Daniel Teklemariam is the Julia Anderson Communications and Events Trainee in Climate and Mental Health, joining the Climate Cares Centre in summer 2025.
The Climate Cares Centres is a team of researchers, designers, policy experts and educators working to understand and support mental health in the current climate and ecological crises. Our mission is to equip individuals, communities and systems with the knowledge and resources to protect mental health from climate impacts, while enabling climate action that strengthens the conditions for good mental health and wellbeing.
Introduction: The Overlooked Link Between Heat and Mental Health
The recent European heatwaves killed thousands across the continent and hundreds in London, with a report by Imperial’s Grantham Institute revealing that 65% of the heat deaths were a direct consequence of human-induced climate change. But whilst the physical impacts of extreme heat like dehydration, heatstroke and death are more well known (source, source 2), the significant impact on mental health is often overlooked in public discourse, policy and research. Heatwaves can worsen symptoms of many mental health conditions whilst also making it harder to deal with heat when taking medication (Source), and this will become a growing issue over the next century as climate change will cause more frequent, severe, and early-season heatwaves across the globe. National, regional, and local authorities have developed heat-health action plans to deal with the health risks associated with heat but a recent review, done in collaboration with Climate Cares, found only 22% of such plans included targeted interventions for mental health. We need to highlight this overlooked aspect of extreme heat in public discourse and include it in our actions to respond to heatwaves to save lives and protect mental health in a changing climate.
Heat and Mental Health
How Heat Affects the Mind and Body: The Biological Connection
People commonly recognise that extreme heat affects mood but understanding the biological reasons is key to knowing why mental health is at risk. As temperatures rise, the body releases more cortisol, the primary stress hormone, which heightens feelings of agitation, anxiety, and mood instability (Source). Simultaneously, high temperatures suppress the parasympathetic nervous system, which is responsible for calmness and emotional regulation, leaving individuals more vulnerable to stress and less able to recover physiologically (Source). This imbalance can lead to insomnia, irritability, listlessness, and depressive symptoms during heatwaves (Source). Additionally, the neurotransmitters that regulate mood (such as dopamine, serotonin, and norepinephrine) are also essential in the body’s temperature regulation processes (Source). Disrupting these systems may explain why many individuals, especially those with pre-existing vulnerabilities, experience worsened mental health during periods of extreme heat.
Sleep Disruption and the Heat-Mental Health Cycle
Elevated night time temperatures significantly disrupt the body’s ability to regulate sleep. Heat exposure interferes with thermoregulation, a core process for initiating and maintaining restful sleep. Specifically, high temperatures reduce time spent in slow-wave and REM sleep, crucial phases for memory consolidation, emotional processing, and psychological restoration (Source). This leads to insomnia, fragmented rest, and early morning awakenings.
Poor sleep caused by heat has a direct negative effect on mental health. Sleep deprivation is strongly linked to elevated levels of anxiety, irritability, and depressive symptoms, as well as reduced cognitive performance and emotional regulation (Source). Impaired sleep also worsens existing psychiatric conditions and can increase impulsivity and risk-taking behaviours. A national survey in the UK found that 52% of people struggle to sleep during hot weather, underscoring the widespread impact of rising temperatures on public mental wellbeing (Source). Given these multi-layered effects, heat-related sleep disruption represents a critical but often overlooked component of the broader climate-mental health crisis, one that disproportionately affects both urban populations and socioeconomically disadvantaged groups.
Heat Can Affect Everyone—Even Those Without Diagnosed Conditions
For those without mental health issues, the effects of extreme heat are easily seen in the undermining of mental functioning and the increase in negative or anti-social behaviours. Studies have documented cognitive performance declines of up to 10% during exposure to heat above 26 – 28 °C (Source). And many studies have demonstrated a rise in aggression and interpersonal conflict as ambient temperatures climbed (Source). The heat makes people more frustrated, aggressive, and impulsive which leads to rising crime rates globally. One study by Matthew Ranson estimated that climate change will cause millions of crimes in the US that wouldn’t have happened without the rise in temperature (Source).
The Climate Cares Centre led Connecting Climate Minds which brought together over 1100 experts in more than 120 countries to identify priorities for climate-mental health research and action. In Malta, Claire Bonello emphasised that “In summer basically anything that people will be talking about is related to heat and how hot it is and how frustrated they are” and halfway around the world in Central and South Asia, they described heat as “a vicious cycle for people who have nothing” where heat leads to water shortages which leads to food shortages and job issues which then all lead to mental health problems. In Aruba, the rising temperatures and heatwaves have worsened drought conditions and damaged the soil which means that traditional farming can’t be sustained, and the loss of culturally important food will negatively affect locals’ mental health. Nigel Maduro is a sustainability scientist and an Indigenous Aruban activist who contributed to the People’s Petition to the International Court of Justice, and he says that “elders are telling us: “It’s not the same heat as back in the days” … Shall we wait until we overheat to death? Or do you want more proof that our human rights are being violated?.” Collectively, these findings show that thermal stress impairs cognitive processing, emotional regulation, and social behaviour even among otherwise healthy individuals.
Heat’s Amplified Toll on People with Mental Health Conditions
Extreme heat has been definitively shown to significantly exacerbate risks for individuals living with mental health disorders. Research of more than 2 million mental health related emergency visits demonstrated that each 1.8°F (1°C) increase in ambient temperature is linked to a 2.2% rise in mental health-related mortality and a 0.9% increase in morbidity for people living with mental health disorders compared to those without (Source). Other research found psychiatric patients in New York City had twice the risk of dying during a heat wave than the general population (Source). Conditions such as anxiety, mood disorders, schizophrenia, substance use disorders, self-harm, and childhood behavioural disorders can be worsened at higher temperatures (Source). People prescribed psychotropic medications, including antidepressants, antipsychotics, and lithium, face elevated risk due to these drugs’ impairment of the body’s thermoregulatory mechanisms, increasing vulnerability to heat exhaustion and heat stroke (Source). The impact of heat extends beyond physical health to influence psychiatric symptoms and behaviours. Suicide rates have been shown to increase with rising temperatures in England and Wales (Source, Source). Gender, age, and specific diagnoses further modulate these heat effects: for instance, elderly populations and males with depressive disorders experience disproportionate risks during heat events (Source). These findings emphasise the need for targeted interventions to protect mentally ill populations amid escalating climate-induced heatwaves.
Heat and its Societal impacts
Who Is Most Vulnerable? A Look at Disproportionate Impacts
Age
When considering policy and solutions to deal with extreme heat it is vital to highlight that certain demographics face amplified risks due to biological, social, and medical vulnerabilities. Older adults and individuals with chronic physical or psychiatric conditions are at elevated risk, as their ability to regulate body temperature is often compromised (Source). Those with disabilities, neurodivergence, or pre-existing mental illness—particularly males and older adults—face a higher likelihood of psychiatric deterioration during heatwaves (Source).
Young people are also especially vulnerable. As child and adolescent psychiatrist Dr Joshua Wortzel notes, for “every 1°C increase above the average summer temperature, there’s a 3% rise in suicide rates among young people,” a rate comparable to large natural disaster surges like Hurricane Katrina. According to Dr Wortzel the reason children might be more at risk is physiological: “they have a greater surface-area-to-volume ratio, sweat less efficiently, which means they can struggle to thermoregulate compared to adults.” Meanwhile, climate anxiety is increasingly common with 60% of youth being “very” or “extremely” worried about climate change, and 45% stating it disrupts their daily lives (Source). However, for young people experiencing severe mental illness this number drops to 15% which he thinks is caused by “more active, personal issues that they are struggling with, like parents going through a divorce or domestic abuse.” But Dr Wortzel believes that the impact on daily life for children in the global south is more significant as “countries with significantly lower GDP, the number of young people reporting that distress about climate change affects their daily life and function is as high as nearly 75%,” which makes sense when considering the accessibility to air-conditioning and water in the global north.
Socio-economic factors
Even in high-income countries the disparity in the effects is extreme. The disparities are caused by the urban environments where we have created heat islands due to heat-absorbing concrete and low greenery. Urban heat islands can elevate local temperatures by 2–10 °C, intensifying health hazards in dense built environments lacking sufficient green space. Heat stress is unequally distributed: low-income communities (including areas predominately with ethnic minority communities) often have less access to air conditioning and are more likely to live in high-heat neighbourhoods with denser housing (source). The effect can be seen notably in a 2018 study involving Boston-area university students which revealed that those in non–air-conditioned dormitories during a heatwave took approximately 13% longer to complete standardised cognitive tasks compared to their peers in air-conditioned buildings (Source).Students from low-income backgrounds are more likely to end up in cheaper student accommodation and so more likely to suffer in heatwaves with cognitive function and mental health issues.
Geography
Regional and international variations also exist; in the U.S., the Northeast, Midwest, and Northwest may be at greater risk than the South due to housing stock less adapted to high heat. Rapid, unplanned urbanisation in the Global South likewise compounds vulnerability, especially where informal housing offers minimal thermal protection (Source). Studies have shown that there will be increases in mortality in these urban sprawl environments and with the urban population in the developing countries growing to 4 billion by 2030 the impacts will be significant.
Straining the System: How Extreme Heat Pressures Healthcare and Society
Extreme heat drives notable spikes in attempted and completed suicide attempts, emergency department visits and hospital admissions, and worse outcomes for mental health conditions. According to Dr Emma Lawrance, Climate Cares Centre Lead, “the added strain on the healthcare system is significant.” In a comprehensive study published by the Climate Cares Centre researchers a 1°C increase in mean daily temperature was associated with a 1.7% increase in suicides worldwide. Another study found that on the hottest days, ED visits for mental health conditions such as anxiety, mood disorders, schizophrenia, substance abuse, and self-harm increased by 8%, depending on region, gender, and age (Source). Similarly, California data indicates that every 10°F increase correlates with a 4.8% rise in overall mental health–related ED visits, including intentional self-harm and assault (Source). These admission surges place considerable strain on health services and leaders and policymakers need to be more prepared and need to create adaptation strategies for heatwaves according to Climate Cares.
However, even institutions like psychiatric wards aren’t immune: Dr Lawrance warns that there are spikes in incidents at wards during heatwaves and this is supported by a Special Rapporteur who said “Mortality, owing to heat waves and climate change, disproportionately impacts people who are institutionalised” (Source). Dr Lawrance says, “Institutions that are supposed to protect and treat people with psychiatric conditions can be exacerbating their symptoms if they aren’t equipped to address the impact of heatwaves on mental health conditions” by appropriately cooling them during high temperatures. The heat exacerbates aggression and interpersonal violence, compounding pressure across both healthcare and justice systems whilst elevated temperatures can destabilise mental health and interfere with medication efficacy, further increasing hospital visits for physical ailments linked to psychiatric treatment. According to Professor of Psychiatry at the University of Nevada School of Medicine Dr Elizabeth Haase, “It will become more common to have 2-3 people per 20 who are more violent than normal and more actively suicidal in a psychiatric emergency room – and that will be a noticeable increase in stress on the system.” This strains and stretches resources on a small scale and when amplified to every healthcare facility worldwide the implications become clear.
The symptoms caused by extreme heat also have social implications as analysis links each 10°C rise to approximately a 9% increase in violent incidents (Source). Women and marginalised populations face disproportionate risk for example; intimate partner violence has been observed to increase in heat-stressed communities underscoring deep social inequities (Source). The American Psychiatric Association does provide educational webinars and presentations on heat and mental health, but Dr Haase thinks the impact is limited because “It doesn’t trickle down to people being required to something about heat and mental health.” Collectively, these dynamics highlight the urgent need for heat-informed emergency readiness across healthcare and other public systems.
Climate Change: The Driver Behind More Frequent Mental Health Crises
It is important not to separate extreme heat and heatwaves from climate change. Global heatwave exposure has doubled since the 1980s, making climate-driven thermal stress a critical public mental health threat (Source). It is increasing the frequency and severity of extreme heat events whilst also bringing in early-season heatwaves which result in greater health impacts due to lack of acclimatisation. Even without heatwaves global warming projections based on the current policies and actions estimate a 2.7°C increase in temperature by 2100 (Source). Without human-induced climate change, early heatwaves of the temperatures observed would have been much rarer. Imperial’s Grantham Institute has claimed that in all cities, apart from Lisbon, the 2025 heatwaves of the observed frequency would have been 2-4°C cooler (Source). This increase in temperature doesn’t sound deadly but in the recent June/July heatwave it is estimated that climate change caused 1504 excess deaths over 10 days in 12 cities which at times can feel 5°C hotter than suburbs or the countryside. The mental health effects of this many deaths on people are devastating and some like Dr Wortzel support framing heatwaves as an extreme weather event like other chronic environmental disasters (sea levels rising, chronic drought). And with children born in 2020 being exposed to seven times the number of heatwaves as their grandparents (Source), people within psychiatry and climate change need to push policymakers to include climate change and mental health in their heat-action plans.
Policy and Interventions
Mental Health and Heat Action Plans
Despite mounting evidence that extreme heat negatively impacts psychological well-being, mental health remains poorly integrated into most heat-health action plans. A global review of 83 plans done in collaboration with Climate Cares found that only 31% explicitly acknowledged mental health, and only 22% fewer included targeted strategies for intervention (Source). According to Policy and Advocacy Advisor for United for Global Mental Health Dr Alessandro Massazza, “most of the evidence we have on this topic comes from high-income countries, leaving a major knowledge and implementation gap in lower-income settings where heat risks are often most acute.” It’s also important to recognise that there still isn’t enough data on mortality rates due to heatwaves in the global south. This is especially true in South Asia where there are decades’ worth of missing data (Source). The scientific knowledge on mortality rates globally is low but the scientific knowledge on mental health impacts is almost non-existent. It is vital to include mental health in heat action plans but there needs to be a more concerted effort by the international community to further study the connection.
Even when mental health is mentioned in national adaptation or climate strategies, Dr Massazza notes that there is a “disconnect between identifying the problem and proposing actionable solutions.” This mirrors findings in a recent WHO assessment of how health is included in national adaptation planning, which found that, of all health outcomes, mental health has the largest gap between coverage of health impacts and recommendations for action. (Source)
Part of the challenge, Dr Massazza argues, is the lack of evaluated interventions: “There are many promising programmes already happening, especially at the community level, but they’re not being systematically studied.” This research gap, paired with chronic underinvestment in mental health within climate adaptation funding, means that vulnerable populations—especially those with psychosocial disabilities—are frequently overlooked or “lumped in without tailored support.”
Dr Massazza views mental health as an accelerator for climate action as well as an impact of climate change and for him the message is clear: “Ambitious climate action is ultimately a mental health intervention and achieving the goals of the Paris Agreement is a way of safeguarding mental health globally.”
Strategies and Interventions
Funding
In 2013, the IPCC report barely mentioned health outcomes of climate change and now Dr Haase views health and mental health as having become “a big focus of organisations like WHO or the COP, who are talking about it more and more.” She was one of the founders of the Climate Psychiatry Alliance in 2017 and she has seen the evolution of health and mental health in heat response plans in the last 4-5 years. However, she recognises that for real change to come there must be funding. “All the projects that current climate mental health experts are going to do are going to be small because there’s no ability to do a project that you get paid for,” which is why the CPA is made up of passionate climate psychiatrists who volunteer in their free time. In her opinion, “there are no dollars in climate mental health funding” but this is an approach that Dr Feder strongly opposes because of the cost-saving benefits of preventative programmes which he describes as “relatively inexpensive compared to the consequences of emergency room visits”. The shared opinions around funding are backed by a recent Rockefeller Foundation review which showed that out of all health outcomes, mental health financing was some of the lowest (Source). In Dr Massazza’s opinion “Mental health tends to be disproportionately neglected in the context of funding and financing and that is the equally true in the context of climate change,”
Resilience
Whilst climate mitigation is vital there are effects of climate change that are unavoidable now and in the future. In these circumstances communities and people need to be fully equipped to cope with the impacts of climate change. Some of the interventions developed to help deal with extreme heat focus on the idea of resilience to climate change. Resilience is defined by the IPCC as “the capacity of social, economic, and environmental systems to cope with a hazardous event… while also maintaining the capacity for adaption, learning and transformation”. This can be resilience to climate disasters or resilience to heatwaves. Community groups and campaigners organise without the help of larger institutions, where their programmes have been developed by local people to address local problems they deal with (Source). Some programmes in America are supported by Dr Bob Doppelt’s International Transformation Resilience Coalition which has recently been pushing a bill called the US Community Wellness and Resilience Act which would establish more of these programmes in the country.
Intervention for children
For young people, experience and awareness of climate disasters, like more intense monsoon seasons or heatwaves cause more distress and anxiety. Many of these climate disasters are inevitable in the short and long term even if we move closer to the goals of the Paris Agreement. In communities that regularly experience extreme heat and heatwaves it is crucial to create and implement interventions to help young people to cope with their emotions and distress. Interventions like Problem Focused Coping get young people engaged in addressing climate change through activism or campaigns. Dr Wortzel says that “getting young people involved, particularly in groups rather than alone, can help reduce their climate distress.” This helps provide a framework for larger community or school-based actions but for kids who feel like climate change and extreme heat gets in the way of their ability to function the Cognitive Behavioural Therapy methods of Emotion Focused Coping can help stop negative spirals. Meaning Focused Coping based off Viktor Frankl’s Logotherapy is about “trying to help people find purpose in the face of great adversity”, which applied to this scenario is climate change and extreme heat. Helping young people build resilience by giving them meaning in the world through advocacy and a sense of stewardship.
Education and Interventions
Dr Massazza emphasises the need for meaningful integration of mental health into early warning systems. He points to the state of South Australia’s system, where individuals with known psychiatric conditions receive check-in calls before and during heatwaves—and if unresponsive, are visited by emergency services. “It’s a concrete example of how mental health can be proactively protected,” he explains. Yet such programmes remain rare globally as only 35% of countries reported having health early warning systems for heat-related illness, and just 10% had this in place for mental and psychosocial conditions (Source). Whilst psychiatrists who lead in the field have studied the connection, most agree that the information doesn’t trickle down to people in healthcare who must work with patients with mental health conditions. There isn’t any requirement for clinicians to know this information which is why Dr Haase supports developing a screening tool with a points system to work out how vulnerable a particular person is. For Dr Haase, the idea of a heat risk checklist is “some minimal kind of a safety net” and to be easily usable will need to be “simple enough so an intake worker or medical assistant worker could fill out the data,” but then this database could help prevent future medical emergencies by working out if the person is a heat risk due to where they live being a heat island or if they have a medical condition (or take medicine) that puts them at greater risk. This, Dr Feder believes needs to be paired with an “education both for clinicians and patients with psychiatric conditions” due to the lack of awareness around the increased risk during heatwaves.
All these changes need to be created through policy initiatives in heat action plans and through groups like Climate Cares, Connecting Climate Minds, the Grantham Institute, the Climate Psychiatry Alliance and funders. Dr Feder wants to stress that climate action seemingly unconnected to mental health can be seen as a co-benefit for mental health. In the context of extreme heat in urban areas this could include green spaces, cooling spaces, accessible public transport, and buildings designed to stay cool during warmer periods (Source). Dr Lawrance thinks, “The next best step is to make sure policymakers and decision-makers are aware of and account for the impact of extreme heat on mental health through appropriate adaptation actions.”
Conclusion: Preparing for the Heat Means Preparing for Mental Health
With climate change escalating global temperatures, mental health must be integral to heat resilience and climate policy. Strategies should prioritise preventative measures like education and community interventions whilst heat must be considered in all aspects of city planning through cooling infrastructure like A/C and green spaces. Mental health services should prepare for heat-driven case surges and governments need to support this process by funding research on interventions and implementing policies that target the mental health impacts of extreme heat. By acting now, societies can foster psychological adaptability to heat extremes by developing collective resilience. However, as Dr Lawrance of Climate Cares says, “The ultimate prevention would be to stop burning fossil fuels to minimise the impacts of climate change as fast as possible.”
Find out more about the Climate Cares Centre’s work on this topic:
- Connecting Climate Minds: a global initiative that heard from 1100+ experts in over 120 countries to inform a series of research and action agendas on climate change and mental health. With a focus on centering lived experience perspectives, this work highlighted research priorities to improve understanding of the links between temperature and mental health, to drive action.
- People’s Petition — Future Generations Tribunal : a report elevating the voices of witnesses from around the world experiencing the most severe impacts of climate change, who came together in December 2024 to influence the International Court of Justice.