Remember that movie, Forest Gump, when, after being hit with a big emotional trauma in his life he started running and didn’t stop running for months or years? Well there might be some support for the use of exercise and even diet for the treatment of depression. (1)
In the case of exercise, analysis of multiple studies have shown a large effect size, especially for mild to moderate depression from an exercise program. One other intriguing study using mendelian randomization showed that compared to a sedentary lifestyle, a strenuous to moderate exercise program for 15 to 60 minutes per day led to a reduction in the development of depression by 26%. Remember that mendelian randomization is a nifty trick of using the random genetic variation of people to allocate treatment and avoid confusing causalities.
In the case of diet and in particular the Mediterranean diet that’s been studied the most, the effect on depression is smaller and more problematic.
Part of the problem for both strategies comes from the fact that obesity causes depression because society dumps a lot of disapproval on obese people and since diet and exercise don’t help weight loss much, the lack of a big effect effect on depression may be caused by that reality.
Major depressive disorder has a lifetime risk of 10 to 15% and the standard treatments of medication and counseling don’t fix as many as a third of sufferers. There are also new drug options but depression still often remains resistant. While we wait for better treatments, diet and exercise are cheap and good for you anyway. But the symptoms of depression are dominated by low energy and motivation, so it is tough to follow through with even these seemingly simple strategies.
1. Kohler-Forsberg O, Cusin C Nierenberg AA. Evolving issues in the treatment of depression. JAMA June 25,2019;321(24):2401-2.