If you’ve ever wondered why a hot day wipes you out more than it does the person next to you, your medicine drawer might have the answer. Doctors say some of the most commonly prescribed drugs for depression, anxiety, ADHD, and high blood pressure, quietly mess with the body’s ability to cool itself down.And with heatwaves getting longer and more intense every year, that’s a problem more people are running into without realising it.Here are the details that you need to know about your meds.
Why antidepressants leave you more exposed to heat
The brain has a built-in thermostat called the hypothalamus, and it’s responsible for the small automatic things that keep us from overheating, sweating, slowing down, adjusting our metabolism.“This area of the brain gets us to reduce our activity, to sweat more, to reduce our metabolism – all beneficial adaptations to heat,” Robert Feder, a retired psychiatrist based in New Hampshire and member of the steering committee for the Medical Society Consortium on Climate and Health told BBC.Common antidepressants like sertraline, fluoxetine, escitalopram, and venlafaxine work by boosting serotonin levels in the brain. The trouble is, too much serotonin around the hypothalamus can throw that cooling system off balance, causing excessive sweating in roughly one in five people who take these drugs. Sweat more than usual, and you lose water and salts faster, a rough combination when it’s already scorching outside.Older-style antidepressants, known as tricyclics, cause the opposite issue for some people: they block a chemical called acetylcholine, which can shut sweating down instead of ramping it up. Either way too much sweat or too little, the body’s natural cooling gets disrupted.
When several medications stack up
Antipsychotic medications, used for conditions like schizophrenia and bipolar disorder, add another layer of risk, they block dopamine in a way that stops the body’s cooling response altogether, and studies have tied their use to higher death rates during past heatwaves.ADHD stimulants like Ritalin bring their own twist: they raise the body’s internal heat production and narrow blood vessels, while also masking the feeling of overexertion, so people may not notice they’re overheating until it’s serious.
Blood pressure and heart drugs carry risks too
It’s not only psychiatric medication. Diuretics and blood pressure drugs known as ACE (angiotensin-converting enzyme) inhibitors and ARB (angiotensin II receptor blockers). It can throw off the body’s electrolyte balance and even blunt the sensation of thirst, meaning people don’t drink enough even when they badly need to.“With that combined impact, you can get really severely dehydrated to the point where it increases your risk of renal failure, a heart attack, or one of many other severe organ impacts,” says Logan Harper, a family physician and assistant fellowship director of the University of Colorado Anschutz’s climate and health programme.Beta blockers, another heart medication, restrict blood flow to the skin, making it harder for heat to escape the body at all. And a wider group of drugs, for Parkinson’s, overactive bladder, allergies, and breathing conditions, share the same sweat-blocking effect as older antidepressants.
Why older adults face the highest risk
A study in US revealed, people over 65 are usually more vulnerable to heat to begin with, and they’re also more likely to be juggling multiple prescriptions at once, which multiplies the danger. Research on older patients taking diuretics, antipsychotics, beta blockers, and blood pressure drugs found they were at greater risk of heat-related hospital visits during summer, even without a heatwave happening.Doctors admit science hasn’t fully mapped out which drug combinations are riskiest, but the pattern is clear: more medications generally means less built-in protection from heat.
What this means for you
None of this means people should stop taking prescribed medication, that carries its own risks. But experts say it’s worth knowing if your medicine falls into one of these categories, especially if you work outdoors, live without air conditioning, or reside in a concrete-heavy city with little shade.Simple habits drinking water consistently, resting during peak heat, and recognising early symptoms like dizziness or unusual fatigue can go a long way. And if something feels off during a heatwave, it’s worth checking with a doctor rather than assuming it’s just the weather.