Eighty-four midlife women. Three weeks of daily cold showers. The first randomised controlled trial designed to test whether cold therapy helps women’s depression. The result everyone expected was a clear win for cold. That is not what happened.
The 2024 trial, led by Robin Blades at UCLA’s Department of Psychology, randomised women into two groups: one practised the Wim Hof Method (fast breathing followed by cold showers), and the other did slow breathing followed by warm showers. After three weeks, both groups reduced their depression scores by 24%, and cold did not beat warm on the primary outcome.
That finding could easily kill the conversation, but it shouldn’t — because buried in the daily diary data was a second result, one that the headline measure missed entirely. The cold group showed a significant reduction in rumination after stressful events. Rumination is the tendency to mentally replay and loop on negative experiences, and it is not just a symptom of depression — it is the cognitive pattern most strongly linked to why women develop depression at roughly twice the rate of men. The study didn’t prove cold therapy fixes women’s depression, but it found something more precise: cold appears to interrupt the specific mental process that makes women vulnerable to depression in the first place.
Why women-specific research matters here
Women are diagnosed with depression at about double the rate of men, yet most cold therapy research has been conducted on men, often in athletic contexts, and the question of whether cold has a specific benefit for women’s mental health has largely gone unasked in formal research. The Blades trial was designed to change that: it recruited midlife women facing convergent stressors, hormonal transition, caregiving load, career pressure, and a documented peak in depressive vulnerability. It did not treat women as a subgroup; it centred them.
What the trial tested
The cold group performed fast-paced breathing for several minutes, then stood under a cold shower, building from 15 seconds in the first week to 90 seconds by the third. The warm control group performed slow, calming breathing followed by a warm shower of the same duration, and both groups received audio-guided instructions at home.
There was no untreated control, so neither group represented a baseline of doing nothing; both were engaged in a structured daily ritual involving breath, attention, and water. The question was specific: does adding cold exposure and activation-style breathing produce a greater reduction in depressive symptoms than a warm, calming equivalent? Participants completed standard depression, anxiety, and stress questionnaires before and after the intervention, and filled out daily diaries tracking mood, stressful events, and rumination.
The headline result: cold did not win
Both groups improved: depression scores dropped by 24% across the board, and anxiety, stress, and cortisol reactivity followed the same pattern. Cold was not superior to warm on any primary outcome.
For anyone hoping cold therapy would prove itself as a depression treatment in the cleanest possible test, this is a difficult result. The most rigorous trial to date, designed specifically for women, found that a daily ritual of breathwork and water exposure reduced depressive symptoms regardless of temperature.
But it is not the full story.
What cold did differently: the rumination finding
The daily diary data revealed something the summary questionnaires missed. On days when participants experienced stressful events, the cold group showed a significant reduction in rumination compared to the warm group. This was not a general mood difference; it was specific to the cognitive response that followed stress.
Psychologists distinguish two forms of repetitive self-focused thought: reflection is purposeful analysis that can lead somewhere useful. Brooding is the loop without an exit: replaying what went wrong, rehearsing what you should have said, circling the same thought without resolution. The cold group’s diary entries showed that this loop was disrupted. After a difficult day, they were less likely to fall into it. The warm group, despite their equivalent improvement in overall scores, did not show this specific change.
Why would cold produce this effect when the warm practice did not? Elissa Epel, Professor and Vice Chair of Psychiatry at UCSF and senior author on the study, frames it through hormesis: the principle that brief, controlled exposure to a stressor can build resilience to future stress. “Short-term stress training may elevate positive mood and make us less vulnerable to feeling anxious or depressed when stressful things happen in our life,” Epel explains. The cold shower is a voluntary, time-limited confrontation with discomfort, and the warm shower is pleasant. Both involve breathing and attention, but only the cold version asks the nervous system to manage an acute stress response and come through the other side. That rehearsal, Epel’s work suggests, may be what recalibrates the stress-to-rumination pathway.
Why this matters more than a mood boost
The reason the rumination result is not just interesting but structurally important lies in the gendered architecture of depression itself.
A meta-analysis of 59 studies involving over 14,000 participants, conducted by Johnson and Whisman in 2013, found that women score consistently higher than men on rumination, including both brooding and reflection. The effect sizes were modest individually but persistent across studies and age groups. Women do not simply experience more depression. They engage more in the cognitive pattern that drives and maintains it.
A 2025 network analysis published in Archives of Women’s Mental Health sharpens this further. Brooding functions as a central bridge node in women’s depression networks: the mechanism through which other symptoms connect and reinforce each other. Remove brooding from the network, and the structure weakens. Leave it in place, and it holds the depressive pattern together.
This is the context that makes the Blades finding the study’s most distinctive contribution. Cold showers did not reduce depression scores more than warm showers. But they reduced the specific cognitive mechanism most implicated in why women get depressed in the first place, one that sits at the structural centre of how depression sustains itself in female populations. The trial did not find a better antidepressant, but it may have found a better anti-ruminant.
Three months later: the durability question
One limitation of the Blades trial is its three-week duration. Depression is a chronic, relapsing condition, and a short-term improvement does not tell you whether the benefit holds.
A 2025 follow-up trial led by Epel, with 141 women randomised across four groups (mindfulness, slow breathing with warm showers, Wim Hof Method, and high-intensity interval training), offers early evidence. All four interventions improved depression and stress outcomes. But in the “as treated” analysis, which looks at participants who completed their assigned practice, the Wim Hof group showed better maintenance of depression reduction at three months.
This is not a clean finding. “As treated” analysis is weaker than intention-to-treat because it introduces self-selection bias: perhaps the women who stuck with the cold practice were already more resilient. But it raises a possibility that fits the rumination data. If cold’s distinctive benefit is not acute mood improvement but interruption of a cognitive vulnerability, its advantage might appear exactly where the Epel data suggests: not in the initial weeks, but in sustained reduction of the patterns that drive relapse.
What we still do not know
The Blades trial had no untreated control. Both groups improved by 24%, which could reflect genuine benefit, regression to the mean, expectancy effects, or any combination. We cannot say with certainty how much of the improvement came from the practice itself.
The cold group had an adherence problem: all six dropouts came from the cold group, because cold is genuinely harder to stick with. The first month is where most beginners stop; those who persist past three months tend to build the habit for good. The study’s attrition mirrors this pattern.
The study used showers, not immersion, and full-body immersion adds hydrostatic pressure and a more complete temperature challenge. Whether immersion would produce a stronger rumination effect is plausible but unproven. What is encouraging is that the benefit appeared from showers alone, the most accessible form of the practice.
And the study was conducted during COVID-19, at home, with audio guidance and no social support. The adherence difficulty may partly reflect the challenge of maintaining a hard new habit in isolation, something that guided introduction and community context might help address.
Dr Mark Harper, a consultant anaesthetist who directs Mental Health Swims and is among the most respected clinical voices on cold water and mental health, puts the current position honestly: “For now, we have a very strong base, but not hard evidence, that cold-water immersion is effective for mental health.”
What this means in practice
If you are a woman experiencing depression, the responsible statement is direct: cold therapy is not a substitute for professional treatment. If you are in distress, speak to a clinician, this is not a disclaimer, and it is genuinely important.
Within that boundary, here is what the evidence supports. A daily ritual of intentional breathing and water exposure reduced depressive symptoms by 24% over several weeks, whether the water was cold or warm. The act of showing up and breathing with purpose has value in itself. Cold adds a specific layer: a reduction in the tendency to ruminate after stressful days, which is the cognitive pattern most consistently linked to women’s higher rates of depression. The benefit is not a general mood lift but a more targeted interruption of a specific vulnerability.
Sticking with the practice is the hardest part, and the study’s own dropout data confirms it. Starting with brief cold exposure and building gradually following a cycle-synced approach is not just comfortable advice — it reflects what the trial itself did.
The finding that deserves attention
The first clinical trial of cold therapy for women’s depression did not deliver a simple victory. What it delivered was a finer distinction: cold did not outperform warm for overall depression scores. But on the days that tested participants most, cold changed how they responded. The loop that pulls women back into depressive thinking, the rehearsal of what went wrong, the inability to put the day down, was quieter in the cold group.
Depression is often described as a mood disorder, but for many women it may be better understood as a rumination disorder, a pattern of thought that mood follows. If cold’s value turns out to be not in lifting mood directly but in loosening that pattern’s grip, the first trial will have pointed toward something more useful than the headline result it failed to produce.
