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Is Exercise an Antidepressant?

The growing popularity of unconventional approaches to treating depression has fueled interest in the possible antidepressant effects of exercise. Although results from recent meta-analyses have suggested that there may be such effects, the analyses included uncontrolled and nonrandomized studies, pooled studies comparing different sorts of treatments, and did not assess study quality. These researchers performed a meta-analysis of 14 randomized, controlled studies examining the effects of exercise (8 vs. no treatment, 5 vs. cognitive-behavioral therapy [CBT] vs. antidepressants) in depressed adults. The investigators also rated study quality, computed effect size, and did a "meta-regression" to assess the effects of study quality on reported outcomes.

Overall, research quality was found to be mostly poor: Only 3 studies concealed the randomization of patients; only 2 studies performed intent-to-treat analyses; only 2 studies used objective ratings; and only one study achieved a blinded assessment. Nine studies evaluated nonclinical populations, and most studies relied on rating scales rather than structured interviews to assess depression. Although the pooled standardized mean difference in effect size was -1.1, study outcomes were heterogeneous. Effects were much smaller in the few well-designed studies, including those with longer follow-ups. Effect sizes were comparable to those of CBT for the 5 studies investigating both treatments.

Comment: The results of this meta-analysis clearly document the poor quality of exercise studies of depression. Because study participants always exercised in groups or with a coach, a socialization effect also confounded results. Non-motivated subjects were excluded from participation in the studies, and results were never reported as a proportion of patients actually responding. Finally, CBT was not delivered by any standardized method, casting some doubt on the importance of the similar effect sizes associated with CBT and exercise.

— P Roy-Byrne

Published in Journal Watch Psychiatry April 25, 2001

Citation(s):

Lawlor DA and Hopker SW. The effectiveness of exercise as an intervention in the management of depression: Systematic review and meta-regression analysis of randomized controlled trials. BMJ 2001 Mar 31 322 763-767.

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