Sources of evidence	Findings
Meta-analysis of 14 RCTs on exercise compared with no treatment or cognitive therapy1	Exercise produced large, clinically significant reductions in depression symptoms, comparable with cognitive therapy effects; methodologic weaknesses in RCTs limited recommendations
Cochrane meta-analysis of 25 RCTs2 (updates earlier study1)	Exercise produced large, clinically significant reductions in depression symptoms, but only moderate improvement shown when analysis limited to three highly rigorous trials; exercise effects comparable with those of cognitive therapy
Meta-analysis of 11 RCTs from peer-reviewed journals3	Quantitative analysis of exercise monotherapeutic effects showed large effect size; qualitative review of four RCTs on exercise as adjunct treatment also positive; methodologic weaknesses in RCTs are common
Nonsystematic review of multiple meta-analyses4	The consistent tendency for meaningful exercise-induced reductions of depression symptoms were noted, as well as common methodologic problems (e.g., no intention-to-treat analysis, poor allocation concealment, non-blinded assessment); recommendation to use exercise
Systematic review of five RCTs comparing exercise with non-active control for older patients with depression5	Each RCT on older adults (i.e., 50 to 84 years of age) with depression showed greater symptom reduction from exercise than from non-active control conditions (e.g., student visits); methodologic weaknesses noted
RCT (n = 80) comparing aerobic with anaerobic exercise in adults with depression8	Adults with mild to moderate depression were assigned to high-energy aerobic exercises, low-energy aerobic exercises, or a low-energy stretching control condition; higher energy expenditure produced greater reductions in depression symptoms; low-energy aerobic exercise had same effect as control
Small RCT comparing effects of exercise frequency and group versus individual effects9; another RCT comparing supervised exercise with home exercise10	High-frequency (i.e., three to five times weekly) aerobic activity produced greater symptom reduction compared with low-frequency (i.e., once weekly) aerobic activity; no differences in symptom reduction between exercises performed in groups versus individually, or between supervised exercise versus home exercise
Cochrane meta-analysis of 16 RCTs with participants younger than 20 years11	Most studies were conducted in the general population and not clinically diagnosed groups; in the few studies on children in clinical treatment, no statistically significant differences were seen among treatment with exercise, low-intensity relaxation, psychosocial intervention, or no intervention