3018 people took daily cold showers for 30 days for at least 30 seconds.
Participants who took a cold shower recovered faster from flu than those who didn’t. But they did get sick as often as the rest of society.
Work productivity and levels of anxiety didn’t increase. But the participants experienced other benefits like higher energy levels.
Citation: Buijze GA, Sierevelt IN, van der Heijden BCJM, Dijkgraaf MG, Frings-Dresen MHW (2016) The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial. PLoS ONE 11(9):