No Finnish study has shown that cold water "permanently eliminates" depression. To date, no trial has proven that cold baths or cold water swimming treat depression, and a meta-analysis published in September 2026 concludes that they are not a treatment in their own right. What we know comes down to a few physiology studies, one case report, small trials and well-documented risks.
- The viral claim: a University of Helsinki study in JAMA Psychiatry, with 65% remission at 12 months. It cannot be found.
- What exists: one case report (2018), a Danish feasibility study of 13 patients, a few trials in volunteers and two meta-analyses (2025, 2026) with no established effect on depression.
- The risks: cold shock, heart rhythm problems, drowning.
- If you are being treated: never change a treatment without talking to your doctor.
The "Helsinki study" cannot be found
According to the post, researchers at the University of Helsinki proved in JAMA Psychiatry that cold water eliminates chronic depression. A search of the Europe PMC database finds no cold water or swimming trial published by that journal between 2020 and 2026.
The closest Finnish project is a modest one. The University of Jyväskylä scheduled, from October 2023 to June 2024, a short group psychotherapy combined with winter swimming at the Allas Sea Pool in Helsinki, for 16 people with anxiety or depression, compared with 16 people who had the same psychotherapy without swimming. The project page reports no results. A 2023 pilot study (8 young adults, no comparison group) exists only as a preprint.
What the physiology studies measure
Cold water does trigger a strong bodily response. In 2000, a Czech team (Srámek et al.) immersed young men up to the neck for one hour in water at 14 °C: blood noradrenaline rose by 530% and dopamine by 250%. The study did not measure mood. In 2008, a Finnish team (Leppäluoto et al.) followed two groups of 10 healthy women for 12 weeks: 20 seconds of swimming in water at 0 to 2 °C, or 2 minutes of cryotherapy at -110 °C, three times a week. Noradrenaline doubled or tripled after each session; the abstract reports no rise in endorphins. The study looked for hormonal factors that might explain the pain-relieving effect of cold, not an effect on depression.
Some antidepressants act partly on noradrenaline. But a brief rise in the blood is first of all a stress response, not proof of an antidepressant effect. A 2020 review even notes that ordinary exercise, without the cold, would most probably have the same effect.
A 2023 brain imaging (fMRI) study placed 33 healthy adults in a 20 °C bath for 5 minutes: afterwards they felt more alert and less nervous, and some brain connections changed. With no comparison group and no depressed participants, it measures mood in the moment, not depression.
The 2018 case: a real story, but a single case
The best-known case was published in 2018 in BMJ Case Reports by the doctor Christoffer van Tulleken and a team from the University of Portsmouth. A 24-year-old woman, eight months after giving birth, had depression and anxiety diagnosed at age 17. Her symptoms had not improved with two antidepressants in turn (fluoxetine, then citalopram) or with talking therapy, and she wanted to stop medication.
From April to September, she swam in open water once or twice a week, always accompanied. Her mood improved right after each swim. Her medication was reduced after one month and stopped after four months, with medical care provided by one of the authors. At three months she no longer met the criteria for major depression; a year later she was still off medication and free of symptoms.
This case does not prove that cold treats depression. The authors stress it themselves: swimming also brings exercise, nature, company and the pride of meeting a challenge, and all explanations remain hypotheses "supported by anecdotes". As for the follow-up study "Harper 2022", sometimes cited with this case, it cannot be found.
What the trials and meta-analyses say
In January 2025, an Australian team (Cain et al., PLoS One) pooled the randomised trials in healthy adults: 11 studies, 3,177 participants, 3,018 of them in a single cold shower trial. Result: less stress 12 hours after immersion, slightly better sleep and quality of life, but no effect on mood, which only one trial of 20 men had measured. For the authors, the claimed benefits remain "unsubstantiated".
In September 2026, a team at the Charité in Berlin (Ngandeu Schepanski et al., Frontiers in Physiology) included every type of study: 13 studies, 4,105 participants. For depressive symptoms (6 studies, 457 people), the estimate leaned towards a reduction but was not statistically significant, and it shrank further when only controlled studies were kept. Most studies were at high risk of bias. The conclusion: nothing establishes that cold water improves depressive symptoms, and it should not be seen as a treatment in its own right for psychiatric disorders.
A 2024 US trial (Blades et al.) shows why. In 84 women with high stress and high depressive symptoms, three weeks of the Wim Hof method (fast breathing and cold showers) did no better than slow breathing with warm showers: symptoms fell just as much in both groups. All six dropouts came from the cold water group.
In patients, the data are thin. In Denmark, a feasibility study (2023) offered people treated for depression two supervised winter swims a week. Of 13 recruited, 5 took part regularly, all after a medical check. The authors conclude that supervised swimming is possible and safe; well-being and sleep improved in the 5 regular participants, with no comparison group.
In England, the OUTSIDE feasibility trial (8 open water swimming sessions on top of usual care) showed that a large trial could be run, without being designed to measure effectiveness. The OUTSIDE 2 trial, funded by the UK's National Institute for Health and Care Research (NIHR), plans to include 480 adults with major depression, with the PHQ-9 as its main outcome, qualified lifeguards, and the exclusion of people with a history of serious heart problems. Its results are not yet known.
The risks: cold water is not harmless
The main danger comes the moment you enter the water: cold shock. You gasp involuntarily, then your breathing races out of control; your heart speeds up and your blood pressure rises. The response peaks at around 30 seconds and fades over about two minutes. If your head goes under at that moment, very little inhaled water is enough to start drowning. According to a 2020 review, this phase is the most dangerous and may account for most deaths from cold water immersion. It can occur in water as warm as 25 °C: in the 2023 imaging study, every participant had a cold shock response at 20 °C.
- The heart: in people with heart disease, known or not, cold can trigger rhythm problems, sometimes cardiac arrest.
- Hypothermia: the longer you stay in, the more your body cools and the harder it is to move. Alcohol speeds it up.
- Medical advice first if you have: heart or blood vessel disease, Raynaud's phenomenon, cold urticaria, poorly controlled asthma, very low body weight (contraindications cited by the authors of the 2018 case or by the OUTSIDE 2 trial).
- Never alone: in the 2018 case, the Danish study and the OUTSIDE trials, swims were accompanied or supervised. Do not dive or jump in: having your head under water during the gasp is the riskiest moment.
- Your treatment: never reduce or stop a treatment on your own, even if you feel better. In the 2018 case, the reduction was done with a doctor.
If you are going through depression
Depression can be treated, whether mild, moderate or severe, the World Health Organization reminds us: psychological treatment comes first, combined if needed with medication in moderate or severe depression. If cold water appeals to you, talk to your doctor: it can go alongside care, not replace it. The WHO also advises regular exercise, even just a short walk.
To take stock, the PHQ-9 is a nine-question self-assessment questionnaire. Its score is not a diagnosis, but it can help you start the conversation with a professional. See also Treating Insomnia to Ease Depression, Circadian Depression: What the New Body-Clock Study Shows and, in men, the signs of depression that often go unnoticed.
If you are having thoughts of suicide, you are not alone. In the US, call or text 988; in the UK and Ireland, call Samaritans free on 116 123; elsewhere, call your local emergency number.
Frequently asked questions
Why do people feel good after a cold plunge?
Studies in volunteers report more energy and less nervousness right afterwards. But these effects are measured in the moment: they do not tell us whether an improvement lasts, or whether it treats depression.
Is there a recommended temperature or duration?
No. No trial has established a "dose" for mood: studies range from 20 seconds near 0 °C to one hour at 14 °C. Programmes presented online as validated are not backed by any such trial.
I take an antidepressant: can I try it?
Talk to your doctor first, who can check there is no contraindication, especially for your heart. Never swim alone, and do not change your treatment without your doctor's advice.
References: Cain T, Brinsley J, Bennett H, Nelson M, Maher C, Singh B (2025). Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis. PLoS One 20(1):e0317615, published 29 January 2025. doi:10.1371/journal.pone.0317615 (systematic review and meta-analysis of randomised trials, 11 studies, 3,177 healthy adults) | Ngandeu Schepanski S, Batta F, Schröter M, Ngoumou GB, Koch AK, Seifert GJ (2026). Cold-water exposure and psychological outcomes in adults: a systematic review and meta-analysis. Frontiers in Physiology 17:1926423, published 16 September 2026. doi:10.3389/fphys.2026.1926423 (systematic review and meta-analysis, 13 studies of all designs, 4,105 participants) | Blades R, Mendes WB, Don BP, et al. (2024). A randomized controlled clinical trial of a Wim Hof Method intervention in women with high depressive symptoms. Comprehensive Psychoneuroendocrinology 20:100272. doi:10.1016/j.cpnec.2024.100272 (randomised trial, 84 women) | van Tulleken C, Tipton M, Massey H, Harper CM (2018). Open water swimming as a treatment for major depressive disorder. BMJ Case Reports 2018:bcr2018225007. doi:10.1136/bcr-2018-225007 (case report, one patient) | Hjorth P, Sikjær MG, Løkke A, Jørgensen AM, Jørgensen N, Kaasgaard DM, Rasmussen MRV (2023). Cold water swimming as an add-on treatment for depression: a feasibility study. Nordic Journal of Psychiatry 77(7):706-711. doi:10.1080/08039488.2023.2228290 (open-label feasibility study, 13 patients) | Srámek P, Simecková M, Janský L, Savlíková J, Vybíral S (2000). Human physiological responses to immersion into water of different temperatures. European Journal of Applied Physiology 81(5):436-442. doi:10.1007/s004210050065 (experimental study in young men) | Leppäluoto J, Westerlund T, Huttunen P, Oksa J, Smolander J, Dugué B, Mikkelsson M (2008). Effects of long-term whole-body cold exposures on plasma concentrations of ACTH, beta-endorphin, cortisol, catecholamines and cytokines in healthy females. Scandinavian Journal of Clinical and Laboratory Investigation 68(2):145-153. doi:10.1080/00365510701516350 (2 groups of 10 women, 12 weeks) | Yankouskaya A, Williamson R, Stacey C, Totman JJ, Massey H (2023). Short-Term Head-Out Whole-Body Cold-Water Immersion Facilitates Positive Affect and Increases Interaction between Large-Scale Brain Networks. Biology 12(2):211. doi:10.3390/biology12020211 (33 adults, pre-post design without a control group) | Knechtle B, Waśkiewicz Z, Sousa CV, Hill L, Nikolaidis PT (2020). Cold Water Swimming-Benefits and Risks: A Narrative Review. International Journal of Environmental Research and Public Health 17(23):8984. doi:10.3390/ijerph17238984 (narrative review) | Massey H, Denton H, Burlingham A, et al. (2023). OUTdoor Swimming as a nature-based Intervention for DEpression (OUTSIDE): study protocol for a feasibility randomised control trial comparing an outdoor swimming intervention to usual care for adults experiencing mild to moderate symptoms of depression. Pilot and Feasibility Studies 9:122. doi:10.1186/s40814-023-01358-3 (protocol, 88 planned participants) | Massey H, Denton H, Burlingham A, et al. (2025). OUTSIDE: OUTdoor Swimming as a nature-based Intervention for DEpression: a feasibility randomised controlled trial. Mental Health and Physical Activity 29:100723. doi:10.1016/j.mhpa.2025.100723 (feasibility randomised trial, adults with mild to moderate depression) | Massey H, Denton H, Bibby-Jones AM, et al. (2026). OUTSIDE 2: Outdoor swimming as a nature-based intervention, offered in addition to usual care, compared to usual care alone, in people with depression: A study protocol for a randomised controlled trial and economic evaluation. NIHR Open Research 6:84, published 6 July 2026. doi:10.3310/nihropenres.14073.1 (randomised trial protocol, 480 planned participants) | Airo RM, Lehtonen M (2023). Can winter swimming improve mental wellbeing? PsyArXiv, preprint not peer reviewed (8 participants) | University of Jyväskylä: Mental well-being from the cold (project page) | WHO: Depressive disorder (depression) (11 September 2026) | 988 Suicide & Crisis Lifeline | Samaritans: contact us