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HealthDay News -- Evidence on the benefits of exercise in treating depression remains inconclusive, results of a Cochrane review indicate, despite the availability of new data from more clinical trials on the topic conducted since the previous analysis in 2009.
Exercise had a moderate effect on depression symptoms in the meta-analysis, but the benefits became less pronounced and were not statistically significant when the analysis was limited to well-designed studies only, Gillian E. Mead, MB BChir, MD, of the Royal Infirmary in Edinburgh, Scotland, and colleagues reported in the Cochrane Database of Systematic Reviews.
Exercise was associated with a treatment effect of -0.62 on depression symptoms when compared with no treatment or control interventions, but many of the 35 trials included in the analysis had one or more biases or faults, the researchers noted. Despite the moderate benefit, the true "effect of exercise may only be small."
In trials that compared exercise with psychological or drug therapy, there were no differences between treatment groups; however, the number of trials reporting these types of comparisons, as well as the number of participants, were both small.
Both the National Institute for Health and Clinical Excellence in England and the Scottish Intercollegiate Guidelines Network have issued guidelines recommending structured, supervised exercise programs consisting of three 45 minute to one hour sessions per week as nonpharmacologic treatment options for depression, according to background information in the article.
To better understand the effects of exercise on depression symptoms, Mead and colleagues searched multiple databases and identified 39 trials involving 2,326 adults that evaluated exercise interventions for depression compared with no treatment or a comparator intervention. A total of 37 of the studies were deemed suitable for inclusion in the meta-analysis.
An analysis that compared exercise to no treatment or a control intervention found a standardized mean difference between groups of -0.62 (95% CI: -0.81 -minus 0.42), indicating a moderate clinical effect with exercise.
A separate subanalysis of six well-designed trials (464 participants) that had adequate allocation concealment, intention-to-treat analysis and blinded outcomes resulted in a SMD of -0.18 (-0.47-0.11), which was not statistically signficant. An analysis of eight trials with long-term follow-up data (377 participants) indicated a small treatment effect with an SMD of -0.33 (95% CI: -0.63-minus 0.03).
In the final analyses of seven trials comparing exercise and psychological therapy that involved 189 participants, and four trials with 300 participants, there were no differences between groups (SMD -0.034, 95% CI -0.32-0.26; and SMD -0.11, 95% CI -0.34-0.12, respectively).
"The evidence about whether exercise for depression improves quality of life is inconclusive," the researchers wrote. "Further larger trials are needed to find out whether exercise is as effective as antidepressants or psychological treatments."
They also recommended future research focus on identifying specific types of exercise, as well as the number of sessions and duration needed to achieve the greatest clinical benefits.