Cold showers, immersion and winter swimming are often grouped together as if the evidence points in one direction. A systematic review and meta-analysis published in Frontiers in Physiology on September 16, 2026 found a more uncertain record: several pooled estimates leaned favorable, but the available studies did not establish psychological or clinical benefit. [1]
What was reviewed
The authors searched four bibliographic databases, two trial registries and citation lists under a prospectively registered and published protocol. Thirteen studies involving 4,105 adults met the criteria: five randomized controlled trials, two non-randomized controlled studies, four single-group intervention studies and two observational cohorts. Samples included mostly healthy adults, with some participants who had depressive symptoms, multiple sclerosis or rheumatic disease. [1] [2]
The methods were not one intervention. They included cold showers, chest-level or fuller immersion and winter swimming, at reported temperatures from about 6–7 °C to 20 °C. Sessions ranged from 30 seconds to 15 minutes and from a single exposure to repeated practice across a winter. Some programs also included breathing, mindfulness, swimming or social settings, which makes the effect of water temperature difficult to isolate. [1]
What the pooled results showed
Depressive-symptom results came from six studies and 457 participants. The all-design estimate favored cold-water exposure but crossed the null (Hedges g −0.42, 95% CI −0.99 to 0.14); restricting the analysis to controlled studies reduced it to −0.20 (−0.74 to 0.33). Perceived stress similarly moved from −0.30 (−1.48 to 0.88) across designs to 0.03 (−0.79 to 0.86) in controlled studies. Anxiety showed little consistent signal. Mood or affect leaned favorable, but its confidence interval also crossed the null and the estimate became smaller in controlled-only analysis. [1]
Those intervals are wide enough to include no effect. Standardized scores across different questionnaires also do not show whether any change was noticeable or clinically meaningful.
Why confidence remains low
All five randomized trials received an overall high-risk-of-bias judgment. The non-randomized studies were rated serious or critical risk, and the two cohorts very high risk. Methods, populations, comparators and exposure conditions varied substantially; longer follow-up was uncommon; no formal GRADE assessment was performed; and several outcomes relied on uncontrolled data. Adverse events, screening and safety procedures were reported too inconsistently to establish that self-directed exposure is safe across populations or settings. [1]
Funding, conflicts and our relationship to cold
The review authors reported no financial support and no commercial or financial conflicts. They disclosed using ChatGPT for grammar, English phrasing and coding assistance, with manual review. [1]
Body Mind State is published by BHVD, which also develops The Ice Sack and publishes Cold Shift. [3] This ownership makes the method boundary essential: the review studied water exposure. Its findings do not establish benefits for dry cold containment, local cooling, The Ice Sack or a BHVD protocol. The evidence also does not support cold-water exposure as a stand-alone treatment for depression or anxiety, and this article is not a personal-use recommendation.