It might look like just another wellness fad, but cold-water immersion — whether through open-water swims or quick ice baths — has a long and intriguing history. Once favoured by philosophers and statesmen, it’s now being rediscovered as a potential mental health tool. But before you dive in, experts say it’s worth understanding both the benefits and the risks.
Dr Mark Harper, an anaesthesiologist and researcher, still remembers his first chilly swim in the south of England two decades ago. “It was August, but the jolt was immediate — it took my breath away,” he recalls. The shock lasted for a minute or two before his body adjusted. What followed, though, was unexpected: a surge of well-being. “I remember getting out of the water and feeling so good,” he says. “I wasn’t expecting that.”
That post-swim euphoria piqued Harper’s curiosity as a physician. Could this brief, controlled stress response have therapeutic effects? “For now, we have a very strong base, but not hard evidence, that cold-water immersion is effective for mental health,” he explains. Studies suggest possible benefits for mood, depression, and general well-being, though more data is needed to draw firm conclusions.
Harper points to the principle of hormesis — the idea that small doses of stress, whether through exercise or environmental exposure, can trigger positive adaptations. “The cold has a very strong effect on the body,” he notes, adding that the mental health benefits could stem from a combination of factors: the social nature of group swims, the exercise itself, and the confidence that comes from taking on a challenge. “People often say, ‘If I can do this, I can do anything.’ It’s a real confidence builder.”
Still, not all experiences are positive. Dr Mike Tipton, a physiologist at the University of Portsmouth who has studied human responses to extreme environments, warns that cold-water immersion isn’t without danger. In a paper co-authored with Harper, aptly titled Cold Water Immersion: Kill or Cure, the researchers stressed that cold exposure can be both “threat or treatment depending on circumstance.”
Sudden immersion in frigid water can trigger an involuntary gasp and rapid breathing — a combination that can quickly lead to drowning. “Deaths from cold-water immersion are not uncommon,” Tipton says, urging caution and common sense.
So how cold is cold enough? You don’t need to plunge into icy waters to feel the effects. “Entering water between 20°C and 15°C for just a few minutes is sufficient,” Tipton advises. Colder temperatures may enhance the response, but exposure time should be limited. “I wouldn’t go below 12°C or stay in longer than two minutes,” he says.
The body’s cold-shock response — including endorphin release, stress hormone spikes, and anti-inflammatory effects — appears to underpin the reported benefits. But longer isn’t better. “Sitting in cold water for as long as possible fills me with horror,” Tipton admits. Prolonged exposure could damage nerves or blood vessels, and in severe cases, lead to frostbite-like injuries.
So if you’re tempted to test the waters, start slow, stay safe, and treat the experience as a mindful challenge — not a race against the clock. The key, as with most things wellness, lies in balance.
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