Climate ChangeEnvironment

The impact of heat on our mental health

Every 1°C temperature, deaths related to mental health reasons increase by 2.2%

During the summer of 2022, throughout Europe, heat waves caused at least 61 premature deaths. Italy is the most affected country with 18,000 deaths. Even for the less fragile, high temperatures can be disabling, increasing the number of hours lost and causing a drop in productivity. Beyond the physical effects, which are the most obvious, high temperatures also have a psychological impact. What is the connection between heat and mental health?

The link between heat and mental health

Although it is a topic that is rarely addressed except in the specialist literature, the link between heat and mental health is now established by a long series of scientific studies. And the effects cover a pretty wide range. An increase in temperatures has been linked to the worsening of symptoms of those already suffering from mental illness. Heat waves, but also other extreme climatic events, cause an increase in depressive symptoms in those who are depressed and make those suffering from generalized anxiety disorder more anxious.

Exceptionally high temperatures are also linked to an increase in suicides and suicide attempts. Just as the increase in relative humidity is causally linked to these gestures. A study published in Nature in 2021 and based on data from 60 countries concluded that the categories most at risk of suicide in extreme heat and exceptional humidity values are young people and women. These two factors, temperature and humidity, can also lead to an increase in manic episodes in people with bipolar disorder.

A study that analysed about 50 scientific papers published in recent years has calculated that for every 1°C temperature, mortality linked to mental health factors increases by 2.2%.

Effects on non-pathological subjects

The heat completes mental health even in subjects who are not affected by any pathology. Higher temperatures negatively affect our ability to think. A study conducted in 2016 showed that sleeping with air conditioning allows you to be much more careful and focused during the day. Two groups of college students took the same test for two weeks. Half of them were in rooms without air conditioning, with a temperature around 26 ºC. The other half had air conditioners and slept with 21 ºC fixed. The latter had clearly better performances than their colleagues.

Another study, in 2021, found that beyond a certain temperature our parasympathetic system starts to work worse. When activated, the parasympathetic system determines a relaxation of the muscles and a reduction of emotional tension. Thermal stress, on the other hand, is associated with a slowing down of the areas of the brain that preside over the solution of complex cognitive tasks.

Also hot and irritability are directly related. And not only in personal relations face to face. An analysis of 4 billion tweets between 2014 and 2020 reveals that when the temperature rises above 21,
increases the frequency of discriminatory and aggressive messages exchanged online. This is true only in some geographical areas, but above 30 degrees the increase in online hate speech applies to all latitudes.

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