Climate change is likely to have major mental health impacts worldwide, yet there is currently a dearth of research in this important area, write Lisa Page and Louise Howard of the Institute of Psychiatry at Kings College London, UK. In an editorial in the journal Psychological Medicine, they argue that this situation needs to be urgently addressed 'so that mental health policymakers can plan for the impact of climate change on mental health'. There is a growing body of research into the health impacts of climate change, with some estimating that it is already causing over 150,000 deaths a year - a figure that is likely to rise over the coming decades. However, although there is now some recognition that climate change will affect mental health, the authors note that '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'. According to Drs Page and Howard, the effects of climate change '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'. For example, natural disasters are predicted to increase as a result of climate change. Mental health problems such as post-traumatic stress disorder, major depression and other disorders are common in the aftermath of disasters, natural or otherwise. Furthermore, as the case of Hurricane Katrina in the US demonstrated, '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,' the researchers point out. Heat waves are also expected to take a greater toll on the mentally ill, as psychotropic medicines and substance misuse are both risk factors for heat-related death. 'In addition, maladaptive coping mechanisms and poor-quality housing are likely to confer further vulnerability on people with mental health problems,' the authors note. Finally, there is 'preliminary evidence' that suicide levels may increase once a certain temperature threshold is crossed. Many infectious diseases are expected to become more common as the climate warms, and this is also likely to affect mental health, the researchers warn. Cases of psychological distress, anxiety and traumatic stress have all been documented in both infected patients and the wider public during disease outbreaks. Rising sea levels will force millions of people living in coastal areas to move. Mass exoduses are also likely in areas stricken by floods or droughts or other extreme conditions. 'Mass migration will undoubtedly lead to an increased burden of mental illness in affected populations,' the researchers caution, pointing out that conflicts are another possible driver of migration. Another problem is that mental health services in many low- and middle-income countries are already woefully inadequate. Drs Page and Howard fear that these services are 'unlikely to be prioritised should further economic collapse occur secondary to climate change'. The researchers conclude that mental health professionals urgently need to engage in research on this subject. 'Collaboration with other disciplines will be crucial,' the authors write. '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.' Says Dr Page: 'Climate change is assuming centre stage with the [...] UN conference in Copenhagen. While delegates will discuss the effects of climate change and possible responses by the international governments, we fear that the effects of climate change on mental health will be largely ignored, posing a tremendous risk to the mental health of millions of people in the not-too-distant future.'