A number of heath trends tout showering in cold water for a number benefits, from immune boosting effects to increased alertness and weight loss. A study published in Medical Hypotheses suggests cold showers may have an anti-depressive effect.
Depression is hypothesized to result from the convergence of 2 factors: lack of physiological stress and genetic predisposition. The reasoning is that primates have experienced relentless physiological stress such as sudden body temperature changes, and the lack of “thermal exercise” retards brain function.
Researchers from the Virginia Commonwealth University School of Medicine have consistent findings that suggest cold showers can provide the “thermal exercise” that stimulates the brain and counteracts depression:
Exposure to cold is known to activate the sympathetic nervous system and increase the blood level of beta-endorphin and noradrenaline and to increase synaptic release of noradrenaline in the brain as well. Additionally, due to the high density of cold receptors in the skin, a cold shower is expected to send an overwhelming amount of electrical impulses from peripheral nerve endings to the brain, which could result in an anti-depressive effect.
They also evaluated the effects of cold hydrotherapy on a number of patients and found cold hydrotherapy relieves symptoms of depression. They remarked that cold showers have an analgesic effect and no noticeable side effects.
To test the hypothesis, an approach to treating depression is proposed that consists of adapted cold showers (20 °C, 2–3 min, preceded by a 5-min gradual adaptation to make the procedure less shocking) performed once or twice daily. The proposed duration of treatment is several weeks to several months.