Physical activity is associated with lower rates of incident depression

Many studies show a general association between greater physical activity and a lower risk for depression. In this meta-analysis, researchers sought to quantify a dose-response relation by evaluating 15 observational studies (190,000 participants with follow-up ranging from 3 to 25 years) with a wide range of activity level measures that could be harmonised into a single measure of marginal metabolic equivalent task hours per week (mMET-h/wk).

A mMET is any non-occupational leisure-time or domestic physical activity incremental to basal daily or work activities. A 1-hour brisk walk would equal about 3.5 mMET-h. Depression was measured as either self-reported physician diagnosis or depression symptoms on a validated screening instrument.

Nearly 80% of participants reported physical activity at levels lower than 17.5 mMET-h/wk at study entry. Compared with patients who reported no incremental physical activity, those who reported at least 4.4 mMET-h/wk (e.g., brisk walking for 1.5 hours weekly) had 18% lower relative risk for depression. The relative risk reduction for 8.8 mMET-h/wk was 25%. An additional benefit was minimal for physical activity beyond 8.8 mMET-h/w.