Sixty-five million Americans (one in five) take mental health medications, and the number is rising. The most common medications that doctors prescribe for their patients are for anxiety and depression. While climate change may cause more people to take mental health medication, climate change and extreme heat may make those medications work less well. 

Medications may not work as effectively when stored at higher temperatures, as could happen when the earth gets hotter. Often, pharmacies keep medications at low temperatures to prevent this from happening, but pharmacies may not always be able to keep things cool. Furthermore, hotter weather and dehydration both make it more likely for these drugs to cause potentially dangerous side effects when people take them.

Depending on the number of medications and types of medications that someone is taking, the likelihood of potentially dangerous side effects changes considerably.

People with serious mental illness such as schizophrenia, schizoaffective disorder, or bipolar disorder, as well as people who are on more than one medication, are at a high risk of worsened side effects in hot weather. There is evidence that people with schizophrenia, even without medicines, already have difficulty regulating their body temperatures and are at higher risk for heat-related death, so adding the effect that medicine has to raise body temperature can make the risks of taking them even worse. 

Climate change, in addition to causing worsened side effects, may also make getting medication more difficult. The creation, transportation, and delivery of medications may be disrupted. And of course people who don’t have medical insurance, or good enough medical insurance, or who otherwise have difficulty getting mental health care, are at higher risk. 

People who are taking medicine that leaves their body more quickly, and people with serious mental illness, may be in the most danger of having new symptoms and illness if they stop being able to get their medicine in a climate disaster, even if they were previously in a stable mental condition. 

When patients become sick, it affects their ability to get their medications and become well. People with schizophrenia, bipolar disorder, or dementia are more likely to have problems making their way to the pharmacy when they are not doing well. People who take certain medications for anxiety such as alprazolam (Xanax), lorazepam (Ativan), and clonazepam (Klonipin) may go into life-threatening withdrawal.

Given that hotter weather makes some medications less effective, and that extreme weather makes delivery, transportation, and creation of medications more challenging, people with mental illness may experience a worsening of their illness or even life-threatening side effects. 

Studying heat’s effect on mental health medications alone is difficult, if not impossible, as heat itself has many effects on mental health in and of itself. It is likely that the effect of heat on medications adds to increased patient suffering, emergency room visits, psychiatric and medical hospital stays, and strain on the system of mental healthcare.

Multiple classes of medications are affected by extreme heat and dehydration.

• Hotter body temperatures can occur for people who take antipsychotic medications (used for schizophrenia, bipolar disorder, and other conditions) such as olanzapine (Zyprexa), risperidone (Risperdal), or haloperidol (Haldol). 
  
• High body temperatures and overheating can also occur when people take other types of mental health medication. These medications treat multiple kinds of mental illness, and include:
  
  • Antidepressants used for depression, anxiety, and/or chronic pain such as mirtazapine (Remeron), amitriptyline (Elavil, Endep, Vanatrip), and nortriptyline (Pamelor, Aventyl HCl).
    
  • Anxiety medications such as hydroxyzine (Vistaril, Atarax, Rezine).
    
  • Specific over-the-counter sleep medications and diphenhydramine used for sleep (found in Benadryl, Allermax, Banophen, Diphedryl, Sominex, Aleve PM, and others) can be risky, or even lethal, in extreme heat.
    
• Several antidepressants, some sleep medications such as trazodone (Desyrel, Oleptro) or doxepin, and pain medications called opioids can cause increased sweating, which makes dehydration more likely.
  
• Dehydration can raise drug levels of lithium and mood stabilizers leading to illness and side effects.
  
  • People who use substances such as alcohol and MDMA, or ecstasy, are already more likely to become dehydrated .
    
• Patients taking certain anxiety medications need to be careful that they could withdraw and even die if they cannot get their medication in extreme weather. These medications include alprazolam (Xanax, Niravam), lorazepam (Ativan, Loreev XR), and clonazepam (Klonipin).

• People who take or prescribe mental health medications should be careful and weigh the risks and benefits of each medication, especially in hotter areas. Here’s information on how to store medications to ensure they do not break down in hotter weather. Medications requiring extra care include insulin, nitroglycerin, inhaler medications, birth control and other hormone-based medication, test strips (eg, pregnancy tests or diabetic strips).

• Given that the amount of medication in the blood may not stay steady in hotter weather, physicians may choose to check laboratory tests for drug levels or kidney function. One example of a drug level that should be checked is lithium. 

• Physicians and people taking mental health medication should also look out for side effects such as tardive dyskinesia (a condition with abnormal involuntary muscular movements), tremor, unsteadiness, or sleepiness. People taking these medications should learn the specific side effects associated with each of their medications and let their physician know if they experience symptoms. 

• It may make sense for some people on mental health medications to have a larger amount of medication on hand, especially those with schizophrenia, bipolar disorder, or anxiety (specifically those on medications where they can withdraw). This is often a risk-and-benefit decision. Having large amounts of medication could be risky for people who suffer from substance abuse or who have attempted suicide by overdose, depending on the medication and circumstances.

• Physicians should discuss having emergency substance withdrawal kits with patients taking certain medications or who have substance use disorders.

Heat and Medications – Guidance for Clinicians, published July 17, 2024 by CDC (U.S. Centers for Disease Control and Prevention), with content from National Center for Environmental Health (NCEH)

National Institute of Mental Health patient information, including side effects of common mental health medications

How to keep your medicines safe during hot weather, published on July 8, 2026 in The Conversation by Dipa Kamdar.

How extreme heat can hinder effectiveness of pregnancy tests, some contraception, published on August 23, 2023 in The 19th by Shefali Luthra

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Published: September 22, 2022
Updated: September 30, 2026
Author: Tova Fuller, MS MD PhD, Psychiatrist
Editor: Rei Takver