Various scientific research, such as those conducted by Harvard TH Chan School of Public Health or the analyzes published on The Lancet Planetary Healthdemonstrate that hyperthermia and thermal stress compromise the efficiency of our central nervous system. But what exactly do excessive temperatures harm? The heat specifically affects ours complex cognitive functionsor the working memorythesustained attentionThe problem solving and the ability to make sensible decisions, as well as having effects on mental health.
The biological mechanism of heat on the brain: thermoregulation and cognitive fatigue
Our body constantly works to maintain thermal homeostasis, i.e. a stable internal body temperature around 36.5°C. When the environmental temperature exceeds the tolerance threshold, the central nervous system activates the processes of thermoregulation.
The main mechanism consists of peripheral vasodilation: the body diverts blood flow and energy resources towards the skin to promote heat dispersion through sweating. This hemodynamic redistribution, however, involves a temporary reduction in optimal blood flow to the brain.
One of the most authoritative studies on the subject, published in 2018 in PLOS Medicine by researchers from the Harvard TH Chan School of Public Health, monitored a group of young adults residing in dormitories without air conditioning, with average internal temperatures of around 26°C. On dog days, subjects showed:
- A significant increase in reaction times in cognitive tests.
- A greater percentage of errors in calculation tasks and logic compared to those who resided in air-conditioned environments.
Those who suffer the greatest deficit are the so-called complex executive functions: working memory, sustained attention and problem solving ability. This clinical picture is further exacerbated by sleep deprivation and disturbed night rest, typical of tropical nights. Furthermore, research conducted on animal models indicates that thermal stress alters the synthesis of serotonina fundamental neurotransmitter not only for mood regulation, but also for brain thermoregulation centers.
Heat waves, irritability and aggressive behavior
The association between rising temperatures and an increase in impulsive behavior is a phenomenon that has been observed from an epidemiological point of view. An extensive review published in The Lancet Planetary Health summarized data from different areas of the world, highlighting significant trends:
- Increase in crimeseach increment of 5°C of daily temperature is associated with an increase in 4.5% of crimes of a sexual nature in the immediately following days.
- Physical assaults: in Japan there has been a constant growth in ambulance transports due to attacks coinciding with heat peaks.
It is important to specify that we are talking about statistical correlations and not of a direct and automatic cause-effect relationship: the social, economic and cultural factors of each territory play a fundamental role in mitigating or amplifying these behaviors.
However, biology tells us that extreme heat is in effect a stress factor for the organism, which responds by increasing the production of cortisol (the stress hormone). This hormonal spike drastically lowers ours tolerance threshold at the frustrationpushing us to more immediate and less filtered emotional reactions cerebral cortexwhich is the area of the brain responsible for reasoning and self-control.
The impact on the mental health and vulnerability of young people: psychiatry studies
If for healthy people the effects of heat are limited to temporary lapses in attention or mood swings, the impact becomes critical for those who already suffer from psychiatric disorders. In fact, during temperature peaks, emergency rooms record a constant increase in admissions for acute psychiatric crises.
Data collected during the historic 2021 heat wave in Canada revealed that people affected by schizophrenia had a mortality risk three times higher compared to the general population. This strong vulnerability depends both on the characteristics of the pathology and on the effect of some drugs that interfere with the body’s ability to sweat and regulate its temperature.
A very serious and recent piece of data, published on June 24, 2026 in the American Journal of Psychiatry, concerns younger people. The study shows that, for every degree increase in the average monthly temperature, the suicide rate among 15 and 24 years old increases by approximately 3%: an increase that is more than double that observed in adults. This evidence suggests that the brain of young people, being still developing, may be much more sensitive and vulnerable to the effects of environmental thermal stress.
Long-term projections: what will happen by 2100?
The effects of the heat do not only concern individual emergency days. A Chinese study published in 2024 in Ecotoxicology and Environmental Safety followed over 53,000 people for eight years, showing that prolonged and repeated exposure to high temperatures is associated with a more rapid decline in cognitive abilities over time.
By cross-referencing these data with climate change models, the projections would indicate a worrying scenario for public health: if temperatures continue to rise at current rates, the average cognitive functions of the global population could suffer a decline including between 5% and 7% by 2100.
The scientific data available to us therefore demonstrates that global warming and the intensification of heat waves are not only a threat to the environment or the economy, but represent a direct risk to our mental health, our reasoning abilities and our psychological well-being.
