The Effects of Climate Change on Mental Health

Background: All over the world, climate change is exerting negative and complex effects on human living conditions and health. In this narrative review, we summarize the current global evidence regarding the effects of climate change on mental health.

Methods: A systematic literature search concerning the direct effects of acute extreme weather events (floods, storms, fires) and chronic stresses (heat, drought) due to climate change, as well as the indirect effects of climate change (food insecurity, migration), on the diagnoses of mental disorders, psychological distress, and psychiatric emergency admissions was carried out in PubMed and PsychInfo, and supplemented by expert selection. 1017 studies were identified, and 128 were included.

Results: The heterogeneity of study methods does not permit any overall estimate of effect strength. The available evidence shows that traumatic experiences due to extreme weather events increase the risk of affective and anxiety disorders, especially the risk of post-traumatic stress disorder. Heat significantly increases the morbidity and mortality attributable to mental illness, as well as the frequency of psychiatric emergencies. Persistent stressors such as drought, food insecurity, and migration owing to climate change can also be major risk factors for mental illness.

Conclusion: The consequences of climate change are stress factors for mental health. Therefore, as global warming progresses, an increasing incidence and prevalence of mental illness is to be expected. Vulnerable groups, such as the (already) mentally ill, children, and adolescents, need to be protected. At the same time, there is a need for further systematic research on the mechanisms of action and effects of climate change on mental function.

Climate, the Earth’s ecosystems, their biodiversity, and human civilization are all closely linked. Climate change is man-made, the consequences of which exceed the capacity of the various ecosystems to adapt. The loss and damage caused (1) is becoming an increasingly palpable and visible threat to human health (2, 3).

Although it may not be possible to establish a clear causal relationship, climate change has nevertheless led to an increase in frequency and intensity of natural disasters and extreme weather events. These are having a most obvious impact on human health and are used in the scientific literature to operationalize climate change (2, 4). This overall situation is also associated with long-term changes to living conditions which can have a stressful impact on mental well-being (3).

In this narrative review, we summarize current global evidence of the direct and indirect effects of climate change on mental health, underlining available information about those particularly vulnerable groups such as children and adolescents.

Methods

Using the literature databases PubMed and PsycINFO, a systematic search was conducted for the direct effects (natural disasters, i.e., floods, storms, fires; extreme weather conditions, i.e., heat and drought) and indirect effects (climate-related migration, food insecurity) of climate change on mental health (ICD-10/DSM-5 diagnostic codes; mental distress; psychiatric hospital admissions). It was concluded on November 16, 2021.

Additional literature recommendations were formulated by a panel of experts from the German Association for Psychiatry and Psychotherapy, Psychosomatics and Neurology (DGPPN) on the subject of climate change and mental health (eMethods). The search included studies involving all human populations, worldwide. After removing any duplicates, a total of 1017 articles published between 2000 and 2021 were screened, leaving 128 articles for final inclusion (eFigure). A detailed description of the methodology used can be found in the eMethods.

eFigure

PRISMA flow diagram

Results

In the following, we will first present the evidence covering the direct effects on mental health of acute and chronic exposure to climate change, followed by their indirect effects. The Figure provides a schematic representation of the association between the effects of climate change and mental health. The results of the most important studies mentioned are presented in detail in eTables 1–3, while Tables 1 and 2 contain brief accounts. Preference is given to reports of systematic reviews and results of meta-analyses.

Figure

Schematic representation of the association between climate change and mental health

Table 1

Evidence of the direct effects of acute exposure to natural disasters on mental health

Table 2

Evidence of the direct effects of chronic exposure to extreme weather on mental health

Direct effects: Acute exposure

Floods

Climate change has led to an increase in flood events, which in turn are particularly associated with an increased prevalence of anxiety disorders, post-traumatic stress disorders (PTSD) as well as symptoms of depression (5, 6, 7, 8, 9).

A meta-analysis of the consequences of flooding in the United Kingdom showed that, six to 12 months after the extreme weather event of flooding, the point prevalence for PTSD was significantly increased in those affected in comparison with the lifetime prevalence in the general population (30.36% versus 7.4%) (5). Even three years after a flood disaster, the health-related quality of life of those directly affected by flooding is severely restricted in comparison with unaffected persons with regard to anxiety/depression (odds ratio [OR] = 4.30; 95% confidence interval [2,48; 7,72]) (10). The main predictors of developing a mental health condition after a flood disaster are socioeconomic vulnerability, long-term displacement (7), persistent material damage (9), and insurance-related problems (8) (eTable 1). The buffer effect of social support after a flood disaster is reduced by the severity of the impact of the floods (11). Vulnerable personal living conditions result in a greater risk of developing symptoms of depression (12). However, tourists who had been exposed to flooding and then returned to an unaffected home country also demonstrated long-term symptoms of PTSD, depending of the severity of their exposure (13, 14). Children and adolescents are particularly vulnerable (15). It is assumed that they have at their disposal fewer coping strategies after traumatic flood disasters and experience less self-efficacy (16). In particular, children prone to rumination have an increased risk of developing symptoms of depression after experiencing a flood (17).

Storms

Storms and tornadoes cause damage and destruction and, consequently, mental stress to patients with pre-existing mental disorders. They can also create new psychiatric disorders in previously healthy individuals (in particular anxiety-mood disorders, PTSD) (18, 19, 20, 21).

After hurricane Katrina in 2006 in New Orleans (USA), the 30-day prevalence of anxiety-mood disorders, including PTSD, rose to 49.1% in those directly affected (19). Hurricane-related post-traumatic stress symptoms are still measurable up to 12 years after the event (Table 1, eTable 1) (20, 22).

The likelihood of posttraumatic symptoms and depression increases with the severity of exposure, even more so in the case of physical injury, death or serious injury to household members, low income, and storm-related property damage (22). Other risk factors for depression and post-traumatic symptoms include loss of social support and socioeconomic decline (23, 24, 25, 26).

The expansion of deserts worldwide has resulted in more frequent adverse health effects from dust storms, the consequences of which are similar to those of fine particulate air pollution (27).

Even prenatal exposure to hurricanes can result in increased anxiety and elevated cortisol levels (111.11 versus 76.49 pg/mg, p <0.001) in early childhood (28). Adolescents and young adults with family dysfunction and other traumatic experiences are particularly vulnerable (25, 29). Between 20.3% and 49.4% of health-care first responders after a hurricane reach, or even exceed, the clinical cut-off score for PTSD (30, 31). The mentally ill are also particularly at risk from destroyed supply chains and infrastructure: Following hurricane Katrina in the USA, the successful treatment completion rate among discharged patients with a comorbid mental disorder declined significantly from 36.8% to 18.7% (32).

Fires

A recent review shows high prevalences of PTSD (15.6–60%), depression, and generalized anxiety in adults between the post-acute phase (three months) and up to years after a wildfire or bushfire (33) (Table 1, eTable 1). The principle risk factor is the fire trauma itself, i.e., a high level of exposure to a fire has a stronger effect on mental health than a low level of exposure (34).

An increased rate of mental disorders (PTSD during the subacute phase after a wildfire: 92 %, depression after 18 months: 33.3 %, anxiety disorder after 18 months: 27 %) was also found after wildfires and bushfires in the child population of the mentioned review (33). An Australian longitudinal study showed that experiencing bushfires in childhood can be most stressful. In adulthood, 20 years later, the prevalence of lifetime anxiety disorder is greater than in an unaffected control group (21.5% versus 16%, relative risk [RR] = 1.37 [1.05; 1.78), p <0.05). Lifetime and point prevalence rates after 20 years for depression and eating disorders were not significantly increased as a result of experiencing a fire in childhood (35). If other traumatic experiences are added to the fire event during further life, however, there is an increased prevalence of lifetime PTSD for children (7.8% versus 5.8%, RR = 1.80 [1.11; 2.93], p <0.05), but not without this cumulative effect (35).

The negative income development in areas after a fire disaster can lead to increased violence, especially against women, resulting in negative effects on their mental health several years after the fire disaster (36). A systematic review of the consequences for the health of firefighters confronted with wildland fires came to the result that 10 to 20% of responders reported post-traumatic stress symptoms (37). Other vulnerable groups are elderly people with dementia, inhabitants of rural communities, and indigenous populations (38).

Direct effects: Chronic exposure

Heat

Heat is associated with increased morbidity, a surge in psychiatric emergencies, and a significantly increased risk of dying from mental disorders: Thus, the morbidity of mood disorders, organic mental disorders, schizophrenia, and neurotic and anxiety disorders increases with high outdoor temperatures and during heatwaves (39, 40). For example, the risk for mental morbidity during heatwaves was increased by 6.4% (39) (Table 2, eTable 2).

Heat is associated with increasing numbers of psychiatric emergencies and (emergency) admissions to psychiatric hospitals (e1, e2). There is a notable positive association between heat and hospital admissions, especially for psychoses (39) and dementia (e3). The availability of outpatient healthcare services and of green open spaces, on the other hand, appears to be a protective factor (e4).

Mental disorders are also among the most important risk factors for heat-related deaths, tripling (OR = 3.61) the risk of dying during a heatwave (39, e5, e6). In extreme heat, the use of alcohol, medications, and illegal drugs is associated with an increased risk of mortality. A systematic review also shows in 15 of 17 studies a positive association between higher temperatures and the incidence of suicides (RR = 1.04–1.37) (eTable 2) (e7). In the week after moderate and extreme heat, there is an approximately twofold increased (cumulative) risk of mortality from suicide (RR = 1.8 and 2.16, respectively) (e8). Until the beginning of a national suicide prevention program in Finland, temperature variations explained more than 60% of suicide variance (e9). For several decades in North America, suicide rates were associated with the average monthly temperature, increasing by 0.7% (USA) and 2.1% (Mexico) for a 1° C temperature increase (e10).

There are comparatively few studies available on children and adolescents. However, a deterioration of mental health and increase in emergency department contacts for mental disorders with rising temperatures was also demonstrated for this young group (e11, e12, e13, e14).

eBox 1

PubMed search terms

eBox 2

PsycINFO search terms

Drought

People who are, or were, affected by drought have a 26% higher likelihood (OR = 1.26; p <0.01) of mental problems than those not affected (13.3% versus 10.8%) (e15). The direct and indirect, and especially economical, effects of drought promote the development of depression and anxiety disorders as well as increased alcohol and substance use (e16). Drought is also associated with increased suicide rates. Australian long-term data revealed that, with increased values of the drought index, there was a 15% increased risk of suicide for rural middle-aged men (e17).

As a result of malnutrition and loss of livelihood, as well as due to economic factors (e16), droughts have the effect of potentially chronic psychological stress factors (e19), especially for those working in agriculture (e18). In addition, there is a potential for increased family tension, emotional stress, and domestic or intimate-partner violence (e16, e20, e21).

Indirect effects

Apart from the direct effects of environmental pollution and natural disasters or extreme weather events, climate change is also associated with indirect and systemically mediated health effects (e22).

Food insecurity

Not only can drought be the cause of food shortage and the destruction of, or alteration to, agricultural areas (e16), but the nutritional content and quality of cereal crops may also decrease, resulting in the development of deficiency symptoms (e23).

Poor nutrition can impair cognition and also cause mental symptoms, such as fatigue, lethargy, depression, manias, and psychoses (e23, e24). Food insecurity in British families, for example, was associated with maternal depression, psychotic disorders, domestic violence, and behavioral problems in children (e25), see eTable 3 for details.

Malnutrition in children can impair (neuronal) development, resulting in an increased risk of mental illnesses such as depression and attention deficit hyperactivity disorder (e23). Other vulnerable groups include women and the elderly in whom a particularly strong dose-dependent relationship is evident between food insecurity and distress (e26, e27) as well as mental disorders (e28, e29).

Climate-related migration

Economic and institutional crises can also arise from climate change. The destabilization of states, groups, and regions induced by climate change can lead to violent conflicts and wars, acting as a driver of environmentally induced migration (e30).

The forced, permanent displacement of people increases the probability of their developing anxiety and affective disorders (e31, e32, e33, e34). Negative experiences and difficulties in the adjustment process after migration also lower self-esteem, promote depressive symptoms, and increase the risk of suicide (e35). Refugees also have a higher risk of developing psychotic disorders than non-refugee migrants (e36).

Children and adolescents in particular suffer from migration-related stressors. In a systematic review, Kien and colleagues (2019) report of point prevalences of between 19% and 52.7% for PTSD, 10.3 to 32.8% for depression, 8.7 to 31.6 % for anxiety disorders, and 19.8 to 35% for emotional and behavioral problems (e37) (eTable 3).

Flight and migration are considerable psychological stressors (e22, e30, e38). Apart from those stress factors which initially forced people to migrate, their experience of migration itself can be characterized by numerous material and psychological losses. Stress, separation and loneliness, loss of identity, no sense of belonging, lack of social values and networks with no support and socioeconomic resources are significant risk factors for mental health (e16, e30, e31, e39). Children can be separated from their parents during flight (e40) and are particularly at risk of experiencing violence during (e41, e42), as well as after, flight (e43).

An uncertain residence status, with its associated restricted rights, and difficulties with integration are additional stress factors during migration to a foreign country (e44, e45). At the same time, there are also barriers to accessing psychiatric health care (e45, e46).

Environmental migration often involves moving from rural to urban areas, thus often depriving those affected of an environment with green spaces as a protective factor and putting a strain on mental health with additional city-specific risk factors, such as air pollution and noise (e31, e47). Added to this, there is often deterioration in living and working conditions (e48).

Discussion

These results indicate that, with progressive global warming, a greater mental health burden on the general population and an increased need for care for mental disorders are to be expected. Heat makes many mental disorders worse, with subsequent increases in morbidity and mortality. Natural disasters raise the prevalence of, above all, PTSD, depression and anxiety disorders of those affected.

The effects of climate change on health are unequally distributed (e49, e50, e51, e52). Increased geographical exposure, the underlying health status, and limited adaptive and coping capacities can increase the vulnerability of individuals or populations. Mentally ill people as well as children and adolescents belong to those groups of people who are particularly vulnerable to the effects of climate change (e50).

Climate change-related disasters can destroy infrastructures of the health care system and, at the same time, raise demands on health care (e55). Germany too is affected by an increasing number of natural disasters and weather extremes; a progressive disease burden of mental health is to be expected as a result of climate change (e53, e54).

There is further need for research on the newly developed syndromes brought on by climate change, including “solastalgia” (emotional reaction to the destruction of the environment) and “climate anxiety” (expectation of future involvement) (e56, e57).

Adaptations of the care systems to the anticipated increased psychiatric and psychotherapeutic needs and to the expanded spectrum of diagnoses resulting from climate change appear to be an urgent necessity.

Limitations

It should be added by way of caveat that studies looking at the mental health effects of climate change cannot be randomized and only minimally controlled. As a result, their level of evidence is usually low to moderate. Furthermore, the quantitative summary of evidence is difficult in that operationalizing climate change effects has so far been very heterogeneous and often indirect. There is a need for studies with comparable methodology and coverage of mental disorders (according to DSM-5/ICD-10) as well as specific mechanisms of action.

Conclusions

These available studies demonstrate that the consequences of climate change are stress factors for mental health. Therefore, as global warming progresses, an increasing incidence and prevalence of mental illnesses are to be expected. The slowing down of climate change by reducing CO2 emissions and measures to also counteract the long-term effects of climate change (for example, green areas in towns, heat protection in hospitals) are urgently needed. Health resilience programs at individual and societal levels are needed to at least attempt to address the impending stresses on humanity’s mental health from climate change (e55).

Acknowledgement

We would like to thank all the members of the DGPPN task force “Climate change and mental health” who provided us with their literature collection and expertise for this review: Prof. Dr. med. Mazda Adli, Dr. med. Barbara Bornheimer, Dr. med. Lasse Brandt, Prof. Dr. med. Dr. phil. René Hurlemann, Julie Holzhausen, Dr. med. Sebastian Karl, PD Dr. med. Hans Knoblauch, Prof. Dr. med. Christoph Nikendei, Sandy Pistol, Prof. Dr. med. Steffi G. Riedel-Heller, Dr. med. Nina Marsh, Anna-Karina Schomburg M. A., Dr. med. Kirsten Shukla, Dr. med. Dr. PH Stefan Weinmann, Dipl.-Psych. Franziska Welzel.

Conflict of interest statement
Prof. Meyer-Lindenberg has taken on paid and unpaid work for the foundation “Hector Stiftung II”, for Janssen-Cilag GmbH, MedinCell, Sage Therapeutics, Anna-Monika Stiftung, the German Association for Psychiatry,Psychotherapy and Psychosomatics, the German Research Foundation, the Permanent Senate Commission on Key Questions in Clinical Research, the Heinrich Lanz Center, Leopoldina, and the European College of Neuropsychopharmacology.

The other authors confirm that no conflict of interest exists.

Manuscript received on 30 June 2022, revised version accepted on
07 December 2022.

Translated from the original German by Dr. Grahame Larkin, MD

Corresponding author
Prof. Dr. med. Andreas Meyer-Lindenberg

Central Institute of Mental Health (CIMH)

J 5, 68159 Mannheim

Cite this as:
Walinski A, Sander J, Gerlinger G, Clemens V, Meyer-Lindenberg A, Heinz A: The effects of climate change on mental health.
Dtsch Arztebl Int 2023; 120: 117–24. DOI: 10.3238/arztebl.m2022.0403

►Supplementary material

eReferences, eMethods, eTables, eFigure, eBoxes:
www.aerzteblatt-international.de/m2022.0403

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This article has been certified by the North Rhine Academy for Continuing Medical Educatio. Participation in the CME certification program is possible only over the internet: cme.aerzteblatt.de. The deadline for submission is 23 February 2024.

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