Climate change and mental health

The year 2023 was the hottest ever recorded and included an unusually high number of extreme weather events, signs of a changing climate. This article describes how climate change can negatively affect mental health and suggests ways to mitigate these negative effects. Climate change can adversely affect mental health through acute extreme weather events, such as heat waves, droughts, floods, wildfires, and major storms and also through chronic changes such as increasing temperatures. Climate change may have indirect effects associated with displacement of homes and/or food insecurity; and increase anxiety associated with the perception of climate change. Clinicians should be aware of the mental health consequences of climate change to prepare for patients’ evolving needs.

Experiencing extreme weather events is associated with higher rates of anxiety, depression, post-traumatic stress disorder, suicidal ideation and suicide attempts, and substance use. Estimates suggest that 25–50% of those exposed to an acute extreme weather event will experience one of these negative mental health outcomes, most commonly anxiety, depression, or posttraumatic stress disorder (PTSD).¹ Effects may persist for months or even years after the event. For example, before Hurricane Katrina, a Category V hurricane that damaged New Orleans in August 2005, approximately 24% of 438 low-income mothers in a cohort study from New Orleans reported general psychological distress on a series of questionnaires. Within one year after Hurricane Katrina, 35% of the same sample reported general psychological distress and 12 years after the storm, the rate of reported general psychological stress in this sample was still 29%.² PTSD, in children, can be associated with smaller grey matter and hippocampal volume compared to healthy children unaffected by PTSD.³ The potential for extreme weather events to affect mental health depends in part on the magnitude of exposure and harm, prior exposure to traumatic events or economic stressors, and access to resources such as food, shelter, social support and medical and mental health care.⁴

The chronic effects of climate change, including higher ambient temperatures, significantly reduced or increased periods and intensity of precipitation, and rising sea levels, can impair mental health. Significant associations have been documented between high temperatures and increased psychiatric hospitalizations and suicide deaths.⁵ In a systematic review and meta-analysis, a 1° C increase in mean daily temperature was associated with a 1.7% increase in suicide deaths (n=113,523 across 5 studies). Among three studies with 111,794 people during a heatwave (daily temperature of at least 35° C for at least 3 consecutive days in some studies and > 27.5° C for at least 1 day in other studies), psychiatric hospitalizations or visits to a hospital due to mental health symptoms increased 9.7%.⁵ High temperatures may impair mood and cognitive functioning, and are associated with increased violence; some studies have suggested a 6% increase in homicide and a 7% increase in risk of major depressive disorder globally for every 1° C rise in temperature.⁶ There are multiple pathways for the social and neurological impacts of high temperatures, including an inflammatory brain response.⁶

Climate change also adversely affects economic wellbeing and increases rates of poverty and food insecurity.⁷ For example, job losses occur when agriculture workers lose employment due to weather-related crop damage or when extreme weather events disrupt businesses and infrastructure. Home values may decrease because of increased threat of flooding or wildfire, and insurance premiums may rise or property may become uninsurable. These changing economic circumstances, in turn, may require people to migrate if they cannot support themselves in a particular location or that location becomes uninhabitable due to climate-linked phenomena such as lack of adequate water supply or rising sea levels. Both economic insecurity and involuntary migration negatively affect mental health, particularly for young children.¹ Economic effects and displacement also disrupt communities and networks of social support, which could otherwise help mitigate the effects of climate change on negative mental health outcomes. Even people who are not directly affected may experience the severity and unpredictability of climate change as an existential threat that negatively affects wellbeing.⁸ Climate anxiety in particular has been linked to established measures of clinical anxiety and depression.⁹

The adverse effects of climate change are not distributed equally.¹ Current evidence is primarily from high-income countries, but factors associated with greater vulnerability to climate change include certain geographical locations (such as low-lying islands, coastlines, flood plains), female gender (due to factors associated with social roles and with childbearing; female gender is also an independent risk factor for anxiety disorders), lower socioeconomic status, either younger or older age, and preexisting mental health problems. Indigenous people are also more likely than non-indigenous people to be affected by climate change because they often live in areas that are vulnerable to climate change and have traditional cultural practices that are disrupted by a changing climate.³ In part because they are experiencing greater levels of warming, those living in the global south (e.g., countries in Africa, South America, the Caribbean, and parts of Asia) are already experiencing stronger adverse effects of climate change, though there has been little scientific investigation of the mental health effects of climate change in those regions.

The combined effects of climate change, economic instability, and poorer access to mental health care could worsen a mental health crisis in the global population of individuals who have these intersecting risk factors. Globally, clinicians should prepare for this by training to support their patients’ mental health needs during times of climate-related uncertainty about the future, for instance, when a patient’s home or job is at risk due to climate change (as described above). There is little documented evidence for therapies directed at improving mental health related to climate change. However, a recent pilot test of internet-delivered cognitive behavioral therapy (N = 60) found significant decrease after eight weeks in climate-change related distress among the treatment group as compared to the control group, with a moderate effect size (d = 0.79).¹⁰ Training in cognitive behavioral therapy may help prepare the mental health workforce to respond to increasing mental health needs due to climate change, including helping patients to engage in proactive problem solving about climate-related obstacles, reduce ineffective avoidance of changes that are necessary in their lives, and promoting assertive communication about need for support. Clinicians could incorporate measures of climate anxiety, such as the Climate Change Anxiety Scale⁸ into their practice in order to raise awareness about the prevalence of the climate impact on mental health. Clinicians should consider making referrals to behavioral health specialists (e.g. cognitive behavioral therapy for anxiety or depression) to support their patients whose mental health is threatened by coping with climate change.

Further scientific investigation is needed to more clearly delineate the effects of climate change on mental health as well as the factors that influence who experiences these effects, with a particular emphasis on data from low- and middle-income countries.³ Scientific evidence should inform strategies to improve the ability to regulate emotions in the face of the stress of climate change and address trauma-related distress linked to climate change. In addition to scientific research and clinical training, increased societal support for mental health is necessary to provide preventive and responsive mental health care that is culturally sensitive and available to all in the face of a changing climate.