Resolves positively if, by my estimation, there is convincing evidence that cold showers are an effective treatment for depression by 2030. There is currently some evidence- theoretical and empirical- for an effect, but there is a paucity of large studies specifically on the effect of showers on depression.
I will consider the effect of cold showers demonstrated if there are at least two peer-reviewed experimental studies random allocation to conditions showing a statistically significant (or Bayesian equivalent) effect on depression which is, in my view, large enough to be clinically significant.
Especially given the low cost of the treatment, the bar to being considered clinically significant is not especially high- for example, if 30% of participants fell below the cutoff for depression in the treatment condition, and only 20% in the control condition, I would consider that clinically significant.
Although multiple controlled studies in a peer-reviewed journal are the most likely route to a positive resolution, I might accept other evidence at my discretion- for example, a single study large and rigorous enough that I consider it decisive on its own.
I will not bet in this market.
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@ADings Yeah, if it starts to look like duelling studies on both sides I am just going to have to use my best judgement. My prejudice is that if there are well-designed, well-powered negative trials, the positive trials are more likely to have made any error, but I'll think through this if we come to it.
I'll chuck something out there which makes me think Cold Showers probably do work for depression (although whether on a clinically significant level, I'm unsure) this highly powered study provides some evidence that showers are good for mental wellbeing, especially for those in the 25th percentile and below:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5025014/
I discuss more evidence more broadly here:
https://philosophybear.substack.com/p/the-moral-urgency-of-a-good-cold