Cold-water exposure and psychological outcomes in adults: a systematic review and meta-analysis.

INTRODUCTION

Cold-water exposure (CWE), including cold showers, cold-water immersion, and winter swimming, is increasingly discussed as a behavioral strategy for improving mood, stress regulation, and mental wellbeing, but clinical evidence remains fragmented.

METHODS

MEDLINE, Embase, PsycINFO, and Web of Science were searched from inception to June 6, 2025, with an update in December 2025. Eligible studies included adults exposed to CWE through cold showers, cold-water immersion, or winter swimming. Randomized, non-randomized controlled, cohort, case-control, and single-group pre-post studies were eligible. Two reviewers independently screened studies, extracted data, and assessed risk of bias. Random-effects multilevel meta-analyses used standardized mean differences, expressed as Hedges g. Sensitivity analyses were conducted where possible.

RESULTS

Thirteen studies including 4105 participants met inclusion criteria. Pooled estimates generally favored CWE for depressive symptoms, perceived stress, wellbeing, and mood or affect, but confidence intervals were wide and several estimates attenuated in controlled-only analyses. Anxiety showed little evidence of consistent benefit. Additional outcomes, including sleep, cortisol, heart rate, and pain, were sparse but generally directionally favorable. Most studies had high, serious, or critical risk of bias.

CONCLUSION

The available evidence does not establish that CWE improves mood, depressive symptoms, perceived stress, wellbeing, or related outcomes. The evidence remains limited, heterogeneous, and at substantial risk of bias, and several estimates became smaller in controlled only analyses. CWE should not currently be regarded as a standalone treatment for psychiatric disorders. Larger controlled trials are needed to clarify clinical relevance, safety, mechanisms, and optimal use.

SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD420250654531.