Scientists now believe that a hot bath can help to restore the body's natural temperature rhythm – which can be disrupted in people living with depression.
We already know that exercise is a great mood-lifter but this study suggests that regular bathing might be faster acting than hitting the gym in lifting symptoms of poor mental health.
And, of course, having a bath is much easier and more accessible to do than taking a 45-minute spin class.
Depression can leave people totally deflated and unable to exercise, so this is really positive news for anyone who feels like gymming or getting outside is a bit out of their reach.
Experts from the University of Freiburg in Germany tested the effects of thermal baths on 45 people with depression.
"Hyperthermic baths seems to be a fast-acting, safe and easy accessible method leading to clinically relevant improvement in depressive disorder after two weeks," they said.
"It is also suitable for persons who have problems performing exercise training."
The participants had an average age of 48, and had moderate-to-severe depression.
Their depression was scored using the HAM-D scale. A score of 19 or higher counts as "severe" depression; the study's average score was 21.7.
They were randomly assigned to either two spa baths a week, or two sessions of moderate exercise a week, before their depression was retested.
People in the bathing group saw their depression drop an average of six points within two weeks, while the exercise group's only dropped three.
13 of the 23 people in the exercise group also dropped out of the study before the end, while only two of the 22 in the bathing group failed to finish.
All the bathers had to do was sit in a 40'C bath for 30 minutes, then wrap themselves in blankets and hot water bottles for another 20.
In the exercise group, participants had to do 40-45 minutes of moderate aerobic workout, such as running, dancing or swimming.
So why exactly was bathing so effective – apart from the fact that having a good old soak and lie down is a lot more pleasant than a 45-minute run?
Well, it may be down to our circadian rhythm (our inner alarm clock).
Previous studies have found that taking a warm bath before bed can improve sleep because it opens up the blood vessels in the skin – allowing our bodies to get rid of excess heat.
So one possible answer is that the people in the bathing group might have seen an improvement in the quality of their sleep – and depression is known to adversely affect sleep.
It's also believed that depression can interrupt the body's ability to regulate its temperature, so taking regular hot baths could help to correct that, while elevating our levels of serotine (the feel-good hormone) which tends to be low in people with depression.
Of course, exercise is still a proven mood-upper and boasts a tonne of other advantages for everyone (depressed or not), but bathing is a great for anyone who isn't in a position to workout at the moment.
It isn't going to "cure" depression so if you are struggling with your mental health, talk to your GP or a loved one.
Self- care should form part of your arsenal for dealing with poor mental health – but it can't be your only tool.