BACKGROUND
Cold-water immersion (CWI) has gained popularity as a health and wellbeing intervention among the general population.
Article breakdown
Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis.
PloS one • 2025 • Vol 20, e0317615. PMID 39879231.
This paper combined results from 11 randomized trials on cold-water immersion in healthy adults. It found that cold-water immersion briefly increased inflammation right after exposure, but this effect was not clearly present later, and it did not show clear short-term improvements in stress, immunity, or mood. Some studies suggested possible longer-term benefits such as fewer sickness absences, better sleep, and better quality of life, but the evidence was limited and more high-quality trials are needed.
In short
What this paper found
This paper combined results from 11 randomized trials on cold-water immersion in healthy adults.
It found that cold-water immersion briefly increased inflammation right after exposure, but this effect was not clearly present later, and it did not show clear short-term improvements in stress, immunity, or mood.
Some studies suggested possible longer-term benefits such as fewer sickness absences, better sleep, and better quality of life, but the evidence was limited and more high-quality trials are needed.
Deep dive
What the paper is actually saying
Why This Paper Exists
Cold-water immersion has become popular as a general health and wellbeing practice, but its actual effects in healthy adults have not been clear.
What The Authors Wanted To Answer
The authors wanted to find out whether cold-water immersion affects psychological, cognitive, and body-based health outcomes such as stress, sleep, immunity, inflammation, mood, and focus.
How The Study Was Done
This was a systematic review and meta-analysis, meaning the authors searched electronic databases for earlier randomized trials and combined results when possible. They included healthy adults age 18 or older who used cold showers, ice baths, or plunges at 15°C or colder for at least 30 seconds.
What The Study Found
Across 11 studies with 3177 participants, cold-water immersion caused a significant rise in inflammation immediately after exposure, but not at 1, 24, or 48 hours afterward. The pooled analyses did not show significant immediate or 1-hour effects on stress or immune function. In studies summarized without pooling, there were signals of possible longer-term benefits, including a 29% reduction in sickness absence in people taking cold showers, plus improvements in sleep quality and quality of life, while mood did not improve.
Takeaway
The evidence suggests cold-water immersion may have mixed, time-dependent effects rather than a simple overall benefit. It may have some practical uses for wellbeing support, but current evidence is limited by the small number of trials and other study constraints.
Limits
What this abstract does not fully answer
Only 11 randomized trials were included, so the evidence base was small.
The abstract says current evidence is constrained by small sample sizes.
Study populations lacked diversity, which may limit how broadly the findings apply to other groups of people.
Key numbers
Numbers the abstract makes important
11 studies
The review included 11 randomized trials, so the conclusions are based on a relatively small evidence base.
3177 participants
This was the total number of participants across all included studies.
≤15°C for at least 30 seconds
This was the review's definition of cold-water immersion exposure, including cold showers, ice baths, or plunges.
7°C to 15°C
The cold-water interventions in the included studies used temperatures in this range.
30 seconds to 2 hours
The duration of cold-water exposure varied widely across studies.
Mean PEDro score 6.4
On average, the included trials were rated moderate to high quality by the PEDro study-quality scale.
Source abstract
Original abstract sections
OBJECTIVE
This systematic review and meta-analysis aimed to evaluate the psychological, cognitive, and physiological effects of CWI 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 0.05), 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. PROSPERO (ID: CRD42024500591).