Commuters travelling on the London Underground this Bank Holiday weekend face more than just crowded carriages – those taking antidepressants could be at heightened risk of heat intolerance as temperatures soar. With amber heat health alerts in place across several regions including London, and the mercury forecast to reach 33°C – potentially breaking spring records – the Victoria Line, already the hottest on the network, is expected to be particularly punishing. Transport for London recorded 32°C on the line in August 2024, and data shows average platform temperatures have risen by around 30% over the past decade, with winter readings never dropping below 25°C in recent years.
Millions of people in England are affected. In the 2024/25 financial year, 92.6 million antidepressant items were prescribed to an estimated 8.89 million identified patients – a 3.94% increase in prescriptions and a 1.61% rise in patient numbers compared with the previous year. Over the five years to March 2025, the NHS spent £1.23 billion on these medications. Yet many of those taking them may be unaware that common drugs – including Selective Serotonin Reuptake Inhibitors (SSRIs), Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) and tricyclic antidepressants – can interfere with the body’s ability to regulate temperature, making overheating more likely in sweltering environments such as the Tube.
Dr Asim Cheema, an internal medicine and cardiology specialist at Your Doctors Online, explains that certain antidepressants impair thermoregulation through two main mechanisms. “Some affect the hypothalamus, which controls temperature regulation, while others reduce sweating, making it harder for the body to cool down naturally,” he says. This can increase the risk of heat exhaustion, dehydration and even heatstroke during periods of high temperature. Dr Cheema notes that commonly prescribed SSRIs such as sertraline and fluoxetine, SNRIs including venlafaxine and duloxetine, and tricyclic antidepressants like amitriptyline are all implicated. He adds that other medications – antipsychotics, beta-blockers, diuretics and some antihistamines – can also affect heat tolerance.
The consequences can escalate quickly. Heat exhaustion typically presents with tiredness, dizziness, headache, nausea, excessive sweating or pale clammy skin, muscle cramps, fast breathing or heartbeat, a high temperature of 38°C or above, and extreme thirst. If left untreated, it can progress to heatstroke – a life-threatening condition characterised by confusion, lack of coordination, hot flushed dry skin, a body temperature exceeding 40°C, rapid pulse, fast breathing, seizures and loss of consciousness. Anyone experiencing heat exhaustion symptoms that do not improve within 30 minutes of cooling down, or who suspects heatstroke, should call 999 immediately. For less severe concerns, NHS 111 can provide advice.
Despite TfL’s efforts to cool the network – including increasing ventilation shaft capacity, installing air cooling units and chillers at busy stations, and using groundwater for cooling – the Victoria Line has remained largely unaffected by these measures. The line’s average platform temperature in August 2024 was around 28°C, nearly 44% higher than the external temperature. This makes it a particular hazard for those on medications that compromise the body’s natural cooling systems.
Dr Cheema advises that taking antidepressants does not mean people cannot enjoy summer, but it does require extra caution during extreme heat. He recommends recognising warning signs such as headache, nausea, confusion or feeling faint; staying well-hydrated because dehydration can worsen side effects like dizziness or lightheadedness; dressing in breathable, loose-fitting clothes; and planning ahead by carrying water, using cooling towels, and avoiding peak travel times if possible.
Dr Nikki Kanani, Chief Strategy and Innovation Officer at Aneira Health, stresses the importance of acting quickly if symptoms appear. She advises moving to a cooler place, sipping water slowly, and using a fan or damp cloth to cool down. “Avoid pushing through your symptoms, listen to your body and importantly, talk to your doctor if symptoms persist – you may need to adjust when you take your medication or review alternatives,” she says. To protect against heat, she suggests avoiding direct sun exposure between 11am and 3pm, wearing a hat and SPF, taking breaks in the shade, and planning outdoor activity for early morning or evening. For those braving public transport, she recommends travelling outside peak times, carrying water, wearing breathable clothing, and using a hand fan. “If you feel faint or unwell, get off at the next stop, find somewhere cool, and rest. Never ignore symptoms – overheating can happen quickly.”
Dr Kanani highlights that this side effect, while common, is often overlooked and not routinely discussed – particularly when medications are first prescribed in cooler months or when clinical consultations focus on mental health support. “As heatwaves become more common, we need to talk more openly about how medication affects our health in real-world conditions – especially for women and people with long-term conditions,” she adds. The Aneira Health platform itself is developing precision medicine for women’s health, aiming to address systemic gaps in care.
Social media is already filling with complaints from those on antidepressants who describe feeling as though they are “melting” or being “burnt alive” as temperatures hit 30°C. With the current heatwave driven by an African plume and a shift in jet-stream winds – and climate change making such extremes roughly three times more likely – the combination of soaring temperatures, London’s hottest Tube line, and millions of prescriptions for drugs that impair the body’s ability to cool down presents a growing public health concern that, as Dr Kanani puts it, demands far more open discussion.