Higher temperatures are associated with the increase in suicidal thoughts and behaviors

Researchers have linked higher temperatures to an increase in suicidal thoughts and behavior in young people. The new study adds to existing evidence that rising temperatures also affect the mental health of adult men and women.

There are a number of known risk factors associated with suicidality and suicide among young people: a recent or serious loss, such as the death of a parent; stressful life events such as bullying; psychiatric illness, especially a mood disorder such as depression; trauma; and substance abuse problems.

However, new research led by the University of New South Wales (UNSW) Sydney has added another risk factor. A link was found between an increase in suicidal thoughts and behaviors in young people and higher temperatures.

The researchers examined 55,000 emergency department (ED) presentations about suicidality by people aged 12 to 24 in New South Wales state during Australia’s warmer months (November to March) between 2012 and 2019.

When they compared this data with daily mean temperature (DMT) and heat waves, they found that suicide rates among young people were significantly higher on warmer days. The relationship was linear: for every 1°C (1.8°F) increase in DMT, youth emergency room visits due to suicidal thoughts or behavior increased by 1.3%.

“The impact on the very first day when temperatures are higher than normal is as bad as any subsequent day, and the effect begins at a more moderate temperature than expected,” said Dr Cybele Dey, a psychiatrist and lecturer at UNSW Sydney and the leader of the study and the corresponding author.

For example, on days with a 24-hour average temperature of 21.9°C (71.4°F), which was the average DMT for the study period, there were an average of 45.7 suicidality presentations among youth across the state. At that temperature, presentations were 4.7% higher than would normally have been the case at the state’s spring average DMT of a cooler 18.3 °C (64.9 °F).

When the DMT rose to 25.2 °C (77.4 °F), which is the baseline for a heat wave, presentations were about 9% higher than during the spring DMT. By the time the DMT reached the ‘extreme heat’ temperature of 30°C (86°F), presentations were approximately 15% higher.

“There was an increase in the number of presentations on the first moderately warm day, which tells us it is more likely a biological effect, rather than a consequence of factors such as poor sleep,” Dey said. “The heat itself seems to do something to increase people’s suffering and that is supported by other literature. We know that calls for mental health crises increase as temperatures rise, and there are studies overseas showing a link between heat exposure and suicidality, as well as higher temperatures and deaths from suicide.”

In August 2024Research led by Curtin University found that over a period of almost two decades, about 0.5% of suicide deaths in Australia – 264 people – correlated with unusually higher temperatures due to climate change. Suicides associated with heat abnormalities were statistically significant among men aged 55 years and older. Seasonality was an important factor, with more deaths in spring (September to late November) and summer (December to late February).

A few months earlier, inside AprilResearch led by the University of Sydney had found a link between higher temperatures and psychological distress at a Sydney hospital, particularly in women, for whom the risk increased significantly at temperatures of 29.2°C (84.6°F) or higher.

The researchers in the current study said that socio-economic disadvantages associated with lower quality housing and the ownership and use of air conditioners were a relevant consideration, as well as more limited access to green spaces and waterways.

“Independent access to green space, night-time cooling from sea breezes and the quality of your housing are all important factors in determining how people cope with heat,” says Dr Iain Perkes, psychiatrist and senior lecturer at UNSW’s School of Clinical Medicine and the co-corresponding author. “We will need to do more research into these possible mediating factors, but that shouldn’t stop us from moving forward and making sensible changes that we know work more broadly to reduce exposure to higher temperatures.”

They said better housing quality and giving young people access to cool environments at home and at school could better protect them from the mental health effects of higher temperatures.

“Public health messages about heat are usually limited to heat waves and are aimed at the very young and the elderly,” says Dey. “But we must do more to warn and protect the entire population from the impact on both their physical and mental health.”

Doctors for the Environment Australia (DEA), a group of doctors calling for climate action to reduce damage to health, has called for the urgent phase-out of fossil fuels based on the study’s findings.

“Our research shows that the mental health of young Australians is suffering in the heat, and we know that climate pollution is contributing to the increase in extreme weather events, including heat,” said DEA spokesman James Scott, professor of child and adolescent psychiatry and professor child and adolescent psychiatry. co-author of the study. “To reduce heat-related damage to the mental health of children and young people and reduce the number of ED presentations, we need an urgent and rapid transition from fossil fuels to clean energy.”

Further research is needed into the link between young people’s mental health and heat to confirm whether higher temperatures are driving the increase or simply coinciding with it.

“It’s pretty staggering,” Perkes said. “Although we have not established causality here, the type of pattern … would indicate a cause-and-effect response.”

The research was published in the Australia and New Zealand Journal of Psychiatry.

Sources: UNSW Sydney, D.E.A