Common sense would predict that exercise might be beneficial for persons with depression, but since our simple intuitions have not always been confirmed by clinical data, it is nice to see data that say “Yes, your common sense was correct. Exercise is beneficial for depression.”
Cooney et al reviewed clinical trials that compared exercise with either no treatment or a control for study subjects with depression. Because different clinical trials use different depression scales, results from different trials were converted to a single metric to standardize comparisons. To make the outcomes more clinically relevant, degree of change was quantified as small, moderate, or large.
Although not all trials found a favorable effect of exercise on depression — and one trial actually reported a detrimental effect — the meta-analysis of the data found an overall moderate, favorable effect of exercise compared to control, equivalent to an approximately 5-point reduction on the Beck Depression Inventory.
The data were not sufficient to distinguish a particular type (e.g., aerobic vs non-aerobic), intensity, or duration of exercise needed to achieve a favorable impact. Nonetheless, some national guidelines already include recommendations for exercise as a treatment for mild-to-moderate depression (NICE: National Institute for Health and Clinical Excellence Guideline from the United Kingdom). Patients might be more motivated to consider exercise as a respectable treatment if they understand that favorable results are supported by scientific data.