Psychiatrists should champion the care of those with severe mental illnesses experiencing climate change-related heat stress

Abstract

Objective

The Australian climate has warmed by 1.51°C since preindustrial times, and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) predicts further warming with an increased risk of extreme heat events. This article discusses how the most recent Royal Australian and New Zealand College of Psychiatrists’ (RANZCP) position statement dealt with the impact of climate change-related heat stress on people living with severe mental illness.

Conclusions

The RANZCP statement focuses on the impact of climate change on common mental disorders and suicide rates without specific mention of severe mental illnesses such as schizophrenia, bipolar disorder and severe major depression. However, people with severe mental illness face higher risks of morbidity and mortality in a hotter Australian climate. Based on equity for those with greater needs and higher levels of risk, we argue that psychiatrists should advocate for enhanced social and psychiatric care to improve heat-resilience amongst patients with severe mental illness. Future research is needed on the biopsychosocial mechanisms of increased heat-related morbidity and mortality for people with severe mental illness.

‘The climate and ecological emergency facing humanity is increasingly affecting the health and wellbeing of populations across the globe’ (Royal Australian and New Zealand College of Psychiatrists, 2021).

In a 2021 position statement, the Royal Australian and New Zealand College of Psychiatrists (RANZCP) conveyed key messages about the impact of climate change on anxiety, depression and suicide rates (Box 1). ¹ However, we were unable to locate specific mention of severe mental illnesses such as schizophrenia, bipolar disorder and severe major depression in the statement, and there were no specific key messages prioritising severe mental illness. In the context that the RANZCP is committed to supporting and developing further discussion to better understand the impacts of climate change and how they relate to mental health (Box 1), we advocate that psychiatrists should give greater weight to the most severe and disabling illnesses. This perspective article defines the term ‘global heating’, argues for greater equity for those with the most disability and examines Australia’s hotter climate as a risk factor for severe mental illness.

Box 1: RANZCP key messages on the mental health impacts of climate change

• Climate change is a global threat to health and wellbeing and is impacting the mental health of individuals and communities.

• The RANZCP recognises increasing mental health disorders and rates of suicide associated with the impacts of climate change.

• The RANZCP acknowledges that mental distress caused by the real threat of climate change is an appropriate response. Climate change contributes to clinical disorders such as anxiety and depression that will greatly impact morbidity and mortality across the globe. Psychiatrists have the opportunity to support individuals and communities to enhance resilience and take action to mitigate the impacts of climate-related anxiety and depression.

• Improved dissemination of existing research and further research is required to better communicate and understand the cumulative impacts of climate change on mental health and how it can best be addressed in psychiatric practice. The RANZCP is committed to supporting and developing further discussion to better understand the impacts of climate change and how they relate to mental health.

• The RANZCP is committed to turning concern into action through adopting sustainable business practices and through reducing its own carbon footprint.

Source: Royal Australian and New Zealand College of Psychiatrists (2021) The mental health impacts of climate change. Melbourne, VIC, Australia: Royal Australian and New Zealand College of Psychiatrists.

Global heating and the Australian climate

Heat stress has particular relevance to severe mental illness, so we use the term global heating, which is defined as increased average global temperatures since preindustrial times, due to rising levels of anthropogenic greenhouse gases such as CO2 that trap heat on the planet. ² By 2023, the average global temperature had risen by 1.45°C since preindustrial times, resulting in one-third of the world’s population being exposed to extreme heat events. ³ Paleoclimate records indicate that atmospheric CO2 is at its highest level since the Pliocene Climatic Optimum 4.4 million years ago when average global temperatures were 2°C–3 C hotter. ³

Australia’s climate has warmed by 1.51°C since national records began in 1910, and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) predicts continued warming with increased chances of extreme heat events, more fire weather and megafires, drought and desertification, heavy rain with more flooding and rising sea levels with inundation along the Australian coastline. ⁴ If these predictions are correct, these events will disrupt human populations, affecting the health and wellbeing of people with severe mental illness.^5–7

Equity for those with severe mental illness

The first issue that we address is equity for severe mental illness. Currently, there is a strong trend in Australian mental health policy to focus on ‘broader, looser, and more benign’ concepts of mental health in the population, which has resulted in the neglect of public sector adult mental health services that care for people with severe mental illness.^8,9 The rise in climate-related anxiety in the community may accentuate this trend with governmental attention being diverted further away from severe mental illness. Given a focus on climate-related anxiety in research and policy, governments may be more inclined to fund low-intensity interventions for the milder psychological consequences of climate change, based on transdiagnostic and dimensional indicators of climate anxiety in the population, self-report questionnaire surveys and social media opinion, rather than directing resources to those with severe mental illness who face greater risks of morbidity and mortality from climate change (Box 2). ¹⁰

Box 2: Proposed international research agenda for climate change and mental health

• ‘Move beyond’ administrative hospitalisation and mortality data.

• Cover the entire spectrum of severity and good mental health.

• Operationalise emergent constructs such as climate anxiety.

• Develop transdiagnostic and dimensional indicators.

• Improve assessment using self-report questionnaires.

• Use proxy measures such as social media data.

• Fund low-intensity psychological support interventions.

Source: Massazza A, Teyton A, Charlson F, et al. (2022) Quantitative methods for climate change and mental health research: current trends and future directions. Lancet Planetary Health 2022 6: e613-e627.

Psychiatrists should question calls for climate research to ‘move beyond’ the hospitalisation and mortality data that record the effects of extreme heat events on people with severe mental illness (Box 2). ¹⁰ Whilst we agree that climate anxiety is an important signal of increasing community concern about the existential threat of climate change, this phenomenon could more accurately be described as ‘climate distress’, if it is based on an entirely rational appreciation of the dangers presented by climate change.^11,12 Governmental action should therefore focus on mitigating the real-world threat of climate change rather than funding psychological interventions for reality-based climate distress.

Moreover, giving priority to climate anxiety runs counter to the principle of vertical equity, which indicates that greater attention and resources should be directed towards those with greater needs. ¹³ To strive to equalise outcomes, severe mental illnesses should be prioritised over milder psychological distress, as measured with transdiagnostic and dimensional indicators. The associated principle of horizontal equity means giving equal attention to those with equal needs, so therefore people with severe mental illness should have equal access to psychiatric care regardless of race, gender, sexuality, socioeconomic group or geographic location (e.g. rural and urban areas). ¹³

To operationalise vertical equity in mental healthcare, we suggest adopting the ‘health state weights’ developed by the World Health Organization (WHO), which estimate disability on a scale from 0 (perfect health and no impairment) to 1 (a state equivalent to death). ¹³ On this measure, acute schizophrenia is the most disabling illness amongst 220 physical and mental health conditions with severe multiple sclerosis being the second most disabling. Schizophrenia has a health state weight of 0.778, so during an acute episode a person is estimated to have only a fifth of the functioning of a fully healthy individual. ¹³ At the other end of the spectrum, mild climate-related anxiety disorders would have a health state weight of 0.03, which indicates minimal disability. ¹³

People with schizophrenia also have poorer health, economic and social outcomes than the general population, and their life expectancy remains nearly 20 years lower than average. ¹⁴ With constrained Australian mental health budgets, vertical equity, as operationalised with the WHO health state weights, indicates that adult mental health services for schizophrenia should be ranked over low-intensity psychological support for milder forms of climate anxiety.

Calibrating psychiatric care for heat stress effects on severe mental illness

The second issue we highlight is the additional risks that Australia’s hotter climate present for people with severe mental illness. A recent systematic review of healthcare demand for those with mental illness found a link between primarily heat-related weather events, emergency room visits and hospital admissions. ⁵ This review indicated that sustained heat of 7 days increased the relative risk of healthcare contact by 2.49 (95% confidence interval: 1.69–3.69) for people with schizophrenia, as well as increased healthcare demand for those with bipolar disorder. ⁵ Adults over 60 were also identified as a high-risk group for increased healthcare demand related to global heating. ⁵

Extreme heat events also increase mortality risks for people with schizophrenia, due to impaired thermoregulation and less ability to compensate for heat.^15,16 A recent epidemiological study of an extreme heat event in British Columbia, Canada, found people with schizophrenia had the greatest mortality risk amongst 26 chronic diseases with an odds ratio of 3.07 (95% confidence interval: 2.39–3.94) when compared to mortality rates in non-heat event periods. ¹⁷ An earlier study from Adelaide, Australia, found that mortality attributed to schizophrenia-type disorders was doubled (incidence rate ratio 2.08; 95% confidence interval: 1.05–4.14) during extreme heat events compared with non-heat event periods. ¹⁸

More recent Australian studies have found that mental health admissions were a major contributor to the additional hospital demand attributable to hotter weather in Sydney and Perth.^6,7 Australian hospital costs are likely to increase in the future, due to heat-associated mental health admissions.^6,7

Additional risk factors amongst those with severe mental illness include social isolation, economic marginalisation, accommodation without air conditioning, urban heat island effects, wearing excess clothes and substance use, which increase mortality rates during extreme heat events (Box 3).^19,20 Epidemiological evidence indicates the psychotropic medications used in the treatment of severe mental illness such as antidepressants, anxiolytics and antipsychotics are linked with increased morbidity and mortality risks during hot weather. ¹⁶ These drugs might further impair thermoregulation. However, a recent review found a paucity of studies examining the effects of heat stress on core body temperature with psychotropic medications and recommended further heat stress studies of antipsychotics and antidepressants with strong anticholinergic properties as well as more studies of women and people with comorbid chronic diseases. ²¹ Some studies report higher serum lithium levels in hotter weather, potentially increasing the risk of lithium toxicity with dehydration, although a recent study from Sydney found no clinically important correlation between serum lithium concentrations and temperature. ²² Future research is required to better understand the biopsychosocial mechanisms that increase heat-related morbidity and mortality amongst people with severe mental illness.

Box 3: Risk factors for heat-related morbidity and mortality

• Schizophrenia, schizotypal and delusional disorders.

• Marginalisation with social isolation, poverty or homelessness.

• Comorbid physical conditions.

• Living in neighbourhoods with urban heat island effects.

• Accommodation without functional air conditioning.

• Impaired thermoregulation due to schizophrenia.

• Redundant clothing contributing to overheating.

• Antipsychotic medication reducing heat tolerance.

• Lithium toxicity due to dehydration.

• Psychosis decreasing comprehension of public health warnings.

Australia adult mental health services should prepare for escalating demands due to the hotter Australian climate and take appropriate measures to improve heat resilience amongst people with severe mental illnesses (Box 4).^19,20 These include checking at-risk individuals on high temperature days and reviewing medication that might conceivably affect thermoregulation in summer. Unfortunately, adult mental health services have been subjected to ‘decades-long corrosion of care, due to an insufficient supply of resourcing, infrastructure and personnel’. ²³ To alleviate this neglect, additional resourcing will be required for community and hospital mental healthcare as Australia’s climate becomes hotter. ⁹ Australian federal and state policy and commissioning units need expertise in adequately meeting the needs of people with severe mental illness in this hotter climate that is informed by data tracking of longitudinal outcomes (i.e. administrative hospitalisation and mortality data).^5,14

Box 4: Increasing resilience to extreme heat events

• Checking at-risk patients on high temperature days.

• Reviewing medication that may affect thermoregulation.

• Educating caregivers and patients about heat stress.

• Posters on heat-related harm in community clinics.

• Building air conditioned mental health respite spaces.

• Lists of public cool spaces displayed in clinics.

• Advocacy for community projects such as tree planting.

Source: Green S, Rosenbaum D, Beder M (2024) Heat Resilience and Severe & Persistent Mental Illness. Canadian Journal of Psychiatry 69: 239-241.

Implications for psychiatry across the life span

CSIRO forecasts that the Australian climate will continue the trend towards hotter and more arid conditions due to greenhouse gases and related factors (Box 5). ⁴ With this hotter climate and more high temperature days, youth, adult and older age psychiatry should advocate on behalf of those with the greatest needs and highest risks of heat stress. As well as additional social and psychiatric care to improve heat-resilience especially among those older than 60, people with severe mental illness need housing with effective insulation, reliable air conditioning and affordable energy especially where more heating is forecast in the remote heartland. ⁴ Sustained expert advocacy by psychiatrists could shift Australian climate change mental health policy away from ‘broader, looser and more benign’ constructs such as climate anxiety towards greater equity for severe and disabling illness. ⁸ Prioritisation on the basis of ‘severity’ is necessary to address the impact of heat stress in clinical practice and mental health policy, planning and budgets.

Box 5: CSIRO projections of a hotter and more arid Australian climate

Research in Australia and around the world, together with the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, enhances understanding of the state of Australia’s future climate. The changes are projected to include the following:

• Continued warming, with more extremely hot days and fewer extremely cool days.

• A further decrease in cool season rainfall across many regions of the south and east.

• Continued drying in the south-west of Western Australia, especially during winter and spring.

• Likely increases in the average duration of drought and aridity in regions within the south and east.

• A longer fire season for much of the south and east, and an increase in the number of dangerous fire weather days for many regions.

Source: CSIRO State of the Climate, 2024.