Heat waves and the mentally ill

To the Editor

Scott Henderson and Mulder (2015) encourage us to take a sceptical approach to claims that climate change presents a threat to world mental health. They call for data to be acquired before formulating an appropriate response. There are existing data relating to clear threats to the health of the mentally ill. This is strongest for the ‘very elderly’ about whom they suggest ‘very little’ has been written.

The authors concentrate on the literature examining the psychological consequences of discrete disasters. Climate change is not a discrete disaster. It is instead likely to be a collage of unfolding disasters. Certainly, it is difficult to predict the mental health consequences of these.

Heat waves are becoming more frequent and more severe with climate change. This is accepted by the relevant scientific body to a probability of ‘very likely’ (>90% chance) (Intergovernmental Panel on Climate Change [IPCC], 2014). Such levels of probability are rare in psychiatric literature.

It is not difficult to provide the data requested in relation to the direct health effects of heat waves on the mentally ill. Mortality increases during heat waves. The Russian heat wave of 2010 was associated with 55,000 increased deaths. Heat waves such as Chicago 1995, Europe 2003 and Victoria 2009 have shown increases in mortality rates. The Victorian heat wave review (Department of Health & Human Services, Victorian Government, 2009) concluded, ‘The elderly and the very elderly have been found … especially at risk’. Deaths directly related to heat, heatstroke, hyperthermia and dehydration increased massively. For those aged over 95, the risk was doubled. Of the 14,729 extra deaths in the European heat wave of 2003, 11,731 were over 75. A study of south German nursing home residents showed the elderly (especially those over 90) were most at risk. There were more than 400 extra deaths during the 2003 heat wave among the 95,808 residents. One study found that risk of death was increased in patients with a history of psychiatric admission in over 65s during heat wave days in Italy. Another established an association in people aged over 70 in the European heat wave of 2003 between antidepressants (adjusted odds ratio [aOR] 1.71) and antipsychotics (aOR 2.09). Overall risk of death was increased 30% for those taking any psychotropic drug.

Combining these mortality estimates and the projected increase in the frequency, duration and severity of heat waves, it is reasonable to conclude that many people with mental health issues will succumb. The elderly mentally ill are most at risk. Prevention is possible.

It is likely that if these scenarios unfold as predicted, the resources required to collect data and treat mental health issues will have been transferred elsewhere.