The moral urgency of a good study on cold showers and depression & anxiety

The potential benefits are huge, the costs are minimal and if it works it could make all the difference for a lot of people

In short- there are really good reasons to think cold showers could help greatly with mood disorders and general happiness, no one has conducted a good study on this yet, and I propose people on the internet self-organize to make a somewhat informal internet study happen. Hopefully this will make the idea of running a study more attractive to medical scientists etc.

Sometimes, a really simple idea has a lot of potential to do good at very little cost. Sometimes fruit can be so low-hanging that no one has bothered to pick it up, because doing so won’t make them look glamorous. I believe this is one of those times.

There’s an article in The Journal of Medical Hypotheses which, as I understand it, is something of a fringe journal. This article proposes a simple treatment for depression- cold showers. This article has 150 citations, unusual indeed for a lowish-impact factor journal. Something about the idea, I think, fascinates people.

Yet as far as I can tell, no one has run a proper experiment on the effect of cold showers on depression and other mood disorders- bizarre given how the idea of a link between cold showers and mood persists in the popular imagination. In what follows, I’ll try to make a case for running a study like this ASAP.

The evidence

Several studies related to the idea of treating depression with cold showers have been conducted. However, there has been no reasonably large study of the impact of cold showers on mood disorders over at least a month.

[The following two paragraphs contain a terrible error. I compared the experimental group at T1 to the experimental group at T2 without cross-comparing the control group at T1 versus the control group at T2 to make sure there wasn’t also a large difference there. I vaguely thought I had done this, but I hadn’t. The real experimental effect appears to be much smaller, although the result is significant. May God have mercy on my soul.]

One study on the effects of cold showers on physical health incidentally included a measure of mental health. The results were promising and the sample was huge (3000 in total). Before the experiment, In the 60-second cold shower group, the median score for mental health was 81 on the SF-36 mental component (scores were seemingly normed to be out of 100). After the cold-shower treatment, the median increased to 85. More significantly, for the 25th percentile, the score increased by 7 points, equivalent to most of the initial gap between the 25^th percentile and the 50^th.

If we can take the SF-36 mental component as a measure of well-being, then this jump, if replicated across the population as a whole, would be equivalent to a large jump in GDP (doubling? According to my back-of-the-envelope calculations). Of course, this won’t happen for many reasons- not least, not everyone will take up cold showers, but as a provocation it is interesting, and the welfare benefits could be large compared to, say, the discovery of a typical new antidepressant.

In general, the effect by percentiles indicated that the worse off one was, the more one benefited. Unfortunately, the study can only hint at possible effects on depression and anxiety, because the sample studied was seemingly extremely mentally healthy. Every group apparently had a median anxiety score of 1/24 (taken separately to the SF-36 mental component), unless I have misunderstood the paper in some way. Still, the pattern of greater increases for the worst off is extremely promising.

A study in thermal biology found a reduction in negative affect, significant despite a very small sample size (16). However, again, this study only looked at immediate effects (up to 180 minutes post-exposure) and did not focus specifically on depressed or anxious patients. Another study with 33 participants found similar, with similar limitations.

Another study found powerful effects on mood of an ocean swimming course, but the sample size was small, and it would be problematic to extrapolate from this study to cold showers- because of the exercise component of ocean swimming, because the swims were less frequent than daily, and numerous other differences between swimming in the ocean and having a cold shower.

There are various other studies, case studies etc., but I’m not aware of any ‘better’ than these, with respect to our objectives. Back-of-the-envelope calculations from the available evidence I’ve linked here (mostly the last study I mentioned, and the first) suggest an average effect size of perhaps about half a standard deviation on mood and depression- which is huge- if a study laser-focused on cold showers and wellbeing, and properly powered, can replicate it. This could- no exaggeration- give a lot of people their lives back if it works.

Why run a cold-shower study

Although nothing is established, in my view the case for potential benefits is strong

• There is a lot of folk wisdom (something I take very seriously in relation to topics of psychological health) proposing that cold showers may improve mood.

• Similarly, I know of anecdotes of success, including in my case. r/coldshowers is full of them.

• There is a clear potential mechanism- viz, the effect of Adrenaline. In fact, there are several potential mechanisms.

• As noted, the preliminary results which are available suggest that it might work.

• Access to cold water is very common around the world.

• If we could establish that cold water has even a small impact on depression and anxiety, hundreds of millions of people could access, essentially for free, some degree of alleviation of terribly painful conditions. If the effect is moderate or large the consequences for human welfare could be enormous.

The low costs are also attractive.

• A study on the efficacy of cold showers for treating depression would cost, nothing or almost nothing.

• A preliminary study, at least, could probably be organized by people on the internet, without a professional background (although medical advice on risk minimisation is strongly advisable).

Making this happen

I reckon this study could be run informally by recruiting people on the internet, thus encouraging medical scientists to get a move on and do the study in a more formal way for publication in a journal and consumption by the medical community.

Anyone with a large following, or with the determination to gather one, and a moderate understanding of methodology could do it. Medical advice on how to minimize risk is necessary before proceeding- the chance of mortality due to cold showers is minimal, but no one wants this on their conscience.

Materials

I would recommend:

1.            A quality-of-life instrument

2.            A measure of depression focused on emotional and cognitive symptoms (e.g. the DMI-10)

3.            A measure of depression including both physical and mental symptoms (e.g. the Beck-depression inventory)

4.            A measure of anxiety (e.g. the ASQ)

Participants

Ideal participants would be depressed and/or anxious but given the nature of recruiting for an online study, we might as well recruit healthy individuals and study the effects on them as well as depressed and anxious individuals.

Protocol for cold showers- some incomplete thoughts

I’d suggest consulting with people who are using cold showers a folk remedy for their advice on the ‘optimal’ cold shower, while keeping in mind that the process may have to be ‘wound back’ a bit from the enthusiasms of its most enthusiastic followers because a good compliance rate, and low dropout rate are necessary.

Much of the folk wisdom on this topic suggests that the initial shock of cold is very important. This was the consensus on R/coldshowers when the matter came up, for example. Plausibly, cold shock, and not just gradual exposure to cold, is important for the adrenal response. Thus in order to test the strongest possible version of the hypotheses I suggest the following protocol:

The participant stands outside the region where the water will fall, turns the tap to the coldest it will go, and then turns that tap on at a high volume (higher volume will result in more coverage of the body and thus a greater experience of coldness). The participant waits 5 seconds to ensure that the water is fully cold (longer if necessary) than steps into the water.

The participant should try to let cold water cover every part of their body, including the back, neck, and other parts that cause a feeling of ‘shock’ to maximize, again, so as to maximize the adrenal (and other physiological) responses.

How long? The large Dutch study discussed earlier used a maximum period of 90 seconds. The r/coldshowers subreddit recommends 5 minutes (300 seconds). Naturally, whatever period is chosen, participants should time themselves, perhaps with the stopwatch on their mobile phones.

Some participants do not feel clean after a cold shower, and many people regard a hot shower as an attractive pleasure, hence, for the sake of compliance, I’d recommend letting participants have a hot showers before, after, or during another part of the day.