Heatwaves affect our brains: why we become more tired and irritable in the heat

Heatwaves don't only affect our bodies — they also take a toll on our mental wellbeing. Recent studies show that as temperatures rise, people become more fatigued, more impulsive, and more irritable, while stress, conflict, and difficulty concentrating all intensify.

Research cited by the Italian publication Il Post has observed a higher frequency of workplace accidents, acts of violence, and aggressive episodes during heatwaves. Scientists caution, however, that high temperatures are an aggravating factor rather than the primary cause of these problems.

Why heat makes us more irritable

To maintain a normal internal temperature, the body works harder: blood vessels dilate to release heat through the skin, and the heart pumps more forcefully. This extra effort consumes more energy and can cause fatigue, exhaustion, and a lower tolerance for stress, according to the source cited.

Furthermore, heavy perspiration increases the risk of dehydration, which is associated with headaches, difficulty concentrating, and reduced attention. Sudden mood swings and heightened irritability may also occur.

Psychologists explain that people often confuse the physiological reactions produced by heat with actual emotions: an elevated heart rate and laboured breathing can be interpreted by the brain as signs of anger or anxiety, which amplifies the feeling of agitation.

Sleep among the most affected functions

Tropical nights, with persistently high temperatures, reduce both the duration and quality of sleep. Lack of rest impairs memory, attention, and decision-making ability, leaving people more impulsive the following day and less able to cope with stressful situations. According to specialists, the combination of excessive heat and insufficient sleep explains why everyday conflicts arise more readily during heatwaves.

Who is most vulnerable

Children and elderly people struggle more with extreme temperatures, as their bodies regulate heat less efficiently. Sensitivity to heatwaves also varies from person to person.

Some studies show that individuals with high levels of neuroticism — one of the five major personality traits studied in psychology — react more strongly to heat-related stress. Climate acclimatisation also plays a role: people who usually live in cooler regions may feel the effects of a heatwave more intensely than those accustomed to high temperatures.

Impact on mental health

Heatwaves can worsen symptoms in people already living with depression, anxiety, or other mental health conditions. Research conducted in the United States and Australia has shown that on extremely hot days, emergency department presentations for psychiatric disorders, depressive episodes, substance use, and self-harming behaviours increase.

An analysis published in 2023 in journals from The Lancet group estimated that hospital admissions for mental health problems rise by nearly 10% during heatwaves. The authors stress, however, that there is insufficient evidence to consider high temperatures a direct cause, given that social, economic, and medical factors are also at play.

Caution with medication during heatwaves

Specialists warn that certain medications, including some antidepressants, can alter the mechanisms by which the body regulates temperature and perspiration, potentially increasing the risk of dehydration and overheating.

People undergoing treatment should follow their doctor's recommendations and pay close attention to staying hydrated, avoiding prolonged exposure to the sun. Against the backdrop of climate change and increasingly frequent heatwaves, a growing number of experts believe that the effects of extreme temperatures on mental health will become an ever more pressing concern, alongside the already well-documented impact on the heart, lungs, and cardiovascular system.