To pamper your morale and stay mentally sharp, you quickly think of yoga, sleep or daylight. However, a British team has tested a method that is the polar opposite of comfort: a few regular minutes in water at 10°C, protocolized and monitored, have been associated with better sleep and a more alert brain, according to data published in the scientific journal Physiology & Behavior.
This habit? The cold bath, or more broadly immersion in cold water. Researchers from the University of Central Lancashire, led by Joseph Knill-Jones and Robert Allan, followed 13 adults for four weeks who immersed themselves three times a week for 10 minutes in water at around 10.4°C. The scientists assessed their mood, anxiety levels, sleep quality and cognitive performance throughout the experiment. Although the exercise is far from comfortable, the results observed have caught their attention.
Cold bath: what the study shows for the brain and mood
The team from the University of Central Lancashire used validated questionnaires such as the Pittsburgh Sleep Quality Index for sleep and the Penn State Worry Questionnaire for worry. The authors report a clear reduction in worrying ruminations after just a few sessions, then a significant improvement in sleep quality from the second week, with an average sleep score which dropped from around 7.8 to 5.7 in the third week.
The brain does not seem to remain insensitive either. Volunteers took tests like the Trail Making Test, which measures processing speed and mental flexibility. As a result, the average time to complete a version of this test increased from around 15 seconds at the start of the study to 11 seconds at week 3. With only 13 participants and not yet large cohorts, these results remain exploratory, but they outline a link between cold bath, reduction in worry and better mental clarity.
Other cold water immersions also improve mood
Another study, published in 2021 and conducted at sea at around 14°C with 42 volunteers, showed that a single immersion of up to 20 minutes reduced feelings of sadness, anger and tension, measured with the Profile of Mood States questionnaire. Participants described a calmer and more positive state immediately after exiting the water.
In 2023, brain imaging research available on PubMed Central observed the effect of just five minutes of cold water immersion. The authors describe both an improvement in affect and changes in brain connectivity measured by functional MRI. Several teams evoke a possible role of an adjustment of cortisol and a reset of the autonomic nervous system, without the mechanisms being yet completely established.
Testing the cold bath without danger for your brain and your health
Before dreaming of frozen lakes, specialists from the Prevention Observatory of the Montreal Heart Institute point out that cold water exposes you to thermal shock, heart rhythm disturbances and hypothermia. People with a history of cardiovascular disease or Raynaud’s syndrome, for example, are among the profiles for whom caution is necessary.
For a gentler first contact, it is recommended to end your shower with 30 to 60 seconds of cool water, then gradually lower the temperature. The data suggests that regular practice, several times a week, could be enough to test the effect on stress, worry and mental clarity, without the need to jump into open water alone in the middle of winter.