The Effect of Exercise in Clinically Depressed Adults

Abstract

To assess the effectiveness of exercise in adults with clinical depression. The databases CINAHL, Embase, Cochrane Database of Systematic reviews, Cochrane Controlled Trials Register, MEDLINE, and PsycINFO were searched (1806-2008) using medical subject headings (MeSH) and text word terms depression, depressive disorder and exercise, aerobic, non-aerobic, physical activity, physical fitness, walk*, jog*, run*, bicycling, swim*, strength, and resistance. Randomized trials including adults with clinical depression according to any diagnostic system were included. Two investigators evaluated trials using a prepiloted structured form. Thirteen trials were identified that fulfilled the inclusion criteria. Eight had adequate allocation concealment, 6 had a blinded outcome, and 5 used intention-to-treat analyses. The pooled standardized mean difference (SMD) calculated using a random-effects model was -0.40 (95% CI, -0.66 to -0.14), with evidence of heterogeneity between trials (I(2) = 57.2%, P = .005). There was an inverse association between duration of intervention and the magnitude of the association of exercise with depression (P = .002). No other characteristics were related to between-study heterogeneity. Pooled analysis of 5 trials with long-term follow-up (ie, that examined outcomes beyond the end of the intervention) suggested no long-term benefit (SMD, -0.01; 95% CI, -0.28 to 0.26), with no strong evidence of heterogeneity in this pooled analysis (I(2) = 23.4%, P = .27). There was no strong statistical evidence for small study bias (P > .27). Only 3 studies were assessed as high quality (adequately concealed random allocation, blinded outcome assessment, and intention-to-treat analysis). When we pooled results from these, the estimated beneficial effect of exercise was more modest (SMD, -0.19; 95% CI, -0.70 to 0.31) than the pooled result for all 13 studies, with no strong evidence of benefit. Our results suggest a short-term effect of exercise on depression: on average, depression scores 0.4 of a standard deviation lower in clinically depressed patients randomly assigned to an exercise intervention at the end of that intervention compared to those randomly assigned to a none exercise group. There is little evidence of a long-term beneficial effect of exercise in patients with clinical depression.