Extreme high temperatures double young people’s risk of mental health admissions, Australian research shows

Exclusive University of Sydney study finds heat-related hospital admissions to increase by 6% to 7.7% by the end of the century

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Extreme high temperatures in warmer months double the risk of young people being admitted to hospital for a mental health condition, according to research.

The analysis, which looked at 720,000 New South Wales hospital admissions of young people aged up to 24, suggested the climate crisis would aggravate the already declining mental health of young people.

As extreme temperatures occur more often because of global heating, heat-related hospital admissions would increase between 6% and 7.7% by the end of the century, the research said.

The lead author of the research at the University of Sydney , Dr Wen‑Qiang He, said: “We found that as temperatures increase, we see admissions for these younger populations increase significantly. The risk doubles in the warm season and triples in the cold season.

“That’s important for us to know and if we can let the community know what’s happening, then we can prepare and help our children and young people.”

The research, published in the Journal of the American Academy of Child and Adolescent Psychiatry , examined the 720,000 times between 2001 and 2022 that young people aged up to 24 had to be admitted to hospital for a range of mental health conditions.

The serious hospital admissions – meaning they were admitted to the hospital rather than just visited an emergency department – included categories of mental health disorders such as schizophrenia, depression, substance misuse, eating disorders and self-harm.

Researchers found when daily average temperatures were in the highest 1% for that day, the risk of a hospital admission was doubled in warmer months from October to March and tripled during the cooler months.

Previous research has found that young people in NSW present to hospital with suicidal thoughts and behaviours more often on days that are hotter than average.

The National Climate Risk Assessment, released last year, warned that extreme heat had been linked to “higher rates of suicide and mental health-related hospital admissions” with research pointing to “heightened stress, anxiety, and aggravation of psychiatric conditions”.

The new research did not try to discover why the higher temperatures were correlated with an increase in mental health hospital admissions, but the authors said there were several possible causes.

In warmer months when absolute temperatures are higher, there was evidence from other studies that this could directly affect brain function, having knock-on effects for mental health.

Unexpected temperature changes, such as those experienced in winter, could also affect the way people deal with stress, and alter sleep and mood.

Dr Cybele Dey, an adolescent psychiatrist in Sydney and co-author of the research, said the data showed there was little lag between the temperature spikes and the hospital admissions, which suggested the heat was causing a “physiological” response.

“These are not mild presentations. There has to be a lot going wrong for a person to be admitted,” she said.

“Climate change is already impacting children and young people’s mental health in multiple ways. This is not the first study to show a link between unusually warm temperatures and children being admitted to hospital with mental disorders.”

Dr Hasini Gunasiri, a research fellow at the not-for-profit Melbourne-based youth mental health research institute Orygen, said the findings had “important practical implications” in caring for young people.

Gunasiri, who was not involved in the research, said during periods of extreme heat, young people might use alcohol or other substances to cope with discomfort, irritability, sleep disruption or emotional distress.

Heat can also increase impulsivity and risk-taking behaviours, she said, as well as behaviours that can increase thoughts of self-harm.

“Sleep disruption may be especially relevant here. Poor sleep is a well-established risk factor for suicidal ideation and self-harm in young people,” she said.

“Current heat-health policies tend to focus on physical health outcomes such as heatstroke, dehydration and cardiovascular illness, particularly among older adults.

“These findings suggest that mental health should also be considered when planning for extreme temperatures, especially for children and young people.”

She said the health system could incorporate mental health messaging into heat warnings to increase awareness among clinicians and families of the potential mental health impacts of heat.