Heat and mental health: crises, admissions, suicide

A 34-year-old man with schizophrenia, stable for two years, arrives at the emergency department in Curitiba on the third consecutive day of unusual heat. His family reports that he barely slept, became irritable, stopped taking his medication and spent the afternoon locked in a room without ventilation. He is agitated, with hot, dry skin. The team first thinks of psychotic decompensation. No one measures his temperature in the first hours.

This scene brings together three problems that heat tends to bring together: worsening of the psychiatric condition, physical risk increased by medications that interfere with thermoregulation, and an assessment that separates mind and body when the patient needs both at the same time. The literature of recent years shows that ambient temperature affects psychiatric demand consistently, in rich and poor countries, in adults, older people and young people.

This text organizes what is known: the size of the effect, which disorders seem most sensitive, what happens with suicide, why some patients are at greater physical risk and what the clinician can do in the office and on shift.

Key points

• Hot days increase emergency visits and admissions for mental disorders.
• The effect appears in anxiety, mood, substance use, schizophrenia and self-harm.
• Suicide risk rises with temperature in many countries, including Brazil.
• Children, adolescents and young adults are also affected, not only older people.
• Antipsychotics, anticholinergics and diuretics can interfere with heat loss.
• During a heat wave, the agitated psychiatric patient needs a physical assessment, starting with temperature.

What temperature does to psychiatric demand

The question seems simple, but it only gained solid answers when large databases allowed comparing hot days and mild days in the same population. This design, called a time series, compares a person with themselves at different moments and reduces the weight of factors that do not change from one day to the next.

A recent review of people aged 60 or older gathered 76 studies (Byun et al., 2024). In a meta-analysis of four studies, each additional degree of temperature was associated with a relative risk of 1.014 for admissions or visits for mental disorders. During heat waves, admissions and visits rose with an RR of 1.269, in an analysis of six studies. For mortality from mental disorders, the RR was 1.266, but the confidence interval was 0.956 to 1.678, with only four studies, which does not allow a firm conclusion. The overall certainty of the evidence was classified as moderate, and cold also appeared as a risk factor.

These numbers seem small when read in isolation. The issue is scale. A modest increase in risk applied to millions of people, over dozens of hot days per year, translates into a lot of extra demand for services already working at their limit.

How to read these studies

Before going further, it is worth understanding what these numbers say and what they do not say. Almost all studies on heat and mental health are observational. They show that, on hotter days, the same population seeks mental health services more often. They do not, on their own, show why this happens, nor do they identify who will worsen.

Another point is the definition of heat. Some studies use the mean temperature of the day, others the maximum, others local percentiles or heat waves with a minimum duration. The definition of outcome also changes: emergency visit, admission, death or suicide. That is why the numbers should not be added together or compared directly across studies. What gives strength to the body of evidence is the consistent direction of the effect in such different places, periods and methods.

Finally, the effects usually appear on the same day or on the days following the heat, and many studies add this lag into a cumulative risk. For practice, this means that demand can remain high even after the temperature falls, and that the service should prepare for several days, not just for the peak.

Emergency and admission: what the large studies show

The largest study of emergency department visits in the United States analyzed 3,496,762 visits for mental disorders in 2775 counties between 2010 and 2019 (Nori-Sarma et al., 2022). On days of extreme heat, defined as above the local 95th percentile, the visit rate was 8 per 100 higher (IRR of 1.08). The effect was seen in almost every category:

• substance use, IRR of 1.08;
• anxiety and stress-related disorders, IRR of 1.07;
• mood disorders, IRR of 1.07;
• schizophrenia and other psychoses, IRR of 1.05;
• self-harm, IRR of 1.06;
• behavioral disorders beginning in childhood, IRR of 1.11.

Among men, the IRR reached 1.10. The study also assessed differences by age group, sex and region of the country, which helps show that the phenomenon is not limited to a single group.

In Bern, Switzerland, a study followed 88,996 psychiatric hospitalizations between 1973 and 2017 (Bundo et al., 2021). The risk of hospitalization rose 4.0 per 100 for each additional 10 °C. For schizophrenia, the increase was 10.0 per 100, and for developmental disorders it reached 29.0. This finding stands out because it comes from a city with a temperate climate, where extreme heat is less frequent.

In Adelaide, Australia, an analysis from 1993 to 2006 identified a threshold of 26.7 °C above which hospitalizations for mental and behavioral disorders began to rise (Hansen et al., 2008). During heat waves, these hospitalizations were 7.3 per 100 higher than in other periods. Mortality attributed to mental disorders also increased in the 65 to 74 age range and among people with schizophrenia. Dementia-related deaths increased in age groups up to 65 years.

What the Brazilian data show

Brazil has its own studies, and they help dispel the idea that the problem belongs only to rich countries or extreme climates.

In Curitiba, an analysis from 2010 to 2016 assessed the relationship between temperature and visits for mental disorders (da Silva et al., 2020). The relative risk associated with temperature was 1.0182 in men and 1.0407 in women, and older adults proved more susceptible in that period.

A more recent study in the same city analyzed 101,452 emergency visits for mental disorders between 2017 and 2021 (Corvetto et al., 2023). Comparing a day of extreme heat (24.5 °C mean temperature) with the median (18.02 °C), the cumulative risk was 1.15. Some groups stood out:

• suicide attempts, RR of 1.85;
• neurotic, stress-related and somatoform disorders, RR of 1.18;
• women, RR of 1.20.

This second study found lower risk in older adults (RR of 0.77) and in organic mental disorders (RR of 0.60). The difference from the earlier study shows that the most vulnerable group can change depending on the period, the definition of the outcome and the type of service analyzed. For practice, the message is that there is no single risk profile: heat affects different groups in different contexts.

It is also worth noting the threshold value. A mean temperature of 24.5 °C does not seem extreme to anyone living in the Northeast or Central-West. What matters is the heat relative to what is usual for the local population. That is why the studies use percentiles from the city itself, and not a fixed number.

Suicide, young people and temperature

The largest study on the topic analyzed 1,320,148 suicides in 341 locations across 12 countries (Kim et al., 2019). Brazil contributed 13 cities, between 1997 and 2005, totaling 8801 suicides. In the pooled analysis, the curve had an inverted J shape: risk increased with temperature up to a peak at 27 °C, where the RR reached 1.33. Among countries, the estimated RR ranged from 1.31 in the United States to 1.65 in Taiwan.

A systematic review with meta-analysis gathered 32 studies on temperature and suicide (Heo et al., 2021). The risk of suicide was 9 per 100 higher for each increase of 7.1 °C (RR of 1.09). The review also compared countries by income level and pointed to research gaps, such as the interaction between air pollution and temperature.

Since the risk peak falls at a temperature common in the summer of many cities, including Brazilian ones, the effect does not depend only on rare extreme events. It follows day-to-day heat.

In young people, a systematic review of 28 studies of people up to 24 years old found an association between heat and suicide, with an increase of 1.0 per 100 in risk for each 1 °C (Lai and colleagues, 2026). The same review found, under exposure to high temperatures, a higher risk of hospital visits or admissions for mental disorders (13 per 100), for schizophrenia (14 per 100) and for depression (18 per 100).

The Brazilian study in Curitiba, with an RR of 1.85 for suicide attempts in extreme heat, reinforces this signal (Corvetto and colleagues, 2023). These are population association data. They do not allow predicting who will attempt suicide on a hot day, but they indicate that surveillance must increase in these periods.

Children, adolescents and young adults

The idea that heat only affects frail older adults does not hold up in mental health data. In New York, a study of 82,982 emergency and hospital visits linked to mental health in people up to 25 years old found a clear association with heat (Niu and colleagues, 2023). On days of high temperature, the chance of an emergency or hospital visit increased with an OR of 1.28 between 6 and 11 years, 1.17 between 12 and 17 years and 1.09 between 18 and 25 years.

The youngest group was the most affected. Children depend on adults to protect themselves from heat, have less autonomy to change environments and may express discomfort through behavior, which matches the increase in behavioral disorders seen in the American study (Nori-Sarma and colleagues, 2022).

The review with people up to 24 years old reached the same conclusion (Lai and colleagues, 2026). For the pediatrician and the family doctor, this means including heat in the list of factors that may explain an acute behavioral worsening, alongside sleep, school, family conflicts and substance use.

Why heat worsens the mental picture

The mechanisms are not fully understood, but some pieces fit together. A review on the topic gathered physiological and behavioral explanations (Lõhmus, 2018). Heat harms sleep, and sleep deprivation is a known trigger of decompensation in mood disorders and psychoses. Heat also worsens executive functions, such as attention, planning and impulse control.

A more recent review, which combined four studies with six focus groups with 33 participants, 21 of them with experience of mental disorder and 12 health professionals, organized the pathways cited (Baecker and colleagues, 2025):

• activation of the hypothalamic-pituitary-adrenal axis and increased psychological stress, with still limited evidence;
• worse sleep and less physical activity;
• social isolation, associated with depressed mood;
• lower engagement in treatment, because physical discomfort reduces motivation to go to sessions or take medication.

In the focus groups, participants described irritability, frustration, loss of usual coping strategies and anxiety about their own health, which can lead to a spiral of worsening. This account helps explain why the effect appears in so many different categories: heat does not create a new disorder, but it reduces the margin of those already living near the limit.

Medications that interfere with thermoregulation

Here the topic stops being only psychiatric and becomes clinical. The body loses heat mainly through sweat and dilation of skin vessels. Some medications interfere with these mechanisms.

The review on mental health and heat describes two main groups (Lõhmus, 2018). Medications with an anticholinergic effect reduce sweat production, and sweat is the main way the body cools down in hot environments. Antipsychotics that block dopamine impair central temperature control and can cause muscle rigidity, which generates heat. The same review cites a classic study in psychiatric hospitals in New York State, with data from 1950 to 1984, in which patients had twice the risk of dying during heat waves compared with the general population. The risk was higher in the 1950s, before the widespread use of antipsychotics, than in the 1980s, which shows that medications do not explain everything: inpatient conditions and care also matter.

A study of 9721 Medicare patients assessed the risk of hospitalization for heat-related illness according to medication use (Layton and colleagues, 2020). Use of several classes on their own was already associated with higher risk, with RR between 1.16 and 1.37, including diuretics, anticholinergics and antipsychotics. During heat waves, the risk of hospitalization for heat rose by between 21 and 33 per 100 across the different classes analyzed.

This does not mean these medications should be stopped in summer. Abrupt discontinuation carries its own risks, including relapse, and the Medicare study was not designed to guide that decision. What changes is vigilance: people who use these classes need to know that heat is an added risk and have a plan for hot days.

Group	What the studies show	What to do in practice
Older adults with mental disorder	More hospitalizations during heat waves; cold is also a risk	Ask about ventilation, hydration and who accompanies them
Schizophrenia and other psychoses	More hospitalizations and more deaths in the heat across several studies	Measure temperature in every acute agitation in summer
Children and adolescents	More visits, especially at ages 6 to 11	Include heat in the assessment of behavioral worsening
Use of anticholinergics, antipsychotics or diuretics	More hospitalization for heat-related illness	Plan for hot days, without stopping on your own
Suicide risk	Risk rises with temperature in several countries	Strengthen follow-up and contact during hot periods

Who is most vulnerable

The studies vary, but some groups appear often. People with schizophrenia show up in almost all analyses as more sensitive, with more hospitalizations and more deaths (Hansen and colleagues, 2008; Bundo and colleagues, 2021). The likely explanation combines the effect of medications, the difficulty of noticing and reporting discomfort, and housing conditions.

Older adults appear as a vulnerable group in broad reviews (Byun and colleagues, 2024) and in some of the Brazilian studies (da Silva and colleagues, 2020), although the most recent study from Curitiba found the opposite pattern (Corvetto and colleagues, 2023). Children and adolescents appear with increased risk in emergency visits (Niu and colleagues, 2023). Men had a higher IRR in the American study (Nori-Sarma and colleagues, 2022), while women had a higher RR in the two Curitiba studies (da Silva and colleagues, 2020; Corvetto and colleagues, 2023).

This variation is a reminder that vulnerability depends on context. Income, housing, access to ventilation, support network and the type of service available matter as much as age or sex.

What to do in the consultation and on shift

The first step is to include heat in your reasoning. When faced with an acute psychiatric worsening during a hot period, it is worth asking how the person is sleeping, where they spend the day, whether they have access to water and ventilation and whether they are still taking their medication. These questions take a few minutes and change management.

The second step is not to separate mind and body. A patient with a mental disorder who is agitated on a hot day may have fever, dehydration, heat-related illness or an adverse medication effect. Temperature should be measured early. Hot, dry skin, confusion that does not match the patient's usual pattern or muscle rigidity call for clinical assessment before attributing everything to the psychiatric condition. Diagnostic uncertainty in this scenario is real, and the best strategy is to keep both hypotheses open.

The third step is preventive. For people who use anticholinergics, antipsychotics or diuretics, a conversation before summer about warning signs, hydration and cool environments costs little. Recording this guidance in the medical record helps the team pick the subject up again at follow-up visits.

The fourth step is suicide surveillance. The data do not allow us to say that a specific patient will get worse on a hot day, but they show that population risk rises. In mental health services, strengthening phone contact, bringing follow-ups forward and reviewing safety plans during hot periods are measures consistent with the evidence.

Errors that repeat

The first error is attributing all agitation in summer to the underlying disorder. The pre-test probability of heat-related illness rises sharply in patients with schizophrenia who use antipsychotics during a heat wave, and fever can go unnoticed when no one takes the temperature.

The second error is thinking the problem affects only older adults. The New York data and the review in young people show a clear risk in children and adolescents (Niu et al., 2023; Lai et al., 2026).

The third error is advising that medications be stopped because of the heat. The Medicare study shows risk associated with the drug classes, but it does not test withdrawal, and relapse is costly (Layton et al., 2020).

The fourth error is using a fixed temperature threshold. What counts is the heat relative to what the population is used to, as shown by the local percentiles used in the studies (Nori-Sarma et al., 2022; Corvetto et al., 2023).

The fifth error is ignoring cold. The review in older adults showed that low temperatures are also associated with worse mental health outcomes (Byun et al., 2024).

How NEXO helps train this reasoning

In NEXO, the case of the day is fictional, with a real clinical presentation and up to six progressive clues, and you propose the diagnosis by looking for the code in ICD-10.

The limits on using the game are described on the NEXO Economy page. If you research the teaching of clinical reasoning, the page for Researchers explains how to get in touch. Professionals who write or review cases find information under Curator and under Creators, and institutions can learn about the proposal on the partnerships page. Training differential diagnosis with clues and looking for the right ICD-10 code complete this practice.

Frequently asked questions

Does heat really increase psychiatric crises?

Yes, in population studies. Emergency visits and admissions for mental disorders rise on hot days in several countries, including Brazil. The effect is modest for each person, but large when added up across the population.

Which disorders seem most sensitive to heat?

The effect appears in anxiety, mood, substance use, schizophrenia, self-harm and behavioral disorders in childhood. Schizophrenia stands out in admissions and deaths in several studies.

Is there a link between heat and suicide?

The data show that suicide risk rises with temperature in many countries, including Brazilian cities. It is a population association, which justifies strengthening surveillance during hot periods, but it does not predict individual risk.

Should I stop antipsychotics in summer?

Not on your own. These medications are associated with a higher risk of heat-related illness, but stopping them can cause relapse. The way forward is surveillance, hydration, a cool environment and a plan agreed with the doctor.

Why are children affected?

They depend on adults to protect them from the heat and often express discomfort through behavior. In New York, the 6 to 11 age group had the largest increase in visits on hot days.

Take-home messages

• Heat increases visits and admissions for mental disorders.
• The effect reaches several categories, from anxiety to psychoses and substance use.
• Suicide risk follows temperature in many countries, including Brazil.
• Children and young people are also vulnerable, not only older adults.
• Anticholinergics, antipsychotics and diuretics increase the risk of heat illness.
• On a summer shift, psychiatric agitation calls for a measured temperature and a clinical assessment.

References

1. Baecker L, Iyengar U, Del Piccolo MC, et al. Impacts of extreme heat on mental health: Systematic review and qualitative investigation of the underpinning mechanisms. J Clim Chang Health. 2025. PMID 41646246.
2. Bundo M, de Schrijver E, Federspiel A, et al. Ambient temperature and mental health hospitalizations in Bern, Switzerland: A 45-year time-series study. PLoS One. 2021. PMID 34637463.
3. Byun G, Choi Y, Foo D, et al. Effects of ambient temperature on mental and neurological conditions in older adults: A systematic review and meta-analysis. Environ Int. 2024. PMID 39603080.
4. Corvetto JF, Federspiel A, Sewe MO, et al. Impact of heat on mental health emergency visits: a time series study from all public emergency centres, in Curitiba, Brazil. BMJ Open. 2023. PMID 38135317.
5. da Silva I, de Almeida DS, Hashimoto EM, et al. Risk assessment of temperature and air pollutants on hospitalizations for mental and behavioral disorders in Curitiba, Brazil. Environ Health. 2020. PMID 32631375.
6. Hansen A, Bi P, Nitschke M, et al. The effect of heat waves on mental health in a temperate Australian city. Environ Health Perspect. 2008. PMID 18941580.
7. Heo S, Lee W, Bell ML. Suicide and Associations with Air Pollution and Ambient Temperature: A Systematic Review and Meta-Analysis. Int J Environ Res Public Health. 2021. PMID 34300149.
8. Kim Y, Kim H, Gasparrini A, et al. Suicide and Ambient Temperature: A Multi-Country Multi-City Study. Environ Health Perspect. 2019. PMID 31769300.
9. Lai KY, Bauermeister S, Sarkar C. Associations of heat exposure with mental health and suicide in children and adolescents: a systematic review and meta-analysis. Npj Ment Health Res. 2026. PMID 41617837.
10. Layton JB, Li W, Yuan J, et al. Heatwaves, medications, and heat-related hospitalization in older Medicare beneficiaries with chronic conditions. PLoS One. 2020. PMID 33301532.
11. Lõhmus M. Possible Biological Mechanisms Linking Mental Health and Heat-A Contemplative Review. Int J Environ Res Public Health. 2018. PMID 30021956.
12. Niu L, Girma B, Liu B, et al. Temperature and mental health-related emergency department and hospital encounters among children, adolescents and young adults. Epidemiol Psychiatr Sci. 2023. PMID 37066768.
13. Nori-Sarma A, Sun S, Sun Y, et al. Association Between Ambient Heat and Risk of Emergency Department Visits for Mental Health Among US Adults, 2010 to 2019. JAMA Psychiatry. 2022. PMID 35195664.