Heatwaves have a huge impact on our physical and mental health. Doctors usually dread them, as emergency rooms quickly fill up with patients suffering from dehydration, delirium and fainting. Recent studies suggest at least a 10% rise in hospital emergency room visits on days when temperatures reach or exceed the top 5% of the normal temperature range for a given location.
Soaring temperatures can also make symptoms worse in those with mental health conditions. Heatwaves – as well as other weather events such as floods and fires – have been linked to a rise in depressive symptoms in people with depression, and a rise in anxiety symptoms in those with generalised anxiety disorder – a disorder where people feel anxious most of the time.
There is also a link between daily high temperature and suicide and suicide attempts. And, roughly speaking, for every 1℃ increase in monthly average temperature, mental health-related deaths increase by 2.2%. Spikes in relative humidity also result in a higher occurrence of suicide.
Humidity and temperature – both of which are changing as a result of human-induced climate change – have been causally linked to a rise in manic episodes in people with bipolar disorder. This state of the illness causes significant harm and can result in hospitalisation for psychosis and thoughts of suicide.
Further problems are posed by the fact that the effectiveness of important drugs used to treat psychiatric illness can be reduced by the effects of heat. We know that many drugs increase the risk of heat-related death, for example, antipsychotics, which can suppress thirst resulting in people becoming dehydrated. Some drugs will work differently depending on the body temperature and how dehydrated the person is, such as lithium, a very potent and widely used mood-stabiliser, frequently prescribed for people with bipolar disorder.