Cold Showers in the Morning: A Wake-Up Call for Circulation and Focus

In 2000, Šrámek and colleagues in Prague had young men sit up to their necks for one hour in water at 32, 20 and 14 degrees Celsius. At 14 degrees, blood noradrenaline rose by 530 percent and dopamine by 250 percent, while adrenaline remained unchanged and cortisol tended to fall. What this means for you: cold is a strong signal to exactly the messenger substances associated with alertness and drive. A short shower, however, is a much smaller stimulus than an hour in a cold pool, so the numbers cannot be transferred.

In 2006, Datta and Tipton from Portsmouth described in the Journal of Applied Physiology what happens when the skin is suddenly cooled in water. An involuntary gasp follows, along with a rise in blood pressure and hyperventilation that overrides both conscious and other automatic breathing control. What this means for you: this cold shock response is the main reason why cold water can be dangerous for the inexperienced. Under the shower you can dose it; in the water, often not.

In 2012, Shattock and Tipton described in the Journal of Physiology that submersion in cold water can trigger two opposing reflexes at the same time: the cold shock response with a racing heart and the diving reflex with a slowing heart. They consider this autonomic conflict a possible cause of heart rhythm disorders that can become dangerous in vulnerable people. What this means for you: under the shower your head stays above water, and this double stimulus of submersion does not occur.

In 2015, Buijze and colleagues in the Netherlands randomly assigned 3,018 adults with no experience of cold showering to four groups: 30, 60 or 90 seconds of cold water at the end of a warm shower for 30 days, or a control group. Self-reported sickness absence from work was 29 percent lower in the cold groups, but the number of days of illness did not differ, and no serious adverse events occurred. What this means for you: the everyday stimulus is well tolerated and well studied, but it is not proof of a stronger immune system.

In 2025, Cain and colleagues from Adelaide pooled eleven randomized trials on cold water applications in healthy adults in PLOS ONE, ten of them in a bath and only one under the shower. They found an increase in inflammatory markers directly after the cold, lower reported stress twelve hours later and improvements in sleep quality and quality of life, but no consistent effect on mood. What this means for you: for the body, cold is initially a stress stimulus. What follows may be favorable, but the evidence is still thin.

In 2026, Traylor and colleagues had eleven young athletes take a ten-minute cold shower at 17 degrees Celsius on four consecutive days and measured salivary testosterone before and after. In some, the value rose; in others, it fell; at group level there was no significant change. What this means for you: the idea that cold showers boost hormone production is not supported so far. The study is, however, very small.

In 2026, Hagner-Derengowska and colleagues randomly assigned sixty combat sport athletes to two groups: four weeks of contrast showers after training or a lukewarm shower. After four weeks, resting heart rate in the contrast shower group was a little over two beats per minute lower, heart rate variability somewhat higher and perceived recovery better, but after a two-week break none of this was measurable anymore. What this means for you: temperature stimuli under the shower can measurably engage the autonomic nervous system, but the effects are small and apparently last only as long as you keep at it.

In 2023, Yankouskaya and colleagues examined healthy adults in an MRI scanner before and after five minutes of immersion in 20 degree Celsius water. Afterwards, participants felt more active, more alert, more attentive and less nervous, accompanied by stronger coupling between large brain networks for attention and self-perception. What this means for you: the awake feeling after cold appears to have a neurobiological correlate. What was measured, however, was a bath, not a shower.

In 2008, Shevchuk published the idea in Medical Hypotheses that adapted cold showers might ease depressive symptoms, because cold stimulates the sympathetic nervous system, noradrenaline and beta-endorphin. According to the abstract, the practical testing involved a statistically insignificant number of people without diagnosed depression, and the author himself calls for larger studies. What this means for you: an interesting idea, explicitly a hypothesis. It does not replace treatment.

In 2024, Kunutsor, Lehoczki and Laukkanen summarized the literature on cold water applications for healthy aging in GeroScience. They describe possible effects on cardiovascular risk factors, brown adipose tissue, alertness and mood, but emphasize that the evidence comes mainly from small intervention studies and that the optimal duration and temperature are unclear. What this means for you: the field is promising, but young. Anyone who speaks of established long-term effects today is ahead of the research.

In 2023, Barwood and colleagues analyzed seventeen study groups on habituation to cold shock. After repeated immersion, the rise in heart rate was on average 14 beats per minute lower, minute ventilation about 21 liters per minute lower, and habituation typically appeared after about four exposures. What this means for you: the intense initial reaction weakens considerably with repetition. These data come from immersion studies, but the principle of habituation plausibly carries over to smaller stimuli.

In 2016, Wigley and Flavahan described Raynaud's phenomenon in the New England Journal of Medicine as a disorder of vascular regulation in which cold can trigger excessive narrowing of the blood vessels in fingers and toes. They distinguish the common, usually harmless primary form from secondary forms, which may be caused by an autoimmune disease, for example. What this means for you: if you react to cold with white or blue fingers, have that checked first.

In 2021, Prosty and colleagues from Montreal analyzed studies on cold urticaria and found that about 21 percent of those affected had already experienced an anaphylactic reaction. The authors suggest considering an emergency kit with an adrenaline auto-injector for these people. What this means for you: if your skin reacts to cold with hives, the cold shower is not a self-experiment, but a matter for an allergist.