Contrast therapy boosts your energy and mood

In the studies that have tested it, alternating heat and cold was followed by small, short-lived changes in how people said they felt, not by lasting changes in mood or energy. In the largest trial, 3,018 working adults in the Netherlands ended their usual hot shower with 30, 60 or 90 seconds of cold water every day for a month. After 30 days their scores on the mental health part of a quality-of-life questionnaire were slightly higher than those of people who showered as usual (medians of about 85 against 84 out of 100), a difference the authors judged too small to matter clinically, and by 90 days it was no longer significant. Anxiety scores were the same in every group. Having more energy was the benefit people in that trial described most often, many comparing it to caffeine, but it came from their own comments and was not measured against the group that showered as usual.

Most of the other research, about two dozen small studies, asked athletes how tired or how recovered they felt after hard exercise, which is a different thing from everyday tiredness. A 2017 analysis of 23 team-sport studies of cold and contrast water found that fatigue ratings one to two days later favoured contrast water, while ratings of muscle soreness did not. In a 2026 trial, 60 combat sport athletes took a contrast shower or a lukewarm shower after every training session for 4 weeks. Self-rated recovery rose in both groups and about 0.6 points more with contrast showers on a 6 to 20 scale, and two weeks after the showers stopped the groups no longer differed. In 15 male college swimmers, tiredness ratings after hard sprints were lower following contrast water than following rest (6.6 against 7.6 on a rating line), and their 100 metre times did not improve. In 13 men after weight training, neither contrast water nor cold water changed fatigue ratings over the next four hours. In every study people knew which routine they had, so expectation may explain part of what they reported, and no study of alternating heat and cold tested people with depression or long-lasting tiredness.

Outside sport, studies of alternating heat and cold and how people feel are few. In one, 10 people who already used saunas did three rounds of 10 minutes in a sauna at 85 to 90 degrees C, 1 to 2 minutes in a 16 degrees C bath and 7 minutes of rest, while 10 others rested and took a 37 degrees C bath. On rating scales, the sauna group reported feeling more relaxed and more intense pleasure across the rounds than the comparison group. The paper does not say how people were assigned to groups, and all four authors worked for the company that paid for the study, which declared a related patent and products in development. The shower trial recruited adults aged 18 to 65 through advertising and social media, excluded people with serious heart, lung or other disease, and collected everything through online questionnaires, so whether people actually took the cold showers could not be checked. 79 percent reported finishing the month and 64 percent kept going afterwards. The most common unwanted effect was feeling cold in the body, hands or feet, reported by up to 13 percent. The trial was entered in the Dutch trial register after it had run, before its data were analysed. Its main result was 29 percent fewer self-reported sick days; the number of days people felt ill did not change.

Research on cold water alone is larger and has been pooled. A 2026 review combined 13 studies of cold showers, cold baths and winter swimming with 4,105 people, most of them from the Dutch shower trial. Its pooled figures leaned toward better mood and fewer depressive symptoms, but the ranges were wide and included no effect, the figures shrank when only studies with a comparison group were counted, and anxiety showed no consistent change. Its authors concluded that the evidence does not establish that cold water improves mood, and that it does not support cold water as a treatment on its own for depression or anxiety disorders. They rated most of the studies at high risk of bias. A 2023 review of 20 randomised trials of Kneipp hydrotherapy, a German water treatment built mostly on cold water applications, found 21 comparisons on mental health outcomes such as anxiety and depression: 8 favoured the water treatment, 6 leaned toward it without reaching significance, and 7 found no difference. The trials were too different to pool, and their risk of bias was mostly unclear.

Cold water sets off a strong response from the nervous system. In a 2000 study of young men sitting in 14 degrees C water for an hour, blood noradrenaline rose by 530 percent and dopamine by 250 percent. These are chemical messengers linked to alertness, but the study measured blood, not mood, and contrast routines use cold spells of seconds to minutes. Contrast therapy combines two exposures with reported effects on the heart. A review of sudden cold water submersion describes heart rhythm disturbances, including in healthy volunteers, particularly when the face goes under. A review of sauna bathing names unstable angina, a recent heart attack and severe aortic stenosis as reasons to avoid sauna heat, and reports that alcohol during sauna use raises the risk of low blood pressure, abnormal heart rhythm and sudden death. None of the mood or energy studies reported on heart rhythm disturbances. The shower trial excluded people with serious heart or lung disease and the 4-week athlete trial excluded people with known heart, nerve or metabolic disorders. The individual trials described here enrolled adults no older than 65, and none reported on pregnant participants.

The US National Library of Medicine lists feeling very tired among the symptoms of depression, names medicines and talk therapy as its main treatments, and notes that some medicines and conditions such as thyroid problems can cause symptoms that look like depression. None of the studies here tested contrast therapy in people with depression, so they do not show how it compares with those treatments or whether it adds anything to them.