The Effects of Climate Change on Mental Health

According to the National Oceanic and Atmospheric Association, last month was the hottest June on record. The world is in the midst of a punishing heat wave, and the temperature in Death Valley, California, could tie or set the record for the hottest temperature ever reliably measured on Earth.

Extreme heat causes serious and sometimes fatal effects on the human body. Less is known about how prolonged heat impacts our mental health. According to the American Psychiatric Association, extreme heat is associated with increases in irritability and symptoms of depression, along with an increase in suicides.

In addition to prolonged extreme heat, climate change is responsible for an increase in serious natural disasters such as hurricanes, flooding, and wildfires like the Canadian fires this summer. The research on the effects of climate change on physical health is abundant, but less research is available on how it affects our mental health. Here are some of the things we do know:

• Anxiety Disorders: In a British review published in the International Journal of Research and Public Health, researchers found that individuals in the United Kingdom who experienced storm or flood damage, reported a significant increase in anxiety, post-traumatic stress disorder, use of prescription drugs and alcohol. The authors reviewed 17 studies that investigated the effect of extreme weather events like floods and heat waves on the mental health of participants who lived through those events. They found the prevalence of post-traumatic stress disorder was 30 percent, much higher than the lifetime prevalence rate of 8 percent reported in the general population.
• Gender-Based Violence: A recent review in Lancet Planet Health reported the results of 41 studies that examined the effects of natural disasters such as flooding, hurricanes, and drought on gender-based violence in the communities that lived through the disasters. They found an increase in reported gender-based violence in most of the communities studied. One theory put forward is that living through extreme events could increase reporting and unmasking of pre-existing violence. Some victims felt they could no longer endure the abuse after living through extreme events. Another explanation advanced is that coming together as a community after an extreme event increases the visibility of violence. Existing social roles and norms combined with other forms of inequality can cause women and sexual minorities to be disproportionately vulnerable to extreme events. These findings are in line with other studies that report a general increase in violence in communities after natural disasters.

Several themes emerge in research that investigates an upsurge in violence after natural disasters. There is an increase in stressors that spark violence, such as trauma, mental health difficulties, financial insecurity, an increase in enabling environments due to an absence of policing, and a breakdown in health and support services. The impact of isolation was also evident during the lockdown during the recent COVID-19 pandemic. The incidence of domestic violence and child abuse rose dramatically both domestically and globally during that time.

• Suicide: Suicide is a major public health concern with more than 800,000 deaths each year worldwide. It is the second leading cause of death in young people 15 to 29 years of age. Past research has linked increases in environmental temperature with an increase in suicide rates. Last August, The French Institute for Health and Medical Research published a report stating that high temperatures coincide with increased suicide rates. The authors proposed that this relationship could be due to the effect of temperature on our body’s level of serotonin. Serotonin is one of our main neurotransmitters. Serotonin deficit has been linked to a number of psychiatric conditions such as depression and anxiety.

Another theory proposed by the Belgian Center for Suicide Prevention involved a change in social interactions during extremely warm days. Many people choose to stay indoors when the weather is very hot. This can lead to social isolation for those who are at risk for suicidal ideation.

Stanford researchers found a strong correlation between warm weather and increased suicides across the U.S. and Mexico. They compared historical temperature and suicide data across thousands of U.S. counties and Mexican municipalities over several decades. The team also analyzed the language in over half a billion Twitter updates or tweets to further determine whether hotter temperatures affect mental well-being. They analyzed, for example, whether tweets contain language such as “lonely,” “trapped,” or “suicidal” more often during hot spells. Their results indicated that there is strong evidence that hotter temperatures increase the use of depressive language on social media as well as suicide rates.

• Sleep disruptions Adequate sleep is critical to our overall health including mental health. Hot temperatures can lead to significant problems with sleep. For those without adequate cooling like air conditioning or fans, the process becomes even more difficult. Prolonged sleep deprivation can lead to memory loss and other cognitive deficits. Impaired sleep can lead to a manic episode for those with an underlying bipolar disorder. Aside from being critical to our overall health, sleep is a necessary component for mood regulation. Poor sleep has been suggested as one of the factors involved in a higher suicide rate during extremely hot weather.
• Dysregulation in neurotransmitters: Heat can decrease serotonin, one of our neurotransmitters. It is important in mood regulation and keeping aggressive impulses in check. Serotonin is an important messenger that sends signals between the skin and an area of the brain involved in temperature regulation. People with depression often have difficulties with this thermoregulation process. Interestingly, when these individuals take an antidepressant that raises the brain’s level of serotonin (SSRIs) the problems can be alleviated.

According to the Indian Journal of Occupational and Environmental Medicine, climate change is likely to impact our mental health in many ways. The imperative to mitigate greenhouse gases involves less reliance on fossil fuels and developing and using alternate efficient power sources.

This year has been the hottest on record and there is no reason to believe the trend will not continue. Knowing the impact that climate change has on mental health should encourage lawmakers to fund research into this area and to create the necessary infrastructure to treat what is already an increase in the incidence of mental illness and a lack of sufficient treatment options. In researching this topic, I learned about The Climate Psychiatry Alliance, a group of mental health providers who educate both the public and professionals about the crisis of climate change, particularly as it impacts mental health. One of its founders, Dr. Robin Cooper of the University of California San Francisco believes, “We have to start thinking about climate change as a mental health crisis. If we ignore climate change as a public health threat, we are abdicating our role as healthcare providers.”