In the most comprehensive systematic review and meta-analysis of its kind, University of South Australia researchers have taken a deep dive into the effects of cold-water immersion on health and wellbeing.
Analysing data from 11 studies with 3177 participants, researchers found that cold-water immersion may lower stress, improve sleep quality, and boost quality of life.
UniSA researcher Tara Cain says the study reveals time-dependant and nuanced effects on health and wellbeing measures.
“Cold-water immersion has been extensively researched and used in sporting contexts to help athletes recover, but despite its growing popularity among health and wellbeing circles, little is known about its effects on the general population,” Cain says.
Just 12 hours #
“In this study, we noted a range of time-dependant results. Firstly, we found that cold-water immersion could reduce stress levels, but for only about 12 hours post exposure".
Just three months #
“We also noted that participants who took 20, 60, or 90 second cold showers reported slightly higher quality of life scores. But again, after three months these effects had faded.
29% #
“Benefits may be gained from cold showers as well, with one study reporting that participants who took regular cold showers experiencing a 29% reduction in sickness absence".
Just males #
“We also found some links to cold-water immersion and better sleep outcomes, but the data was restricted to males, so its broader application is limited."
Very little evidence #
“And while there have been many claims that cold-water immersion experiences can boost your immunity and mood, we found very little evidence to support these claims.”
Inflammation #
Co-researcher, UniSA’s Dr Ben Singh says the study also showed that cold-water immersion caused a temporary increase in inflammation.
“At first glance this seems contradictory, as we know that ice baths are regularly used by elite athletes to reduce inflammation and muscle soreness after exercise,” Dr Singh says.
“The immediate spike in inflammation is the body’s reaction to the cold as a stressor. It helps the body adapt and recover and is similar to how exercise causes muscle damage before making muscles stronger, which is why athletes use it despite the short-term increase."
Do you have pre-existing health conditions? #
“Knowing this, people with pre-existing health conditions should take extra care if participating in cold-water immersion experiences as the initial inflammation could have detrimental health impacts.”
50/50? #
Researchers say that while the findings highlight the potential benefits of cold-water immersion, they also underscore the highly time-dependent and contextual nature of its effects.
“Whether you are an elite athlete or everyday wellness seeker – it’s important to understand the effects of what you put your body through,” Cain says.
More studies needed #
“Right now, there isn’t enough high-quality research to say exactly who benefits most or what the ideal approach is to cold-water immersion. More long-term studies, among more diverse populations, are needed to understand its lasting effects and practical applications.”
Diving in the paper #
In the paper the researchers pointed the study’s objective was to make a “systematic review and meta-analysis aimed to evaluate the psychological, cognitive, and physiological effects of CWI -cold-water immersion- in healthy adults.
Methods: _“Electronic databases were searched for randomized trials involving healthy adults aged ≥ 18 years undergoing acute or long-term CWI exposure via cold shower, ice bath, or plunge with water temperature ≤15°C for at least 30 seconds. Outcomes of interest were sleep, stress, fatigue, energy, skin health, immunity, inflammation, mental wellbeing, depression, anxiety, mood, concentration, and alertness or focus. Meta-analyses were conducted using RevMan software (version 5.4), applying random effects models to calculate standardized mean differences (SMD) between pre- and post-CWI exposure outcomes. Risk of bias was assessed using the PEDro scale.
Results: Eleven studies were included, comprising 3177 total participants and a mean PEDro score of 6.4 (n = 7 moderate quality, n = 4 high quality). CWI interventions were performed in baths (n = 10) or showers (n = 1) at temperatures ranging from 7°C to 15°C and durations ranging from 30 seconds to 2 hours. The meta-analysis revealed significant increases in inflammation immediately (SMD: 1.03, [95% CI: 0.37, 1.68], p < 0.01) and 1 hour post CWI (SMD: 1.26, [95% CI: 0.59, 1.94], p < 0.01), indicating an acute inflammatory response. A significant reduction in stress was observed 12 hours post-CWI (SMD: –1.00, [95% CI: –1.40, –0.61], p < 0.01), however, no significant effects on stress were detected immediately (SMD: –0.09 [95% CI: –0.45, 0.63], p > 0.05), 1 hour (SMD: –0.29 [95% CI: –0.66, 0.08], p > 0.05), 24 hours (SMD: –0.06 [95% CI: –0.50, 0.38], p > 0.05), or 48 hours (SMD: 0.09 [95% CI: –0.28, 0.46], p > 0.05) post-exposure. While meta-analysis showed no significant effects on immune function immediately (SMD: –0.16 [95% CI: –0.82, 0.51], p > 0.05) or 1 hour (SMD: –0.18 [95% CI: –1.09, 0.74], p > 0.05) post-CWI, narrative synthesis suggested longer-term benefits, including a 29% reduction in sickness absence among participants who took cold showers. Improvements were also observed in sleep quality and quality of life, but not mood.
Conclusions:
This systematic review suggests that CWI delivers time-dependent effects on inflammation, stress, immunity, sleep quality, and quality of life, offering potential practical applications for health practitioners considering CWI for stress management and wellbeing support. However, the current evidence base is constrained by few RCTs, small sample sizes, and a lack of diversity in study populations. Future high-quality RCTs are needed to examine the long-term effects of CWI, its impact on diverse health outcomes, and optimal CWI protocols.
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The paper Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis was published in PLOS One. Authors: Tara Cain, Jacinta Brinsley, Hunter Bennett, Max Nelson, Carol Maher & Ben Singh. Published: January 29, 2025 https://doi.org/10.1371/journal.pone.0317615
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You can read here the original article.