Take the plunge
Wild swimming and cold water immersion have surged in popularity since the hobby first went viral on TikTok during lockdown in 2020. Us enthusiasts swear by our transformative effects on both mental and physical health. But what does science say? Is there real neurological and physiological evidence behind these benefits? You should know by now that I’m a woman of evidence backed science, so of course I took the time to dissect it for you. This deep dive explores the neurochemistry, physiological adaptations, and long-term health benefits of cold water therapy.
How Your Body Reacts to Cold Water
The first thing you’ll notice when plunging into cold water is the cold shock response to a rapid, involuntary reaction controlled by the autonomic nervous system. This response is your body’s way of saying, “what the fuck is happening?”. When you enter water below 15°C (59°F), your body activates the sympathetic nervous system (SNS), triggering:
A sharp intake of breath (involuntary gasp reflex)
Rapid heart rate increase (tachycardia)
Peripheral vasoconstriction (blood vessels constrict to preserve core heat)
Increased adrenaline and noradrenaline (stress hormones flood the system)
This reaction peaks within 30 seconds of immersion and subsides after around 2-3 minutes as the body adapts (Tipton et al., 2017). If you can regulate your breathing through this phase, you’re already essentially hacking your nervous system and overriding the panic response. Once you’ve survived the initial shock, your brain chemistry undergoes significant changes. Cold water exposure influences key neurotransmitters that impact mood, pain perception, and mental clarity. You know how I’m always harping on about wild swimming coming in clutch when I’m deep in the depressive pit? Yeah, it’s science. The changes in brain chemistry while wild swimming are equal to the brain chemistry of a cocaine high. It takes almost a week for the dopamine build up to fade from cold water therapy, on the other hand, the fade for cocaine is around 15-30 minutes. If you’re a depressed individual, you should most definitely give a cold plunge or a wild swim a go. And if you’re trying to go clean of an addiction that relies on a dopamine flood (cocaine, vaping, opioids, gambling, phone addiction), then you could consider swapping a sesh for a swim.
Cold water immersion has been shown to increase dopamine levels by up to 250% (Jansky et al., 2006). Dopamine is the brain’s “reward” chemical associated with pleasure, motivation, and focus. This explains the post-swim euphoria, often described as a natural high.
This exposure significantly elevates noradrenaline (norepinephrine for my American friends), a neurotransmitter that plays a crucial role in focus, attention, and reducing inflammation (van den Burg et al., 2007). This is one of the many reasons cold water swimming is being explored as a treatment for depression and anxiety; higher noradrenaline levels correlate with improved mood and resilience (can vouch).
The pain of cold water triggers the release of beta-endorphins, which are endogenous opioids that reduce pain and promote a sense of well-being (Shevchuk, 2008). This is part of why wild swimming is linked to lower chronic pain levels as it triggers our “natural painkiller” response.
Mental health benefits
For me, wild swimming started as just a pastime, and I fell into the mental health benefits the more I indulged the hobby. Like I previously mentioned, it’s being investigated as a legitimate therapy for mental health conditions. A 2018 case study published in BMJ Case Reports documented a woman with severe depression who began regular cold water swimming. Within a few months, she was able to reduce and eventually stop her antidepressant medication (Harper et al., 2018). The proposed mechanism? A combination of:
Increased dopamine and serotonin
Activation of the parasympathetic nervous system, which calms the body
Psychological resilience training, overcoming the initial discomfort of cold exposure may rewire the brain to handle stress better
It’s worth noting that I know a case study yielding a favourable result when researching mental health isn’t enough to draw a conclusion. I’m also fully aware of how complex and nuanced dealing with poor mental health is. I personally still take medication for my mental health, and have done on and off since my teenage years. For me, the medication isn’t always quite enough, and I don’t want to up my dosage because that comes with side effects that I can’t really handle. So I flitter somewhere in the middle; my meds get me halfway and I try my best to cross the finish line every day. Wild swimming is one of the things that spurs me on when I need to dig deep. Most importantly, it’s quick and accessible for me, and costs close to nothing. When I’m really in pits and I can’t even bring myself to do anything, I’ll force myself to have a long cold shower. It’s where I suggest everyone starts, and it’s something that I always go back to even as an experienced swimmer.
Emotional regulation
Cold water immersion stimulates the vagus nerve, which is crucial for activating the parasympathetic nervous system (PNS) (Bretherton et al., 2019). The PNS is responsible for the “rest and digest”functions, counteracting stress and promoting a sense of calmness within us. Regular vagus nerve stimulation has been linked to lowering our heart rates, reducing our anxiety, and improving our emotional resilience. Repeated wild swimming trains the vagus nerve to activate more efficiently, leading to long-term reductions in stress responses. This is why many cold water swimmers report feeling calm, clear-headed, and emotionally balanced after a swim, even on more challenging days. Personally, I feel less depressed and anxious for days after a cold dip.
What about physical health benefits?
Beyond its impact on the brain, cold water swimming triggers significant physiological adaptations that improve long term health. Cold exposure increases the production of white blood cells and anti-inflammatory cytokines (these are small proteins involved with growing immune system cells) (Kox et al., 2014). A study on winter wild swimmers found that regular cold water immersion significantly enhanced immune function and reduced frequency of infections (Dugue & Leppanen, 2000). Chronic inflammation is linked to diseases like diabetes, cardiovascular disease, and neurodegenerative conditions such as Alzeimer’s, Huntington’s, and Parkinson’s disease. Cold water immersion reduces systemic inflammation by lowering levels of pro-inflammatory cytokines (Peake et al., 2017). This is why athletes use ice baths to recover from intense exercise; it speeds up muscle repair and reduces soreness by way of minimising and/or inhibiting that inflammatory process.
Continued research also demonstrates that cold plunges activate brown adipose tissue (BAT), a type of fat that burns calories to generate heat. Studies show that regular cold exposure increases BAT activity and improves insulin sensitivity, making it a potentially useful tool for people to help manage the health risks of obesity and type 2 diabetes, if they so wish (Cannon & Nedergaard, 2011).
And lastly, probably the most important physical health benefit in my opinion: wild swimming forces your cardiovascular system to become more efficient. Over time, repeated exposure:
Improves circulation by training blood vessels to constrict and dilate more effectively
Lowers blood pressure and resting heart rate (Siems et al., 1999)
Reduces the risk of stroke and heart disease due to improved vascular health
It’s not just about cold water
While the physiological benefits of cold exposure are impressive, wild swimming actually offers up even more psychological benefits due to its connection with nature. Have you ever heard of Blue Mind Theory? Well, research indicates that being near, in, or on water has a profound calming effect on the brain (Nichols, 2014). The rhythmic motion of swimming also mimics bilateral stimulation, which is used in therapies like EMDR for various types of PTSD. Before being diagnosed with Dissociative Amnesia, I was focusing my therapy on EMDR, which was, for the most part, beneficial enough for me to see how it would work well in other cases. Swimming in natural water forces presence. Each stroke demands attention to breath, body position, and movement. This focus on the moment induces a flow state, a neurological condition associated with heightened creativity, reduced anxiety, and peak performance (Csikszentmihalyi, 1990). For me, swimming in general, not just wild swimming, is the quickest and easiest way for me to feel grounded.
So, will you take the plunge? If you’re local to Sheffield/Peak District, I run a bimonthly wild swimmers meet up that is beginner-friendly. You can find more details over on @swim_wildly on Instagram or subscribe to our newsletter for instant alerts. It’s all completely free!
