A GP has issued a warning to millions of Brits who take antidepressants about the drugs’ little-known effects on the body’s ability to regulate temperature in hot weather. Some types can make people more sensitive to heat, potentially increasing the risk of heat exhaustion and stroke. Dr Sameer Sanghvi, a practising GP and Clinical Technology Lead at LloydsPharmacy Online Doctor, explained: “Temperature dysregulation can be a risk when taking certain types of antidepressants and antipsychotics.

"Common antidepressants can all stop the temperature regulating area of the brain functioning as it should. Serotonin-noradrenaline reuptake inhibitors (SNRIs) and selective serotonin reuptake inhibitors (SSRIs) are some of the most commonly prescribed antidepressants. 

“However, SNRIs are known to cause excessive sweating and thus dehydration, while SSRIs have been linked to heat intolerance and heat stroke.”

Antidepressants can disrupt the hypothalamus, a part of the brain that controls body temperature regulation. 

They may also interfere with sweating, hindering the body’s ability to cool down, or cause excessive sweating, which can lead to dehydration.

As summer approaches, Dr Sanghvi warned these side effects could be particularly dangerous because “many fundamental life processes depend on the body’s core temperature remaining within a narrow range”.

However, he said people should not stop taking them and “always consult your doctor before making changes to your mental health medication”.

The GP added: “The best thing you can do is take precautions to stay cool: stick to the shade; drink plenty of fluids and avoid alcohol; keep out of the sun between 11am and 3pm; avoid exercising in the hottest parts of the day; and wear loose, breathable clothing.”

Symptoms of heat exhaustion include tiredness, dizziness, headache, feeling sick, clammy skin and fast breathing or heartbeat.

The NHS advises that it does not usually need emergency medical help if the sufferer is able to cool down within 30 minutes.