Whole-body cryotherapy

For recovery after exercise, a Cochrane review found only four small trials, in 64 mostly young men. Soreness was a little lower an hour after cryotherapy, but later results were uncertain, and the evidence was rated very low quality [1]. No trial in that review compared it with an ice bath or cold water.

For mood, the evidence is more promising but still early. In a sham-controlled trial, 10 sessions added to medication improved depression scores more than exposure to milder cold [2]. A meta-analysis of 10 studies found large improvements in depressive symptoms, but most studies were small, varied widely and were run by a few research groups [3]. Reviews suggest it may help as an add-on for inflammatory conditions such as rheumatoid arthritis, while calling study quality generally low [4].

No study has tested whether cryotherapy slows aging or extends life in people. It has no approved medical use in the United States. A review of reported harms found 16 adverse events, many of them from nitrogen-cooled cabins that leave the head outside rather than true whole-body chambers [5].

• The FDA has not cleared any whole-body cryotherapy device to treat a medical condition, and in 2016 it warned that health claims for these chambers lack evidence.
• Risks include frostbite and cold burns, especially with damp skin, socks or clothing, and eye injury from the extreme cold.
• Cabins cooled with liquid nitrogen can lower the oxygen in the air around the face, so nobody should use one alone or unsupervised.
• People with uncontrolled high blood pressure, heart or circulation disease, Raynaud's or cold sensitivity, or who are pregnant should not use it without medical advice.
• Trials are small and short, so the effects of frequent sessions over years are unknown.