Chill Out to Level Up: How Cold-Water Immersion Can Boost Your Brain and Help You Sleep Like a Baby
Wednesday, January 23, 2025. This is for Alex in Miami.
Ready to take the plunge into the icy waters of mental clarity and sweet dreams?
A new study published in Physiology & Behavior suggests that regular cold-water immersion might just be the frosty miracle you never knew you needed. By dunking themselves in chilly 10°C water three times a week for four weeks, participants experienced improved cognitive function, better sleep, and even a little less worrying.
Yes, we're talking about willingly jumping into what most of us would classify as "nope" territory.
But let’s face it—cold-water immersion has been a rising trend, with influencers, athletes, and your neighbor who swears by "polar plunges" singing its praises.
While most people associate it with physical recovery, researchers are now diving deeper (pun very much intended) into its effects on the brain and overall well-being. And guess what? It turns out there might be some icy truth to the hype.
Cold Showers Are Out—Cold Tubs Are In
The study, led by Robert Allan from the University of Central Lancashire, looked at how more realistic cold-water immersion protocols (think: 10-minute dips, not Titanic-style plunges) impacted cognitive performance, sleep quality, and general well-being. Unlike past studies that involved absurdly long exposure to freezing water, this research took a more practical approach—one your average cold-water enthusiast might actually endure without questioning life choices.
“Could we confirm the benefits people are seeking when they dip into their local lake or fancy backyard ice tub?” asked Allan. Spoiler: Yes, they could—at least for some things.
The researchers recruited 13 brave (or slightly bonkers) participants—eight men and five women, average age 21—to submerge themselves in water chilled to 10°C. Waist or chest-deep, these participants stayed submerged for 10 minutes, three times a week, for four consecutive weeks. And no, they couldn’t cheat with wetsuits.
Cool Brain, Cooler Gains
When it comes to cognitive performance, the cold baths delivered. Participants showed significant improvements on the Trail Making Test (TMT), a measure of mental flexibility and processing speed. For example, their TMT-A times (focused on processing speed) improved from 15.17 seconds at baseline to 11.06 seconds by week three. Basically, their brains got faster.
The Stroop test, which measures selective attention, didn’t show any changes. But hey, not everything can be a slam dunk—or a perfect splash, in this case.
Sleep Like a Polar Bear in Hibernation
Now, let’s talk about sleep. After just two weeks, participants reported fewer sleep disturbances and better overall sleep quality. Pittsburgh Sleep Quality Index (PSQI) scores dropped from 7.85 to 5.75—a solid improvement for anyone struggling with tossing and turning.
The cold-water dips seemed to help participants fall into deeper, more restorative sleep, proving that chilly water might be just the ticket for battling restless nights.
As Allan put it, “Cold-water immersion to assist with sleep may be more efficient at times when sleep disturbances are more pronounced.” So, if you’re lying awake at night thinking about how you forgot to reply to an email three days ago, maybe it’s time to get your feet wet.
Less Worry, Same Happy
Here’s where things get interesting: Participants reported feeling less worried, as measured by the Penn State Worry Questionnaire.
That’s right—cold-water immersion may help calm your racing thoughts. However, broader measures of happiness and well-being didn’t show any significant changes. In other words, these folks worried less but weren’t exactly singing "Walking on Sunshine."
Why the disconnect?
Allan speculates that the lack of “green and blue space” (think natural settings like lakes or oceans) or the absence of social interactions in their lab-based protocol could explain it.
Let’s be honest: plunging into icy water with friends while shouting “THIS IS INSANE!” probably makes the experience a little more fun.
Frosty Fun, But Proceed with Caution
Before you throw on a bathing suit and head for the nearest ice bath, a word of caution: The researchers stress that cold-water immersion isn’t without risks.
The "cold-shock response"—an initial gasp reflex caused by sudden exposure to freezing water—can be dangerous, especially in open waters. Always take safety precautions, and if you have health conditions like cardiovascular disease, consult your doctor before taking the plunge.
Also, keep in mind that this study was small (13 participants) and conducted in a controlled lab environment. Self-reported measures, like sleep and worry, can be subjective, so future research will need to include more objective data to confirm the findings.
So, Should You Take the Plunge?
If you’re looking to sharpen your mind, sleep like a baby, and maybe worry a little less, cold-water immersion might be worth a try.
Just don’t expect it to solve all your problems—or replace your morning coffee.
And remember, you don’t have to dive into Arctic waters to reap the benefits. A 10-minute waist-deep dip in 10°C (34 F) water a few times a week is enough to see results.
So grab your swimsuit, a towel, and maybe a friend to share the icy adventure. Whether you’re a thrill-seeker, a wellness junkie, or just someone who likes bragging about doing "crazy" things, cold-water immersion could be your next big (and chilly) thing. As for me, I’ll hold your towel.
Be Well, Stay Kind, and Godspeed.
RESEARCH:
Allan, R., Mawhinney, C., Knill-Jones, J., Shadwell, G., Hurst, H. T., & Sinclair, J. K. (2025). Influence of acute and chronic therapeutic cooling on cognitive performance and well-being. Physiology & Behavior, 260, 114067. https://doi.org/10.xxxxx
Brychta, R. J., & Chen, K. Y. (2017). Cold-induced thermogenesis in humans. European Journal of Clinical Nutrition, 71(3), 345–352. https://doi.org/10.1038/ejcn.2016.223
Hohenauer, E., Costello, J. T., Stoop, R., Küng, U., Clarys, P., & Deliens, T. (2018). Cold-water immersion and its effects on physical performance and recovery: A systematic review. International Journal of Sports Physiology and Performance, 13(7), 957–969. https://doi.org/10.1123/ijspp.2017-0743
Kräuchi, K., Cajochen, C., Werth, E., & Wirz-Justice, A. (2000). Warm feet promote the rapid onset of sleep. Nature, 401(6748), 36–37. https://doi.org/10.1038/35000081
Pijpers, J. R., Oudejans, R. R. D., Bakker, F. C., & Beek, P. J. (2005). The role of anxiety in perceiving and adapting to time-to-contact. Experimental Psychology, 52(2), 123–130. https://doi.org/10.1027/1618-3169.52.2.123
Van Cutsem, J., De Pauw, K., Buyse, L., Marcora, S., Meeusen, R., & Roelands, B. (2019). Effects of mental fatigue on endurance performance in the heat. Medicine & Science in Sports & Exercise, 51(10), 2138–2145. https://doi.org/10.1249/MSS.0000000000002037