Western Europe is baking. The UK just recorded its highest ever June temperature at 36.1°C, and it felt like 39°C. Thousands of deaths are expected across the continent. But beyond the toll on bodies and infrastructure, researchers are uncovering something less visible: heat waves damage how we think.
It’s not just discomfort. Studies confirm that rising temperatures make people more irritable and more violent. Catherine Thompson, a cognitive psychologist at Liverpool Hope University, has been measuring what happens to firefighters after heat exposure. They struggle to focus. Their attention control drops. The good news? Skills rebound after about 20 minutes of cooling. The bad news? That’s after just 15 minutes of intense heat. Nobody knows what a multi-day heat wave does to cognition — or for how long.
People with mental health conditions are hit hardest. A 2023 review found a 9.7% spike in hospital admissions during heat waves. People with schizophrenia were three times more likely to die during Canada’s 2021 heat dome. Joshua Wortzel, who directs the Heat-Mind Lab at Hartford HealthCare, says the correlation is clear: hotter periods bring worse mental health outcomes.
Young people are especially vulnerable. Wortzel’s recent research found a 2.97% increase in suicide rates among Americans aged 15 to 24 for every 1°C rise in average monthly temperature — more than double the increase seen in older groups. Other work suggests extreme heat during infancy might alter white matter development, with effects detectable years later.
The biological mechanisms remain murky. Animal studies show heat alters serotonin levels and disrupts communication between brain networks. Oxygen delivery to brain cells might be affected too. As Emma Lawrence at Oxford puts it: children born in 2020 will likely experience seven times the heat waves their grandparents did. Adapting to a warming world isn’t optional anymore.
