade linked hotter days to an increase in emergency room visits associated with a broad array of mental health conditions. 

The rate of ER visits was higher in northern parts of the US, suggesting the need for cities in those areas to better adapt their infrastructure to help people when temperatures soar, says Amruta Nori-Sarma, an assistant professor in the Environmental Health Department at Boston University School of Public Health, who led the work.

Understanding what is driving those visits - and who is at most risk - is critical for preparation and prevention.

Heatwaves have also been linked to a higher risk of suicidality. In its Climate Resilience Review released this month, London officials noted that the risk of suicide is twice as high in the UK when the temperature is 32 degrees Celsius versus 22 degrees Celsius.

And people with schizophrenia are disproportionately at risk of succumbing to the effects of extreme heat. Some 8 per cent of the deaths that occurred during the 2021 heat dome in British Columbia were among people with schizophrenia, a group that comprises less than 1 per cent of the population there.

Liv Yoon, a sociologist at the University of British Columbia, Vancouver, has been trying to diagnose the complex causes of those deaths. Multiple factors are at work, including both physiological deficits and social vulnerabilities, she says.

A symptom of schizophrenia is an unawareness of one’s bodily status - it’s hard to tell how hot or cold you are. Moreover, people with schizophrenia are often taking medication that can compromise the body’s ability to thermoregulate.

WHAT CAN BE DONE?

What’s the solution? Reducing the mental health impact of climate change will require some obvious structural fixes, whether that’s policy aimed at slowing global warming, addressing social determinants of health, or improvements in the design of cities to minimise dangerous hot spots.

Hospitals need to know when to expect an influx of patients, and at the same time, more needs to be done to reduce demand, both by addressing mental health needs before someone reaches the point of a crisis and ensuring people have access to resources amid a heatwave. That’s especially true for people with schizophrenia, who might be less likely to take advantage of public resources like cooling centres.

Many small changes can be made now. For example, training the mental health workforce to be more aware of heat’s dangers could encourage them to check in on the most vulnerable, connect patients with more resources, and make sure they know when their medicines put them at higher risk when temperatures rise.

We all can make a difference, too. “More and more research is finding that social isolation is a huge factor” in predicting someone’s risks amid extreme heat, Yoon says.

The city of Vancouver has been promoting "cool kits", a physical bag of items that can help people stay safe in the heat. But increasingly, she says, public health officials are recognising that social connections matter just as much.

Whether or not someone leans on their community is one of the best predictors of resilience, Nori-Sarma says. “Those social ties are often the most protective measures we have in place.”

Checking in on friends, tuning into the family text chain, keeping an eye out for your neighbours that live alone - those small acts can have a big impact on our most vulnerable members of society.

As this scorching hot summer drags on, that’s worth remembering.