Heatwaves continue to intensify across the globe. According to the World Health Organisation, heat is an important environmental and occupational health hazard and is the leading cause of weather-related deaths. Excessive heat can stress the body and increase the risk of accidents and transmission of some infectious diseases. Intense heatwaves are known to cause heat-related illnesses, including heat cramps, heat rash, heat exhaustion and heat stroke.

These conditions occur when the body gains heat faster than it can cool itself down. Under normal conditions, the brain's hypothalamus regulates temperature by triggering sweating and dilating blood vessels to release heat through the skin. However, in extreme heat, high humidity, or during intense physical exertion, these cooling mechanisms can fail, leading to dangerous spikes in core body temperature.

A recent study published in the journal Nature Health, led by researchers at Monash University in Australia, has highlighted how long periods of extreme heat impact the mind.

The researchers conducted a massive, multi-country study. They analysed a dataset of over 2.6 million hospital admissions during the warmer months across 852 different locations in four countries: Brazil, Canada, Chile, and New Zealand, between 2000 and 2019. They looked at how spikes in prolonged, extreme heat matched up with people being admitted to the hospital for mental health and behavioural disorders.

Major findings

  • Extreme heat drives mental health crises

The study found a clear, undeniable link between sustained extreme heat and a sudden surge in hospitalisations for mental and behavioural disorders.

  • Older adults are at higher risk

The connection was much more severe in older populations. As you age, your body is less efficient at regulating temperature, making the elderly physically and mentally more vulnerable to the stress of a heatwave.

  • Rural and isolated areas suffer more

People living in areas with lower population density, like rural or less crowded towns, saw a more pronounced increase in heat-related mental health hospitalisations, likely due to fewer immediate resources or longer travel times to hospitals.

  • Climate change amplifies the threat

The researchers emphasise that climate change is actively increasing the frequency and intensity of these heatwaves. This makes extreme heat a growing, global threat to psychological well-being.

Why does this happen?

The researchers highlighted a few main biological and environmental reasons why hot weather destabilises mental health:

  • Sleep disruption

Extreme heat makes it incredibly hard to sleep properly. A few nights of severe insomnia can quickly destabilise one's mental health.

  • Physical stress responses

The body has to work overtime to stay cool. This physiological strain triggers stress hormones and inflammation, which can aggravate underlying psychiatric conditions.

  • Medications and temperature regulation

Many people with pre-existing mental health conditions take medications that interfere with the body's natural ability to regulate its own temperature, making them highly sensitive to overheating.

The study concludes that heatwaves aren't just dangerous for your physical health, causing heatstroke or dehydration, they severely strain your mind. The researchers urge public health sectors to use this data to proactively prepare mental health services and protect vulnerable groups, such as the elderly and rural residents, before a severe heatwave strikes.



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