Cold-Water Swimming for Your Health? These Docs Say Jump In

Andrea Goto

November 15, 2023

Adam Boggon, MBChB, was working at the Royal Free Hospital in North London during the city's second wave of COVID-19. "I was effectively living in the hospital," he recalls. "It felt like I was going 10,000 miles per hour, trying to corral hundreds of medical students and doctors."

Adam Boggon, MBChB

During a national lockdown, there were few places Boggon could escape to, but the Hampstead Heath swimming ponds mostly remained open. He swam there regularly to exercise and recharge even in winter.

"Swimming in cold water takes you out of yourself," Boggon says. "It was such a release for someone who grew up in a rural place and had access to green space, even though the water is murky." It also hovers around 50 °F (10 °C).

Jumping into cold water, well, kind of stinks. So why do it? It's not only for bragging rights. A growing number of studies suggest significant mental and physical health benefits to swimming in cold water, specifically to improve depression symptoms and even ease inflammatory conditions.

And a lot of that research is driven by medical pros who love to do it themselves.

For Boggon, swimming in frigid water is uncomfortable, but he feels that a sensation of calmness follows that makes the plunge more than worth it. Now a Fulbright Scholar at Harvard, where he studies public health and health management, Boggon is able to frequent the fabled Walden Pond just outside of Boston, Massachusetts.

As Thoreau himself said, "You can never have enough of nature."

Yes, even if it's really, really cold.

Taking a Deeper Dive

Heather Massey, PhD, a senior lecturer in Sport, Health and Exercise Science at University of Portsmouth blames her father, a dinghy sailor, for her affinity for cold-water swimming.

Heather Massey, PhD

And she's done more than most, including an epic 16-hour crossing of the English Channel. The water temperature was in the upper-50s °F, and she swam without a wetsuit. "Time just seemed to collapse," she has shared about the experience.

While working on her PhD and studying the effects of environmental physiology, in particular what happens to the body when it gets hot or cold, Massey's hobby and studies seemed to coalesce.

Massey's research initially focused on the hazards around being in cold open water. But she also noticed a growing trend of people claiming health benefits from the practice. "People started to talk about experiencing improved symptoms of depression or improved mental health from their activities in the water," she says.

She partnered with another outdoor swimming enthusiast, Hannah Denton, a counseling psychologist working for the National Health Service in the United Kingdom. Denton was publishing papers on the potential impact that outdoor swimming may have on people with depression and how it could improve mental health in general. She also regularly engages in cold-water swims to boost feelings of mindfulness and peace.

"Having the experience of being so close to nature, as well as the strong sensory experience of being in cold water, does really encourage you to be in the moment," Denton wrote in an article for the Sussex Mindfulness Centre. "My experiences of sea swimming and mindfulness support each other. Both have made me feel more comfortable with my body, to have more of a present moment focus, to pay attention to my breathing and to gain distance from difficult thoughts."

Over the past few years, Massey and Denton have moved from fairly small-scale studies with no real controls to today, completing a randomized controlled trial and looking at the impact that outdoor swimming may have on people living with mild to moderate depression.

"At first, people sort of thought our idea was a bit wacky," says Massey. "Now, the popularity of open-water swimming has really blossomed, and so has this area of research. We're starting to build more rigor into the work."

Like all the researchers and physicians interviewed for this article, Massey hesitates to claim that cold-water swimming is a "cure" that should be medicalized.

"It's not about prescribing it or forcing people to do it," says Massey. "This is not something that a doctor should write on a prescription and say you should go and have eight 1-hour sessions of swimming."

(Not Yet) a Common Cure

Enter into the conversation Mark Harper, MD, PhD, consultant anesthetist at Sussex University Hospitals in the United Kingdom and Kristiansand, Norway. Harper is the author of the 2022 book, Chill: The Cold Water Swim Cure - A Transformative Guide to Renew Your Body and Mind.

Mark Harper, MD, PhD

Harper grew up swimming in pools, and it wasn't until his pool closed for 2 weeks that he ventured into the sea. He recalls walking up the beach afterward, thinking, God, this feels good, and from that moment on, he became hooked on outdoor swimming and curious about its therapeutic potential.

The "cure" in the book's title, Harper explains, is being used in the historical sense of "treatment," as in the first medical book about sea-bathing written over 250 years ago. Harper acknowledges that the connection to health is still speculative. "However, the circumstantial evidence, the feedback from participants and early study data for its benefits are now very strong," he says.

In a small study published in 2022, Harper and colleagues took 59 people with anxiety and depression and put them through a sea-swimming course. Afterward, 80% showed a clinically significant improvement in their mental health.

More recently, Harper and his team of researchers released a survey to determine how many people were using cold-water swimming as a treatment for a mental or physical ailment. "We thought 30 or 40 people would respond, but we ended up with over 700," says Harper. "The majority were using it for mental health but also included inflammation-related conditions."

Over two decades, Harper has seen dramatic success stories. In his book, he recalls a good friend who, in his early 20s, suffered from Crohn's disease so badly he couldn't walk up the steps to his parents' house. The friend turned to outdoor cold swimming as a low-impact workout and began noticing the symptoms of his disease were improving. Within months, he was able to go off his medications. In 2022, he completed 52 triathlons: one per week for the entire year.

How Cold Exposure May Play With Your Brain

Vaibhav Diwadkar, PhD, professor of psychiatry and behavioral neurosciences at Wayne State University School of Medicine, in Michigan, is studying how human brain networks respond to cold exposure. Diwadkar and his colleague, Professor Otto Muzik, PhD, began by putting volunteers in a rubber suit with thin tubing and infusing the tubing with temperature-controlled water. Meanwhile, they collected functional brain imaging data to analyze which parts of the brain were responding as body temperature changed.

Vaibhav Diwadkar, PhD

The data showed that the cold exposure made certain areas of the brain very active, including some that have been associated with the regulation of mood.

Diwadkar posits that controlled exposure to cold serves as a low-level stressor that knocks different systems within the brain and body out of homeostasis. Once the stress is removed, the brain responds by releasing neurotransmitters that enhance mood, frequently leading to feelings of euphoria in participants.

"We don't have direct evidence of such a mechanism, but it's a reasonable speculation," says Diwadkar.

However, Diwadkar points out that science writers in the media often portray topics such as this one in black and white, which is, "oversimplifying the scientific complexity of biology."

Clearly, more research needs to be done on the potential therapeutic benefits of cold-water swimming. But for those suffering from anxiety, depression or chronic illness, if taking a cold dip makes you feel better, the why and how might be beside the point.

Plus, as Harper points out, it's an easy and accessible therapy.

"All you need is some water — enough to submerge your entire body in — that's less than 68 °F (20 °C)," explains Harper. "If you stay long enough to get over that initial shock, which is just two or three minutes, then you've got the effect. If you get out and want to go back in again, then you've done it right."


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