Introduction
In recent years public health scientists have begun to document and predict the health impacts of climate change. This has gained momentum in the past year with the publication of several influential papers (Frumkin & McMichael, Reference Frumkin and McMichael2008; Costello et al. Reference Costello, Abbas, Allen, Ball, Bell, Bellamy, Friel, Groce, Johnson, Kett, Lee, Levy, Maslin, McCoy, McGuire, Montgomery, Napier, Pagel, Patel, de Oliveira, Redclift, Rees, Rogger, Scott, Stephenson, Twigg, Wolff and Patterson2009; Wiley et al. Reference Wiley, Gostin, Wiley and Gostin2009). In 2007, the Fourth Intergovernmental Panel on Climate Change (IPCC) assessment report was published and included a chapter on the health effects of climate change (Confalonieri et al. Reference Confalonieri, Menne, Akhtar, Ebi, Hauengue, Kovats, Revich, Woodward, Parry, Canziani, Palutikof, van der Linden and Hanson2007); the report clearly documents the evidence for a wide range of adverse health outcomes consequent on climate change and alludes to the fact that many important outcomes will be psychological. Mechanisms for the health impacts of climate change include altered patterns of infectious disease, injuries from severe weather events, food and water scarcity, and population displacement (Confalonieri et al. Reference Confalonieri, Menne, Akhtar, Ebi, Hauengue, Kovats, Revich, Woodward, Parry, Canziani, Palutikof, van der Linden and Hanson2007; Costello et al. Reference Costello, Abbas, Allen, Ball, Bell, Bellamy, Friel, Groce, Johnson, Kett, Lee, Levy, Maslin, McCoy, McGuire, Montgomery, Napier, Pagel, Patel, de Oliveira, Redclift, Rees, Rogger, Scott, Stephenson, Twigg, Wolff and Patterson2009). Meanwhile, others have pointed to the increased global health disparities that climate change will bring, as the poorest countries are likely to suffer the greatest health impacts (McMichael et al. Reference McMichael, Friel, Nyong and Corvalan2008). By the beginning of this decade it was estimated that in excess of 150 000 deaths per year were already occurring as a result of climate change (Patz et al. Reference Patz, Campbell-Lendrum, Holloway and Foley2005) and this number is expected to greatly expand as we approach the middle of the century (Confalonieri et al. Reference Confalonieri, Menne, Akhtar, Ebi, Hauengue, Kovats, Revich, Woodward, Parry, Canziani, Palutikof, van der Linden and Hanson2007). Planning to protect public health in relation to climate change is therefore ongoing on the international stage (WHO, 2009), although the economic and environmental impacts seem to be the prime focus of governments' interests, rather than the health impacts.
Despite this recent activity and the broad recognition that the mental health effects of climate change will be significant, such effects are mostly discussed in vague terms and rarely by those actively involved in mental health research or policy. Mental health is unlikely to feature on the Copenhagen agenda. In this editorial we argue that some of the most important health consequences of climate change will be on mental health and we consider the mechanisms by which these may occur. We also suggest that this is an opportune time for those involved in mental health research to become involved in the debate.
Direct effects
Natural disasters, such as floods, cyclones and droughts, are predicted to increase as a consequence of climate change (IFRC, 2009). This is largely due to the greater likelihood of extreme meteorological events in the years ahead. Adverse psychiatric outcomes are well documented in the aftermath of (natural) disaster (Norris et al. Reference Norris, Friedman, Watson, Byrne, Diaz and Kaniasty2002) and include, among others, post-traumatic stress disorder (Galea et al. Reference Galea, Nandi and Vlahov2005), major depression (Marshall et al. Reference Marshall, Schell, Elliott, Rayburn and Jaycox2007) and somatoform disorders (van den Berg et al. Reference van den Berg, Grievink, Yzermans and Lebret2005). Although enhancing disaster preparedness has become an international priority in recent years, the psychological implications of disasters are often under-recognized (Costello et al. Reference Costello, Abbas, Allen, Ball, Bell, Bellamy, Friel, Groce, Johnson, Kett, Lee, Levy, Maslin, McCoy, McGuire, Montgomery, Napier, Pagel, Patel, de Oliveira, Redclift, Rees, Rogger, Scott, Stephenson, Twigg, Wolff and Patterson2009). Hurricane Katrina is a striking example of how disaster-related mental health problems can become intractable, even in Western industrialized countries (Kessler et al. Reference Kessler, Galea, Gruber, Sampson, Ursano and Wessely2008). Hurricane Katrina also illustrated how medical and psychiatric care can dramatically diminish for those with pre-existing mental illness in the period following a disaster, at a time when it is needed most (Weisler et al. Reference Weisler, Barbee and Townsend2006). The needs of people with chronic mental illness have often been overlooked following disaster in favour of trauma-focused psychological interventions and yet the mentally ill occupy multiple vulnerabilities for increased mortality and morbidity at such times. Fortunately, recent guidance now specifically advises humanitarian agencies on how to better care for people with chronic mental illness in the mass emergency situation (IASC, 2007).
As global temperatures increase, heat waves will become more common, last longer and be more severe (Meehl & Tebaldi, Reference Meehl and Tebaldi2004). It is now well recognized that, above a certain threshold, there is a relationship between increasing temperature and increasing mortality (Basu & Samet, Reference Basu and Samet2002). This heat effect is particularly pronounced during heat wave episodes, with an estimated 70 000 dying as a result of the European heat wave of summer 2003 (Robine et al. Reference Robine, Cheung, Le Roy, Van Oyen, Griffiths, Michel and Herrmann2008). There are a variety of reasons to believe that people with mental illness are particularly vulnerable to heat-related death. For example, psychotropic medication is a risk factor for heat-related death (Bouchama & Knochel, Reference Bouchama and Knochel2002), as is pre-existing respiratory and cardiovascular disease (Basu & Samet, Reference Basu and Samet2002) and substance misuse (Marzuk et al. Reference Marzuk, Tardiff, Leon, Hirsch, Potera, Iqbal, Nock and Hartwell1998), all of which are highly prevalent in people with serious mental illness. In addition, maladaptive coping mechanisms and poor quality housing are likely to confer further vulnerability on people with mental health problems (Kovats & Ebi, Reference Kovats and Ebi2006). Finally, there is preliminary evidence that death by suicide may increase above a certain temperature threshold (Page et al. Reference Page, Hajat and Kovats2007; Qi et al. Reference Qi, Tong and Hu2009), suggesting that psychological mechanisms such as impulsivity and aggression could be triggered during periods of hot weather. At present, research and policy interest is focused on the vulnerability to heat-related death of people with chronic physical illness and the elderly, but such interest has not been extended to the mentally ill.
In addition, several infectious diseases are predicted to become more common as a consequence of global warming (e.g. malaria, dengue fever, schistosomiasis, tick-borne encephalitis; see Costello et al. Reference Costello, Abbas, Allen, Ball, Bell, Bellamy, Friel, Groce, Johnson, Kett, Lee, Levy, Maslin, McCoy, McGuire, Montgomery, Napier, Pagel, Patel, de Oliveira, Redclift, Rees, Rogger, Scott, Stephenson, Twigg, Wolff and Patterson2009). Adverse impacts such as psychological distress, anxiety and traumatic stress resulting from emerging infectious disease outbreaks have previously been documented in infected patients (De Roo et al. Reference De Roo, Ado, Rose, Guimard, Fonck and Colebunders1998), staff (Maunder, Reference Maunder2004) and the general public (Leung et al. Reference Leung, Lai-Ming, Chan, Sai-Yin, Bacon-Shone, Choy, Hedley, Tai-Hing and Fielding2005). Therefore, should outbreaks become more widespread, an increased burden of mental health problems is likely.
Not all of the mental health effects of climate change will necessarily be negative. Akin to postulated physical health benefits of fewer cold-related winter deaths and shorter influenza seasons, it is possible that warmer average temperatures could benefit some people with mental illness. At present, this remains speculative, as this possibility has not been investigated.
Indirect effects
Indirect consequences of climate change, such as migration and economic collapse, are potential drivers of adverse health outcomes (Costello et al. Reference Costello, Abbas, Allen, Ball, Bell, Bellamy, Friel, Groce, Johnson, Kett, Lee, Levy, Maslin, McCoy, McGuire, Montgomery, Napier, Pagel, Patel, de Oliveira, Redclift, Rees, Rogger, Scott, Stephenson, Twigg, Wolff and Patterson2009). Low-lying coastal areas will become uninhabitable as coastlines disappear; this is particularly concerning as 13 of the world's largest 20 cities are situated on the coast. Coastal areas in poor countries will be the worst affected. Coastal change and other manifestations of climate change, such as increased flooding events in some areas and water scarcity in others, are predicted to lead to forced mass migration. Conflicts may also increase in number and constitute another cause of population displacement (Costello et al. Reference Costello, Abbas, Allen, Ball, Bell, Bellamy, Friel, Groce, Johnson, Kett, Lee, Levy, Maslin, McCoy, McGuire, Montgomery, Napier, Pagel, Patel, de Oliveira, Redclift, Rees, Rogger, Scott, Stephenson, Twigg, Wolff and Patterson2009). Mass migration will undoubtedly lead to an increased burden of mental illness in affected populations. The vulnerability of those with pre-existing serious mental illness during complex emergencies has recently been highlighted (Jones et al. Reference Jones, Asare, El Masri, Mohanraj, Sherief and van Ommeren2009).
Urbanization (the drift of populations from rural to urban areas) is predicted to continue for the foreseeable future, particularly as droughts and floods threaten traditional rural economies. Urban drift in conjunction with population growth means that the urban population in low- and middle-income countries is predicted to increase from 2.3 billion in 2005 to 4 billion by 2030 (Costello et al. Reference Costello, Abbas, Allen, Ball, Bell, Bellamy, Friel, Groce, Johnson, Kett, Lee, Levy, Maslin, McCoy, McGuire, Montgomery, Napier, Pagel, Patel, de Oliveira, Redclift, Rees, Rogger, Scott, Stephenson, Twigg, Wolff and Patterson2009). Urbanization brings with it some potential health advantages, mainly due to increased opportunities for work and economies of proximity and scale (for example by bringing more of the population closer to major health infrastructure so that access to mental health services is improved). However, urbanicity in developed countries is associated with an increased incidence of schizophrenia (March et al. Reference March, Hatch, Morgan, Kirkbride, Bresnahan, Fearon and Susser2008), and concerns have also been expressed about the negative impact of urbanization on mental health in low- and middle-income countries (Trivedi et al. Reference Trivedi, Sareen and Dhyani2008).
Mental health provision in many low- and middle-income countries is already hugely inadequate (Jacob et al. Reference Jacob, Sharan, Mirza, Garrido-Cumbrera, Seedat, Mari, Sreenivas and Saxena2007) and is unlikely to be prioritized should further economic collapse occur secondary to climate change. Capacity to support the infrastructure needed to train and supervise mental health workers will deteriorate if mental health budgets are not protected. Finally, some have postulated that the knowledge of man-made climate change could in itself have adverse effects on individual psychological well-being (Fritze et al. Reference Fritze, Blashki, Burke and Wiseman2008).
Research challenges
Mental health professionals in clinical, research and policy arenas need to realize that their expertise is crucial to further understanding of the health effects of climate change. Given the likely scope and geographical range across which health effects will be felt, the methodological challenges of studying the themes outlined above are considerable. Collaboration with other disciplines will be crucial; we may need to work with climatologists, geographers, environmental epidemiologists, urban planners, economists, modellers and development specialists to plan and execute meaningful research on these topics. Recent initiatives by funding bodies such as the National Institutes of Health in the USA and the Wellcome Trust in the UK indicate that there is a willingness to fund health research related to climate change. This will be important to inform future mental health policy priorities as climate change progresses.
Conclusion
We suggest that climate change has the potential to have significant negative effects on global mental health. These effects will be felt most by those with pre-existing serious mental illness, but there is also likely to be an increase in the overall burden of mental disorder worldwide. In this editorial we have attempted to explore the mechanisms by which these effects might occur and highlight the vulnerability of those living in the poorest countries. Research is almost entirely lacking in this area, a situation we would urge be addressed so that mental health policy makers can plan for the impact of climate change on mental health.
Declaration of Interest
L.A.P. and L.M.H. are recipients of grants from the MRC (General Practice Research Database access to data scheme 08_002R) and BUPA Foundation (TBF-08-012) entitled: ‘Temperature related deaths in people with serious mental illness’.
Acknowledgements
We are very grateful for the constructive comments of two anonymous reviewers. L.M.H. is affiliated with the National Institute for Health Research, ‘Biomedical Research Centre for Mental Health’, Institute of Psychiatry and South London and Maudsley NHS Foundation Trust.
