Extreme heat leads to worse mental health for young people  

A new study by researchers from the University of New South Wales, of 55 000 youth presentations to emergency departments with suicidal thoughts and behaviours demonstrates a clear link with hot weather.

Youth emergency presentations with suicidal thoughts and behaviour have increased in Australia, and globally over the past 10–15 years and these rises are not accounted for by known risk factors such as bullying, mental illness or the disruptions linked to the COVID-19 pandemic. Over the same time period, exposure to hotter weather has also increased, leading us to investigate a possible link between hot weather and youth emergency presentations with suicidal thoughts and behaviour. Our suspicions were confirmed. 

Our study found that for every 1°C rise above average daily mean temperature, youth suicidality presentations to NSW emergency departments increased by 1.3%. These findings relate to young people being physically too hot, not to their emotional response to or understanding of the scientific reality of climate change.

Initially, colleagues were sceptical that heat and youth suicidality could be connected, but it fits with international evidence showing that a wide range of child and youth mental health emergency presentations are also linked to higher ambient temperatures, and that this is also true of adults.

Concerningly, the study found that single hot days were as bad as heatwave days, and moderately hot weather also had an impact. This differs from the impact of heat on physical illness, such as acute myocardial infarction and cerebrovascular accidents, which are known to worsen over subsequent heatwave days. The mechanism of heat increasing youth suicidality seems to begin to increase at milder temperatures and continued to increase as it gets hotter, showing a dose response effect consistent with a biological mechanism.

When looking at the regions most affected by hot weather, inland regional areas and western Sydney had higher rates of youth emergency presentation with suicidal thoughts and behaviour, even at the same temperatures. While at first, one might think this was expected for areas with many people living with socio-economic disadvantage, the largest Australian study of children and adolescent mental health did not link rates of youth suicidality in Australia to socio-economic status. In contrast to these previous findings for suicidality among young people, heat-related youth suicidality is higher, pointing to factors such as energy poverty (lack of air conditioning or inability to afford to run existing air conditioning), inadequate housing and building quality and lack of access to green and blue space to escape the excessive heat. In addition, in western Sydney, there is an urban heat island effect, which means that people are exposed to higher temperatures.

Clinical implications

Doctors working in general practice, community mental health and hospital settings, including emergency departments in Australia, can expect to see more young people presenting with mental distress, including suicidal thoughts and behaviours as hot weather continues to increase as a result of fossil fuel driven climate change. Awareness that children and young people staying comfortably cool in the heat is protective against mental distress is important information for young people, parents and carers.

Freely available, evidence-based information on ways to reduce exposure to excessive heat is already here. A fact sheet from the Sydney Children’s Hospitals Network on heat and mental health provides helpful information. The HeatWatch app, which while not specific to mental health, provides evidence-based guidance on staying healthy in hot weather. An infographic from The Lancet is available showing sustainable and accessible ways to stay cool.

It is also important to note that contrary to popular belief, a recent study published in The Lancet showed that many psychotropic medications prescribed to young people (such as selective serotonin reuptake inhibitors) are not associated with increased risk of heat-related illness and a decision to reduce or stop medication, such as for depressive or anxiety disorder, should be taken in the context of weighing the risks and benefits for that individual.

Public health implications

Emergency presentations with suicidal thoughts and behaviours are indicators of severe mental distress and risk factors for subsequent death from suicide. Given that suicide is the leading cause of death among Australians aged 12–24 years, public health measures on mitigating and adapting to increasing temperatures to reduce youth suicidality need to be prioritised. Current public health messaging on heat focuses on heatwaves and risks of physical illness. To this, we need to add single hot days and their risks to youth mental health. 

Phasing out fossil fuels is essential to improve youth mental health

Climate change is being driven, predominantly, by continued extraction and burning of fossil fuels, including gas, oil and coal. Despite our small population, Australia is in a unique position to reduce fossil fuel driven climate change as the second largest exporter of fossil fuels on the planet and having world-leading access to renewable energy from solar and wind. By taking into account the costs of ongoing fossil fuel extraction to health, including youth mental health, in any government decision on fossil fuels, Australia can turn from being a laggard to a leader on protecting human health globally.

Conclusion

As doctors, we prepare for seeing more young people with suicidal thoughts and behaviour and act to protect human health from heat locally, we have a duty to call for our leaders to take bold action to move our energy systems from polluting fossil fuels that are driving global heating to clean power. Failure to do this is like trying to prevent smoke-related lung disease without addressing tobacco.

Dr Cybele Dey is a child and adolescent psychiatrist, dual qualified as a paediatrician and a researcher at UNSW Sydney. She is the lead author of Youth suicidality risk relative to ambient temperature and heatwaves across climate zones: A time series analysis of emergency department presentations in New South Wales, Australia. 

Dr Lai Heng Foong is an emergency physician based in Sydney and the chair of the Public Health and Disaster Committee of the Australasian College for Emergency Medicine and conjoint senior lecturer for UNSW and WSU.  

Dr Emma Skowronski is a GP in Sydney but has worked in rural NSW and remote NT in the past. She enjoys holistic family practice and women’s health and has a passion for Aboriginal health and wellbeing. 

Dr Dey, Dr Foong, and Dr Skowronski are members of Doctors for the Environment Australia.

The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated. 

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