When the heat hits more than the body
„I’m just permanently irritable in this heat.“ – „I’ve been sleeping badly for weeks and I don’t know why.“ – „Don’t make such a fuss, it’s only warm.“
Switzerland had a marked heatwave in June 2026 with new June records, and another one followed in July – warning level 3 south of the Alps, peaks between 31 and 35 degrees in the north, and nights that barely dropped below 20 degrees. We talk about the circulation as a matter of course. About the mind, hardly at all. Yet research has produced a surprising amount of new material on exactly that in recent months.
The new evidence: July 2026
On 10 July 2026, Nature Health published the first large multi-country study on the subject. A team led by Yuming Guo and Shanshan Li at Monash University in Australia analysed more than 2.6 million warm-season hospital admissions – 852 locations across Brazil, Canada, Chile and New Zealand, covering 2000 to 2019.
The result: sustained extreme heat was associated with a statistically significant rise in admissions for mental and behavioural disorders. The key word is sustained – not the single hot afternoon, but heat that doesn’t let up for days. Older adults and people in sparsely populated areas were hit hardest.
Important context: these are hospital data from four countries, not Swiss figures, and they describe associations, not proven causes. But the direction is clear – and it fits what smaller studies have been showing for years.
Why heat weighs on the mood
There is no mysterious mechanism. There are several very sober ones that add up.
Sleep goes first. In 2017, Nick Obradovich and colleagues linked the responses of around 765’000 survey participants with night-time temperatures in Science Advances. The finding: when night-time temperatures rise 1 degree above normal, that adds roughly three extra nights of insufficient sleep per 100 people per month. The effect was strongest among older people and those on low incomes – in other words, the people who cannot simply cool their home. And poor sleep hits precisely what we need most in the heat: emotion regulation, patience, concentration. More on this in the article Sleep and mental health.
The body runs continuously. Thermoregulation costs energy. A review in PLOS Climate describes how heat affects sleep, stress hormones and neurotransmitter balance at the same time – with a correspondingly greater risk of deterioration for people who already live with a mental illness.
Medication can slow the cooling down. Various psychotropic drugs – antipsychotics, tricyclic antidepressants or lithium, for example – interfere with sweating, circulation or fluid balance. That is no reason to panic, and certainly no reason to stop taking anything on your own. It is a good reason to raise the topic with your doctor before the height of summer.
The serious part
Two findings belong here, uncomfortable as they are.
Marshall Burke and colleagues found in Nature Climate Change in 2018 that a one-degree rise in average monthly temperature went along with suicide rates around 0.7 per cent higher in the United States and around 2.1 per cent higher in Mexico. The study has not gone unchallenged in the field, and it says nothing about individual people – it describes shifts at population level.
In February 2026, PLOS Mental Health added an analysis of 11’684 crisis line risk assessments from a helpline in Louisiana (2019–2023). The hotter the nights, the more frequent suicide-related help-seeking – markedly more frequent at very high night-time temperatures than in the normal range. The authors also trace the pathways: sleep problems, impulsivity, isolation, unmet basic needs.
🔴 Important: If you are feeling very bad, don’t wait for cooler weather. In Switzerland you can reach Die Dargebotene Hand around the clock on 143, young people can call 147, and in an emergency 144.
What actually helps in hot weeks
Most of it is unspectacular – and effective for exactly that reason.
- Protect sleep first. Ventilate at night and early morning, black the place out consistently during the day, keep windows shut when it’s warmer outside than in. The coolest room becomes the bedroom, not the nicest one.
- Adapt the day to the heat, not the other way round. Demanding conversations, decisions and focused work belong in the cool morning hours. The afternoon is for routine.
- Lower your expectations – deliberately. At 34 degrees you are not less capable because you have lost the knack. Your body is already at work. Getting less done is the correct response, not a character flaw.
- Drink, and think about electrolytes – banal, but the most common blind spot among people who work with focus and forget to drink.
- Read irritability as a signal. If you notice you are being short with people: that is often heat plus lack of sleep, not your relationship with the person in front of you. Saying it out loud defuses a surprising amount.
- Look out for the vulnerable. Calling the neighbour who lives alone is one of the most effective heat measures there is – see also Loneliness: the underestimated public health problem.
🟢 Tip: In hot weeks, deliberately schedule short breaks somewhere cool instead of pushing on until nothing works any more. How much even a few minutes achieve is described in Micro-breaks: small time-outs. And the early walk in the woods beats the midday walk in the city twice over – see Nature as therapy.
Conclusion
Heat is not only a question of circulation and sunscreen. The new body of evidence – 2.6 million hospital admissions across four countries, sleep data from hundreds of thousands, four years of crisis calls – points consistently in one direction: sustained heat weighs on the mind, above all through sleep and above all for those who are already carrying a load. That is not weakness and not imagination. It is an environmental factor you are allowed to plan for, just as you plan for winter tyres.
Are you having a hard time getting through these weeks?
In coaching we look together at what is really exhausting you – the heat, the circumstances, or something that has been sitting below the surface for longer – and how to rebuild your everyday life so it carries you.
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