Clinical Question: Is aerobic exercise effective in the treatment of mild to moderate depression?

Setting: Outpatient (specialty)

Study Design: Randomized controlled trial (single-blinded)

Allocation: Concealed

Synopsis: We know that exercise is an effective treatment for major depressive disorder. In this study, investigators randomly assigned 80 persons, 20 to 45 years of age with mild to moderate depression, to one of five exercise treatment groups: 7.0 kcal per kg per week (low dose) performed in three or five sessions per week; 17.5 kcal per kg per week (high dose) performed in three or five sessions per week; or flexibility exercise only (control) three days per week. The high dose is consistent with public health recommendations for physical activity. Outcomes were assessed by persons blinded to treatment group assignment.

Of the 80 randomized participants, 10 (12.5 percent) were lost to follow-up at 12 weeks. Using intention-to-treat analysis, patients assigned to either of the high-dose exercise groups were significantly more likely to have a clinically relevant response (defined as a 50 percent or more reduction in mean scores from baseline on the Hamilton Rating Scale for Depression) than patients in the control group (42 versus 23 percent; number needed to treat [NNT] = five).

No significant differences occurred between the two high-dose exercise groups. Patients in the low-dose exercise group who did three sessions per week also were more likely to have a significant response than patients in the control group (38 versus 23 percent; NNT = seven), but there was no significant difference between the low-dose group who did five sessions per week compared with the control group. The combined high-dose exercise group was not significantly more effective than the combined low-dose exercise group.

Bottom Line: High-dose and low-dose aerobic exercise are somewhat effective in the treatment of mild to moderate depression. Exercising three times per week is at least as effective as five times per week. To give a real world example of “high-dose” exercise, a man weighing 70 kg (154 lb) exercising to a heart rate of 145 beats per minute for 30 minutes on a treadmill expends approximately 350 kcal per session, requiring a total of three sessions per week. A previous study of walking or jogging at 70 to 80 percent of maximal aerobic intensity was also as effective as drug therapy in treating mild depression (Blumenthal JA, et al. Effects of exercise training on older patients with major depression. Arch Intern Med October 25, 1999;159:2349–56). (Level of Evidence: 1b)