Dip into the sea in winter, and adrenalin and endorphins flood your bloodstream – making you feel panicked, and then fantastic. Do it every day and you could improve your ability to cope with stress, reduce inflammation and even alleviate the symptoms of depression. Helen Glenny reports.
Rüder, 56, is at ease in this group. They’re mostly women, mostly working age, united by enthusiasm and a good-humoured reluctance around their Friday ritual. A few of them swim lengthways along the beach while the rest paddle around, catching up on the minutiae of each other’s lives. (Friday evening happy hour is also on the Dippers’ schedule, so they know each other well.) Passers-by could be fooled into thinking Rüder has done this all her life, but here’s what’s not obvious: Rüder’s always hated swimming. The ocean gives her the creeps, and two years ago, she felt completely alone, unable to summon the will to get out of bed.
In 2017, a sudden and destabilising change in circumstances saw Rüder descend into depression. Her experience was devastating, but not unusual: depression afflicts one in six New Zealand adults at some point in their lives. It affects more women than men, and is most common between the ages of 45 and 54.
After months of struggling in isolation, Rüder, desperate for a reason to get out of bed, agreed to join friends for “Wet July”: a dip in the sea every day that month, no exceptions. Unknown to Rüder at the time, scientists are investigating the idea that frequent cold-water swimming can help ameliorate the symptoms of depression, through improving your ability to cope with stress and fighting chronic inflammation. She was starting a hobby that would become a habit; one that might eventually wrest her out of the depths.
Tipton spent years working with cold-water swimmers, and grew curious about the benefits of a chilly plunge. “You start hearing these claims: ‘I never have a cold,’ or ‘I feel really elated when I come out of the water.’ That entices you to have a look at what’s going on.”
In 2017, he and his colleagues published a paper titled Cold Water Immersion: Kill or Cure? It outlined the dangers: cold-water immersion is a hazard, a precursor to drowning, cardiac arrest and hypothermia. But it also acknowledged another idea – that, when done safely, it can have health benefits. He and his co-authors discussed two physiological changes that happen after habitual cold-water immersion: over time, you adapt to the stress of cold water, which dampens your response to other stressors (deadlines, divorce and the like); and that adaptation goes on to reduce the levels of inflammation in your body.
Tipton and his colleagues now immerse volunteers in cold water in their lab to study how they adapt over repeated dunks. In 2016, they did just that for a segment on cold-water swimming in the BBC TV series The Doctor Who Gave Up Drugs, which featured a 24-year-old, Sarah, who’d suffered from major depression and anxiety for most of her life and aspired to be medication-free.
In his Portsmouth lab, Tipton sat Sarah in a hanging seat and lowered her up to the neck into 12°C water, where she stayed for five minutes, enduring the rigours of a cold plunge. Over the course of one day, she did six immersions.
After Sarah’s second dip, Tipton says she was miserable. “We gave her the option to call it a day, but she insisted on pushing on.” By the end of the sixth immersion, something had changed, and she told Tipton she was the happiest she’d felt in years.
Rüder and her husband Rob spent a year travelling around Europe, and when they returned, both of their adult children moved out of home. One moved into a flat, and a few days later, the other went to university.
“I’ll never forget that day,” she says. “We dropped Charlie at his hall, then we had a cup of tea, like we always do. That’s when Rob told me he was leaving me.” After 25 years of marriage, her husband’s request for separation came without warning. “There were so many parts to it: I didn’t know when he’d planned it, I didn’t see it coming. He was my soulmate.” Within a month, Rob had left New Zealand.
Rüder was living alone for the first time in decades, and rapidly withdrew from her social circle. “I went down this deep, deep hole,” she says. “I couldn’t see any reason to live, except to see the kids. I was alone, and I had no idea what to do with myself. Nothing made sense anymore.”
For five months, Rüder endured her depression with help from her GP and a grief counsellor. Then, in an uncharacteristic spurt of motivation, she agreed to join her friends for Wet July. “It was a big turning point for me. It gave me a reason to get out of bed.”
Rüder’s first week of Wet July acted like a field version of Tipton’s lab-based habituation process. “I was definitely nervous,” she admits. In July, the average water temperature at Sumner is 9-10°C. The group had agreed to do a quick in-out, but ended up staying in the water for five or six minutes. “We felt like we were doing something mad. We came out with smiles on our faces, we were buzzing.”
Those effects wore off quickly, but they gave Rüder relief from her depression for a short time each morning. “I was coming out a little bit lighter. I can’t even say happier – I didn’t come out happy – but that stuff just wasn’t there. For five minutes in the morning, it was just okay.”
That initial buzz felt by Rüder is a result of what Tipton has termed “cold shock”. Cold water is a stressor – a big one, he says, because as tropical animals, we’re most comfortable at around 21°C, when clothed and not moving. “So being plunged into cold water is about as stressful as it can get.”
Anyone who’s taken a wintery dip will recognise the feeling: the receptors just under your skin respond to a sudden drop in temperature, you gasp involuntarily, then continue to hyperventilate. The shock activates your sympathetic nervous system, responsible for the fight, flight or freeze response.
Adrenalin is released into the bloodstream, where it prompts a number of physiological reactions: your heart rate increases and your blood pressure goes up. It also triggers the release of glucose and fats into the bloodstream, providing an energy source for a quick escape.
As that initial surge of adrenalin subsides, the hypothalamic-pituitary axis takes over. It produces a cascade of hormones that culminates in the release of cortisol, which maintains this state of alertness for minutes to hours. With that comes a surge of beta-endorphins, naturally occurring substances that bind opioid receptors, producing euphoria and pain relief.
For Rüder, all this culminated in helping her feel better for brief periods after her morning dips. And while the effect is temporary, there are longer-term mechanisms at play.
In his lab, Tipton measures how people like Rüder adapt to cold shock, by tracking their breathing and heart rates while they’re in the water. He says adaptation happens quickly. “After about six immersions we’ve halved the cold shock response, and that reduction can last up to 14 months.”
That means half the heart rate increase, half the hyperventilation, half the panic. He’s yet to measure how often you need to dip to maintain the effects, but thinks once every five or six days should do it. This adaptation makes you less reactive to the shock of cold water, but here’s where the larger benefit lies: you can also become less reactive to everyday stress.
This is called “cross-adaptation”: adapt to one stressor and you’ll partially adapt to others. Tipton and his colleagues have shown you can habituate people to cold-water immersion; then when you take those swimmers to altitude, they have a much smaller stress response to the lack of oxygen. While there are some differences in the way the body reacts to different types of stress – physical stress and psychological stress, for example – a large element is common across them all.
“These stressors are always stimulating the sympathetic nervous system, as well as other systems responsible for cellular tolerance to stress,” he says. “We think cold-water habituation resets those systems to deal with stress better, so there’s less of a response to any stressor.”
Their early findings support the idea that cross-adaptation extends to psychological stress. “If I sit you down and give you a demanding mathematical challenge, your stress response wouldn’t be that different to if I immersed you in cold water, which means there’s a chance for cross-adaptation.”
In isolated bouts, stress is a healthy response to a perceived threat. Dr Nick Hoeh, a consultant psychiatrist and professional teaching fellow at the University of Auckland, explains how healthy stress becomes problematic when it’s prolonged. “Stress is an evolutionary requirement. I feel bad, I may even be injured, but here comes a lion. So I’m going to have this surge of cortisol and stress hormones, it’s going to energise me and get my blood flowing where it needs to be and boom, I’m escaping.”
But, he explains, minor modern stressors can also activate this response, and they tend to persist for longer, leading to chronic stress. “Say you think your boss is going to fire you. Losing your job is a big deal, so you get stressed. But this fear might occur over and over again, so you’ll develop chronic stress, which might lead to clinical depression.”
Dr Mark Harper, who collaborates with Tipton on cold water-immersion research, notes that “if you run a high level of baseline stress, you’re more likely to tip into bad stress – pathological stress”. He reasons that cold-water swimming could prevent people from slipping into chronic stress and, potentially, depression. But it could also help someone who’s already there, like Rüder. If the magnitude of her stress response is reduced, her depression may have room to recede.
Harper explains that inflammation is an important but sometimes harmful part of the stress response. Just as stress causes an adrenalin surge, preparing animals to attack or to run, it also kick-starts the immune system in preparation for possible wounding or infection. And just like stress, it’s healthy when these immune flare-ups are controlled and isolated, but becomes problematic for people who are chronically stressed. Chronic inflammation has been implicated in a wide range of conditions: atherosclerosis, type 2 diabetes, Alzheimer’s and cancer, to name a few. There’s also increasingly convincing evidence implicating it as a cause of depression.
The number of studies linking inflammation and depression is growing. Among them, one showed that rats injected with infectious bacteria exhibit “sickness behaviour”, which echoes the human experience of depression: they withdraw socially, they’re less active, and they don’t sleep well or eat normally. What’s more, when the rats were injected with inflammatory molecules, rather than bacteria, the result was the same, suggesting sickness behaviour is a response to inflammation, rather than to the bacteria itself.
Another study involving identical twins found the twin with higher levels of inflammation was more likely to have developed depression when revisited five years later. And a recent meta-analysis, pooling 26 studies that cover more than 1500 patients, showed that prescribing anti-inflammatories alongside anti-depressants enhanced the effects of the standard antidepressant treatment.
Harper believes habitual cold-water swimming can dampen the stress response, reducing inflammation. That could help prevent depression, or help those already suffering from depression to recover. Experts, however, are quick to note depression is a complex condition still not fully understood, and inflammation is likely to be just one of a number of underlying causes.
“The big problem is isolating the active ingredient,” says Tipton. “You might go down to a lake or the sea for a swim and you’ll absolutely have cold water, but you’ll also be in a nice environment, you’ll be doing some exercise, you’ll probably be doing it with friends, so to say that’s improving your mental and physical health is perfectly reasonable.”
And there may be something else coming into play, too. Recently, researchers have identified the benefits of “blue therapy” – spending time near bodies of water. A 2013 UK study on happiness in natural environments, in which 20,000 people recorded their sense of wellbeing and their current environment at random intervals, found marine and coastal environments were associated with the highest sense of wellbeing. In 2016, University of Canterbury researchers showed being able to see “blue space” – lakes, rivers or the ocean – was associated with lower psychological distress, even when factors such as income, housing quality and deprivation were controlled for.
From many angles, cold-water immersion continues to be an exciting and active area of investigation. Harper, collaborating with researchers in Tipton’s lab, has gathered preliminary data about wellbeing through questionnaires from 600 outdoor swimmers. They’re now planning collaborative studies that directly measure adaptation, inflammation and symptoms of depression in volunteers during courses of cold-water swimming at sites around England.
“One morning, I was out here in the dark, in up to my shoulders, and a fish [leapt out of the water and] hit me in the side of the head, just like that!” one says.
“Oh, we get big crabs, that’s for sure,” says another. “They can really grab hold of your toes.”
Jogging up the beach to join the group, one last dipper bounces with excitement. “I stayed in the longest... I never stay in the longest!” Later, she exhales and rolls her shoulders back, looking relaxed. “I really needed that.”
Since joining the Scarborough Dippers, Rüder has found the dipping community to be inclusive and expansive. “We dip at Sumner by the clock tower, but since then we’ve found other dipping groups. There’s one at Waikuku Beach [north of Christchurch], and there’s a dress-up beach, and a skinny dip at Taylor’s Mistake – it’s hilarious!”
Often people say they were too nervous to join, and come along months after first seeing the group at the beach or finding their Facebook page. “But they come, and now they’re weekly dippers.”
Rather than fixating on the physiological benefits of her cold-water immersion, Rüder takes a holistic view.
“I feel like dipping has been a big puzzle piece in my healing; friends and time, they’re big pieces, and there are all these other little pieces around that.
“I’m certainly not saying it’s easy. There are often a lot of mind battles going on. But you get up in the morning, and you know there are friends waiting, so you go.”
- If you have a history of heart disease, talk to your GP before you start cold-water swimming.
- Always dip with other people and, if possible, with people who are familiar with the sites.
- Choose safe places to swim.
- Make sure you can enter and exit the water quickly and easily.
- After 15-20 minutes in the water, you may begin to stiffen up. If you start to feel as if you can’t maintain a swimming stroke, get out of the water.
- Once you’re out, your core will continue to cool down for about half an hour. Warm up with warm clothes and a hot drink rather than a hot shower, and avoid driving home straight away.