Cryotherapy – applying ice, cold water, or cold air to the body to promote health – has been practiced for centuries. Indeed, the more-than 3,000-year-old Edwin Smith papyrus, the oldest known surviving scientific writings on spinal injuries, refers to treating spinal trauma with cold-water immersion.

The practice of cold-water immersion certainly has its devotees. But do daily cold plunges, whether it's a cold shower, swimming in a frigid ocean, or sitting in a bathtub filled with ice cubes, really benefit health and well-being? To answer that question, researchers from the University of South Australia (UniSA) undertook the most comprehensive review and meta-analysis yet undertaken on the topic.

"Cold-water immersion has been extensively researched and used in sporting contexts to help athletes recover, but despite its growing popularity among health and well-being circles, little is known about its effects on the general population," said Tara Cain, a research assistant from UniSA's Alliance for Research in Exercise, Nutrition and Activity (ARENA) and the study's lead and corresponding author.

The researchers reviewed and analyzed 11 studies published between 2014 and 2023, comprising a total of 3,177 healthy adult participants. Ten studies looked at immersion in an ice bath or cold plunge, and one studied the effect of cold showers. Studies were only included if participants were immersed in water at or above chest level. Water temperature ranged from 7 °C to 15 °C (45 °F to 59 °F), with immersion times of at least 30 seconds up to two hours. The outcomes of particular interest to the researchers related to sleep, stress, fatigue, energy, skin health, immunity, inflammation, mental well-being, depression, anxiety, mood, concentration, and alertness or focus.

"In this study, we noted a range of time-dependent results," Cain said. "Firstly, we found that cold-water immersion could reduce stress levels, but for only about 12 hours post-exposure. We also noted that participants who took 30, 60, or 90-second cold showers [for 30 days] reported slightly higher quality of life scores. But again, after three months these effects had faded.