A meta-analysis was conducted to examine the effects of exercise on anxiety. Because previous meta-analyses in the area included studies of varying quality, only randomized, controlled trials were included in the present analysis. Results from 49 studies show an overall effect size of -0.48, indicating larger reductions in anxiety among exercise groups than no-treatment control groups. Exercise groups also showed greater reductions in anxiety compared with groups that received other forms of anxiety-reducing treatment (effect size = -0.19). Because only randomized, controlled trials were examined, these results provide Level 1, Grade A evidence for using exercise in the treatment of anxiety. In addition, exercise dose data were calculated to examine the relationship between dose of exercise and the corresponding magnitude of effect size.
Several meta-analyses examining the effects of exercise on depression have been criticized for including studies of poor methodological integrity. More recent meta-analyses addressed the most common criticism by including only randomized control trials; however, these analyses suffer from incomplete literature searches and lack of moderating variable analyses. Using a more extensive search procedure, the current meta-analysis examines the effects of exercise on depressive symptoms in 58 randomized trials (n = 2982). An overall effect size of -0.80 indicates participants in the exercise treatment had significantly lower depression scores than those receiving the control treatment. This frac34; SD advantage represents level 1, Grade A evidence for the effects of exercise upon depression. Analysis of moderating variables examined the influence of population characteristics, exercise characteristics and methodological characteristics. Examination of clinical significance in 16 trials with clinically depressed patients found 9 of 16 exercise treatment groups were classified as 'recovered' at post-treatment, with another three groups classified as 'improved'. Analysis showed dropout rates for the exercise treatment were similar to those found in psychotherapeutic and drug interventions.
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