Climate change and mental health: unequal effects, but not by chance

The COVID-19 pandemic has shown that minoritised and indigenous communities are at heightened risk from combined social and ecological shocks, including adverse weather events and pandemics, owing to vulnerability resulting from pre-existing factors such as discrimination, exclusion, poverty, land dispossession and malnutrition.^{Reference Zavaleta-Cortijo, Ford, Arotoma-Rojas, Lwasa, Lancha-Rucoba and García4} There are also inequalities in exposure to ecological hazards. A study on associations between air pollution and neighbourhood characteristics in England and The Netherlands found higher concentrations in the most deprived 20% of neighbourhoods in England, with higher concentrations in both countries in neighbourhoods with >20% non-White populations, after adjustment for urbanisation and other variables.^{Reference Fecht, Fischer, Fortunato, Hoek, de Hoogh and Marra5}

On a global scale, there is increasing recognition that climate change is compounding many health inequities and undermining pre-existing support structures which protect against poor mental health.^{Reference Ford, King, Galappaththi, Pearce, McDowell and Harper6} The climate crisis has been called a racist crisis, reflecting both its disproportionate effects on Black communities and people of colour globally, as well as its evident unequal effects within countries.^{Reference Sealey-Huggins7,Reference Pellow8} Following Hurricane Katrina, for example, Black New Orleanians faced greater stress than their White counterparts, even after adjustment for demographics, parental status, evacuation timing, home damage and job status; income had no clear effect.^{Reference Elliott and Pais9} There was a similar pattern for post-traumatic stress disorder, which was partly but not fully explained by greater baseline mental distress.^{Reference Alexander, Ali, McDevitt-Murphy, Forde, Stockton and Read10}

In recent years, campaigns for international action on climate change have highlighted how unjust social and economic systems, including legacies of colonialism, structural racism, and other exclusionary forces such as sexism and ableism at all levels shape vulnerability to the effects of climate change on mental and physical health. We contend, as argued by Leon Sealey-Huggins and colleagues (2018), that ‘we can only properly understand the harm being wrought by weather events and climate change by directly connecting it to broader social and political processes, of which structural racism is a central part’.^{Reference Sealey-Huggins7}

Future research must further clarify the mechanisms as a result of which people with severe mental illness are more vulnerable to the adverse effects of climate change. This should include a recognition of closely interwoven vulnerabilities due to social exclusion, stigma and direct consequences of their illness or medications, as well as the effects of unequal distribution of resources at local, national and international levels, all of which affect people's and communities’ capacities to cope and adapt.

Intersections between urban health inequalities and climate change effects

Cities are the places where most people live globally – 56% of the global population as of 2018^{Reference Desa11} – and are the places where people are most exposed to the adverse effects of climate change. For example, the urban heat island effect means that higher temperatures are experienced in urban areas than in more rural ones nearby, and access to places for people to cool off in, such as shady green spaces or waterways, is often more limited. The health effects of rising exposure to high temperatures are not only physical but have also been associated with increased risks of mental ill health^{Reference Hansen, Bi, Nitschke, Ryan, Pisaniello and Tucker12} and with suicide.^{Reference Page, Hajat and Kovats13}

Cities are also a key focus for research into mental health inequalities, particularly in relation to differences in urban versus rural rates of schizophrenia. The spatial distributions of other mental health outcomes such as suicide and self-injury are less clear cut, suggesting a greater need to further understand the influence of sociocultural and environmental characteristics of particular neighbourhoods.^{Reference McCulloch, Philip and Carstairs14} One example of this is how qualitative methods have begun to unpack the paradoxically low rates of direct self-harm in highly deprived areas in London.^{Reference Polling, Woodhead, Harwood, Hotopf and Hatch15}

People in cities often experience the greatest exposure to some of the key contributors to climate change, including air pollution from fossil fuels and degradation of green space. Further, increased exposure to poor-quality air and green spaces often mirrors and compounds pre-existing socioeconomic inequalities. Evidence on the lifelong effects of air pollution on mental health outcomes such as depression continues to emerge.^{Reference Bakolis, Hammoud, Stewart, Beevers, Dajnak and MacCrimmon16,Reference Braithwaite, Zhang, Kirkbride James, Osborn David and Hayes Joseph17} Exposure to air pollution and traffic noise are similarly unequal for different neighbourhoods with regard to both socioeconomic status and ethnicity, with those least likely to own a car often most likely to live in traffic-clogged and polluted areas.^{Reference Barnes, Chatterton and Longhurst18} At the same time, good access to urban nature can help to partially mitigate the harmful effects of socioeconomic inequalities.^{Reference Turrell, Haynes, Wilson and Giles-Corti19}

Further, there has been greater awareness of the urgent need for more urban green space^{Reference Kleinschroth and Kowarik20} and a recognition of strong disparities in access to green space in European cities.^{Reference Wüstemann, Kalisch and Kolbe21} Access to green space has been linked with reduced depression risk,^{Reference Cohen-Cline, Turkheimer and Duncan22,Reference Reklaitiene, Grazuleviciene, Dedele, Virviciute, Vensloviene and Tamosiunas23} and there is increasing recognition that social factors affecting both availability^{Reference Schüle, Hilz, Dreger and Bolte24} and levels of use^{Reference Haeffner, Jackson-Smith, Buchert and Risley25} seem to mediate the mental health effects of green and blue spaces such as parks, forests, rivers and beaches.

There is increasing evidence of biologically plausible explanations of associations between urban environmental exposures and mental health. These include the effects of traffic and air population exposure on neurodevelopmental pathways in children,^{Reference Costa, Chang and Cole26} neuroinflammation across the life course,^{Reference Braithwaite, Zhang, Kirkbride James, Osborn David and Hayes Joseph17} and changes in arousal and stress responses associated with time spent in green space.^{Reference Hedblom, Gunnarsson, Iravani, Knez, Schaefer and Thorsson27} Proposed mechanisms through which the green space's benefits may be manifest include a shift in attention, promoting curiosity, social networks, group cooperation and physical activity. However, methodological and interpretation challenges remain, for example, in understanding the importance of confounding factors such as noise pollution and general neighbourhood deprivation.^{Reference Braithwaite, Zhang, Kirkbride James, Osborn David and Hayes Joseph17} Limited studies have translated these observations into robust evidence for improved mental health.^{Reference Bhui28}

There is also a lack of research from low- and middle-income countries (LMICs) on the effects of climate change on mental health. This is urgently needed to inform policy action in these contexts. In LMIC contexts, forced migration due to climate change – with the destination locations often being cities – is a significant challenge, and studies have highlighted that dislocation from one's home compromises emotional well-being related to happiness, life satisfaction, optimism for the future and spiritual contentment, even despite well-intentioned relocation programmes focused on material compensation and livelihood re-establishment.^{Reference Snodgrass, Upadhyay, Debnath and Lacy29}

Challenges in conceptualising complexity

For mental health, ‘the risks and impacts of climate change … are already rapidly accelerating, resulting in a number of direct, indirect, and overarching effects that disproportionally affect those who are most marginalised’.^{Reference Hayes, Blashki, Wiseman, Burke and Reifels30} Our ability to fully appreciate and act on these vulnerabilities has been constrained by complexity on multiple levels, from the geographic scale to the interrelated nature of the underlying causal mechanisms.

These constraints have limited research into the effects of climate change on mental health, to date. Quantitative approaches have tended to focus mostly on proximate causes, which can obscure important structural and political drivers of the distribution of mental health effects of climate-related heatwaves, floods, wildfires and droughts.^{Reference McMichael31} Studies which have found associations between heat and mental health outcomes such as suicide have also cautioned about the difficulties of ascertaining causal effects using an ecological study design.^{Reference Page, Hajat and Kovats13}

Berry et al (2018) proposed that a systems approach that accounts for interrelated and interdependent factors, forming a complex whole, is important for future research thinking and leadership around climate change and mental health.^{Reference Berry, Waite, Dear, Capon and Murray32} We argue that this approach should also accommodate a structural and intersectional understanding of pre-existing inequalities in mental health. This may come from approaches which address broader inter-penetrative global socioeconomic processes such as globalisation,^{Reference Bhavsar, Zhang and Bhugra33} and the syndemics model of health that focuses on ‘interacting, co-present or sequential diseases and the social and environmental factors that promote and enhance the negative effects of disease interaction’.^{Reference Singer, Bulled, Ostrach and Mendenhall34}

The role of psychiatry in understanding and addressing climate change

In 2015, our Australasian colleagues^{Reference Every-Palmer, McBride, Berry and Menkes35} proposed the ‘CARM’ approach – to collaborate, advocate, research (and educate) and mitigate – as a framework for psychiatrists to join with a growing number of medical entities to act on climate change. We have proposed our recommendations within this same framework (Box 1), and with the emphasis that interventions need to be ‘coordinated and rooted in active hope’ to tackle the problem in a holistic and effective way.^{Reference Hayes, Blashki, Wiseman, Burke and Reifels30} Alongside growing recognition that we should practice psychiatry more sustainably,^{Reference Maughan and Davison36} we should acknowledge it as our professional and ethical responsibility to address the environmental, social and economic determinants of mental illness.^{Reference Every-Palmer, McBride, Berry and Menkes35}

About the authors

Shuo Zhang is a Core Psychiatry Trainee at South London and the Maudsley NHS Trust, London, UK; Isobel Braithwaite is an Academic Clinical Fellow in Public Health and ST4 Public Health Registrar at UCL Institute of Health Informatics, University College London, London. UK; Vishal Bhavsar is a Women's Mental Health and Violence Reduction and Consultant Psychiatrist at Lambeth Council and the Department of Health Services and Population Research, Institute of Psychiatry, Psychology and Neuroscience (IOPPN), King's College London and the South London and Maudsley NHS Foundation Trust, London, UK; and Jayati Das-Munshi is a Clinician Scientist & Honorary Consultant Psychiatrist at the Department of Psychological Medicine, IOPPN, King's College London & South London and the Maudsley NHS Trust, London. UK.