How Extreme Heat Affects Our Brain and Mental Wellbeing

As global temperatures continue to climb, extreme heat is becoming an urgent public health threat.

Heat stress is already the leading cause of weather-related deaths and can worsen underlying health issues such as diabetes, cardiovascular disease, asthma, and mental health conditions.

According to the World Health Organisation (WHO), heat-related fatalities are rising sharply, with deaths among people aged 65 and above increasing by 85% between 2000 and 2004 and 2017 and 2021. Older adults, outdoor workers, and individuals in socio-economically vulnerable situations are among the groups most at risk.

How heat affects the brain

Heat not only harms the body, but it also affects the brain. High temperatures can exacerbate neurological conditions such as epilepsy, stroke, migraine, encephalitis, and multiple sclerosis.

For example, people with Dravet Syndrome, a rare form of epilepsy, are susceptible to sudden changes in temperature, which can trigger seizures.

During significant heatwaves, the neurological impacts are clear. In the European heatwave of 2003 and the UK heatwave of 2022, around 7% of additional deaths were directly linked to neurological problems. One international study across 25 countries found that for every 1,000 deaths from ischaemic stroke, the hottest days accounted for two extra deaths.

Our brains are exceptionally heat-sensitive. As one of the body’s most energy-demanding organs, the brain produces heat when it processes information. When external temperatures rise, this can overwhelm the body’s ability to cool itself, impairing normal brain function.

Psychological and cognitive impacts

Extreme heat also affects mood, behaviour, and decision-making. Studies have found that high temperatures can increase irritability, aggression, and depressive symptoms, while also leading to riskier choices.

The American Psychological Association (APA) has warned of wide-ranging psychological impacts, from trouble concentrating to impulsivity. A 2023 APA and ecoAmerica report highlighted that children and young people are especially vulnerable, as heat-related mental health effects may have lasting impacts on developing brains.

Evidence also suggests that extreme heat reduces cognitive performance. An extensive Chinese study found that temperatures above 31.6°C were associated with lower test scores.

Research on firefighters revealed that while simple tasks like arithmetic remain unaffected under heat stress, more complex tasks involving working memory or sustained attention are significantly impaired.

Similarly, a 2022 study reported an 8% rise in emergency department visits for mental health problems on the hottest days compared with the coolest.

Protecting ourselves in extreme heat

So how can we protect our brains and mental health when temperatures soar? Experts recommend practical measures such as:

• Visiting cooling centres or public air-conditioned spaces if home cooling is unavailable.
• Taking cool showers or baths.
• Wearing loose, light-coloured clothing.
• Minimising cooking to keep indoor temperatures lower.
• Staying in shaded areas or wearing a hat outdoors.
• Drinking plenty of fluids.
• Avoiding outdoor activities during peak heat.

These actions, while simple, can help safeguard both body and mind as heatwaves become more frequent and severe.