Earlier this summer, I wrote about “summer SAD,” the very real worsening of mood, anxiety, agitation, and sleep that some people experience during the hottest and brightest months of the year.
After this weekend, I think the conversation needs to go further. Temperatures in the Sacramento area have exceeded 100°F, and over the past several days I have seen multiple previously stable patients experience abrupt and clinically significant psychiatric destabilization.
One patient with a history of a severe perinatal mood disorder, who had been stable enough to begin a very gradual medication taper, suddenly went two nights without sleeping and required an increase in medication. Another patient with bipolar I disorder experienced worsening mixed symptoms. A third experienced a marked increase in severe depression and suicidal thinking. My phone and email have been unusually busy as I have worked with patients and their families to stabilize symptoms safely in the outpatient setting, while continually assessing whether emergency evaluation or a higher level of care is needed.
These are clinical observations, not proof that the heat directly caused each episode. Psychiatric symptoms are complex, and correlation is not causation. But the clustering was difficult to ignore, and the emerging research suggests that extreme heat may be an important and underrecognized psychiatric stressor.
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A 2025 ecological momentary assessment study followed thousands of adults with depression or bipolar disorder. Each 1°C increase in mean temperature over the preceding two weeks was associated with a small but measurable increase in manic symptoms. The relationship varied according to season and each person’s usual level of heat exposure.
A Canadian study of more than 30,000 adults with schizophrenia found a statistically significant increase in hospital admissions for psychosis three days after exposure to unusually high temperatures. A large U.S. study examining nearly 3.5 million mental health-related emergency department visits found that extreme-heat days were associated with higher rates of visits for mood disorders, anxiety and stress-related conditions, psychotic disorders, substance use disorders, and self-harm.
The mechanism is probably not one single thing. Heat can disrupt sleep, increase physical discomfort and irritability, worsen dehydration, alter routines, reduce exercise and time outdoors, and increase social isolation. Some psychiatric medications can also affect sweating, temperature regulation, thirst, blood pressure, or hydration status.
Sleep disruption may be particularly dangerous for people vulnerable to mania, psychosis, or severe mood episodes. The large U.S. emergency department study specifically identified disrupted sleep as one plausible pathway through which heat may worsen psychiatric illness.
This does not mean that every difficult summer day is a psychiatric emergency. It does mean that extreme heat should be treated as a meaningful clinical variable, not merely an inconvenience.
During heat waves, people with serious mood or psychotic disorders may need to be especially vigilant about:
- Protecting sleep and keeping the bedroom cool
- Maintaining hydration and regular meals
- Taking medications consistently
- Avoiding alcohol, cannabis, stimulants, and excessive caffeine
- Monitoring for reduced need for sleep, escalating agitation, racing thoughts, impulsivity, paranoia, withdrawal, hopelessness, or suicidal thinking
- Asking family members to speak up when they notice a meaningful change
- Contacting the treating clinician early rather than waiting for symptoms to become unmanageable
For clinicians, it may be time to consider extreme-heat planning alongside other relapse-prevention strategies, particularly for patients with bipolar disorder, psychotic disorders, severe depression, suicidality, or a history of rapid deterioration after sleep loss. Winter is not the only season capable of affecting psychiatric health. Sometimes the dangerous season is the one filled with relentless sunlight, disrupted sleep, isolation indoors, and triple-digit heat.
Heat is not just uncomfortable. For some vulnerable patients, it may be destabilizing.
If you or someone you know is experiencing suicidal thoughts, psychosis, severe agitation, an inability to sleep with worsening psychiatric symptoms, or an inability to remain safe, call or text 988 for immediate crisis support. Call 911 or go to the nearest emergency room if there is an immediate danger, a medical emergency, or an inability to maintain safety.
Carrie Friedman is a dual board-certified psychiatric and family nurse practitioner and the founder of Brain Garden Psychiatry in California. She integrates evidence-based psychopharmacology with functional and integrative psychiatry, emphasizing root-cause approaches that connect neuro-nutrition and gut–brain science, metabolic psychiatry, immunology, endocrinology, and mind–body lifestyle medicine. Carrie’s clinical focus bridges conventional psychiatry with holistic strategies to support mental health through nutrition, physiology, and sustainable lifestyle interventions. Her professional writing explores topics such as functional medicine, autism, provider well-being, and medical ethics.
