Increased suicides, disrupted treatment, worry... heat does not help good mental health

"It's scorching hot. Enough to drive a man mad" : these words conclude a classic fantasy story, August Heat by British author WF Harvey, which ends with the narrator's probable murder.

They illustrate how heat remains associated in the collective imagination with mental instability, while France, and more broadly Europe, have been hit for several days by an early heatwave.

"It generates anxiety, it generates cancellations of appointments which can be detrimental, it generates more loneliness..." summarizes psychiatrist Bernard Granger, who practices in Paris at the Cochin hospital, to AFP.

While the psychiatrist reports that he has not yet noticed any marked change in his consultations in recent days, this is not the case everywhere.

Also in Paris, the Sainte-Anne psychiatric emergency department reported to AFP that an "unusual number" of patients were waiting to be seen on Tuesday, without being able to make a formal link to the high temperatures.

However, these have been accumulating with increasing frequency in recent years, against a backdrop of global warming, which makes it essential to examine their specific effects on mental health.

The data on this subject remains fragmentary , while the effect of heat is now very well documented for a number of pathologies: cardiovascular, respiratory, etc.

"Much remains unknown about the mental health implications of rising global temperatures," summarized the authors of a study published in 2023 in the Lancet Planetary Health , which provides one of the best overviews of current knowledge on the subject.

Increase in suicides

Heat, they note, can theoretically affect the mind in various ways: it disrupts physiological mechanisms such as serotonin production, it impairs sleep - crucial for good psychological balance - it encourages alcohol consumption...

But what is the reality? The authors compiled around twenty preliminary studies to conclude that high temperatures have a real, but moderate, effect on various indicators.

Thus, the studies "point to a link between rising temperatures and suicides," they note, even if "they are very heterogeneous in their methodologies and their results."

And, they note, heat waves appear to be associated with an increase in emergency room visits: around 10% . A level which, while moderate in itself, can put a heavy strain on already strained services, particularly during the summer.

The Lancet Planetary Health study also does not take into account a recent large-scale study carried out in Australia and published in the spring of 2025 in the journal Nature Climate Change. It confirmed a "growing impact" of extreme heat on mental health , although it is still difficult to assess in detail.

Above all, beyond the effect of the heatwave on the general population, AFP sources called for vigilance for patients already being monitored.

Certain behavioral disorders can indeed hinder proper compliance with preventive measures such as regular hydration, as Dr. Granger points out.

Above all, heat can disrupt the proper intake of drug treatments , such as lithium, which is used in particular for bipolar disorders.

"During extreme heat, there is a risk of dehydration which exposes people treated with lithium to the risk of overdose," psychiatrist Frank Bellivier, ministerial delegate for mental health, explained to AFP, as mental health has been declared a major national cause in France for 2025.

For him, the priority public health message, on the psychiatric side, is therefore to call on patients to hydrate particularly well and to have a blood test at the slightest symptom of an overdose : tremors, nausea, confusion, etc.