A study of exercise in a supervised laboratory setting demonstrated this relationship in 80 adults age 20 to 45 with mild-to-moderate depressive symptoms. Subjects were randomly assigned to an exercise control group (3 days/week of flexibility exercise) or 1 of 4 aerobic exercise groups that varied in total energy expenditure (a “low dose” of 7.0 kcal/kg/week or a “public health dose” of 17.5 kcal/kg/week). The 17-item Hamilton Rating Scale for Depression (HRSD) was the primary outcome measure.
After 12 weeks, HRSD scores declined from baseline by 47% in subjects engaged in the public health dose of aerobic exercise—a significant reduction. Depressive symptoms declined by 30% in the low-dose exercisers, but this was comparable to the 29% reduction in the control group.
Comment. The effective exercise dose in this study is similar to the public health recommendation of 30 minutes of moderate-to-vigorous activity on all or most days per week (see Related Resources). Antidepressant effects have been associated with more modest physical activity, however, which may be easier to initiate and maintain for individuals with depression. The study did not find significant differences in outcomes based on the subjects’ age, gender, or exercise frequency. Nevertheless, the exercise dose may be important to produce an antidepressant effect.
An inverse relationship? Compared with occasional exercise, habitual physical activity usually is associated with greater cardiorespiratory fitness. Whether habitual activity also results in fewer depressive symptoms and greater emotional well-being remains to be seen.
A large, cross-sectional, National Institutes of Health-funded study of 5,451 men and 1,277 women12 suggests an inverse relationship between physical activity and depressive symptoms. Subjects underwent a treadmill exercise test to evaluate physical fitness. A 20-point self-report scale assessed depressive symptoms, and the General Well-Being Schedule13 was used to assess emotional well-being. Depressive symptoms were more severe in “inactive” and “insufficiently active” subjects compared with “sufficiently active” and “highly active” subjects.
On the other hand, although regular exercise may be associated with reduced depressive symptoms in the population at large, no cause-effect relationship was found in a population-based, longitudinal study of 5,952 twins.14
A prospective, randomized, controlled trial15 suggests that exercise could be an important treatment tool in patients diagnosed with MDD. The 202 adult subjects (153 women, 49 men) were randomly assigned to 1 of 4 treatments:
- supervised exercise in a group setting
- home-based exercise
- antidepressant medication (sertraline, 50 to 200 mg/d)
- placebo pills.
Patients underwent the structured clinical interview for depression and completed the HRSD. After 16 weeks, 41% of participants achieved remission, defined as no longer meeting MDD criteria and a HRSD score <8. Compared with placebo controls, patients receiving active treatments tended to have higher remission rates:
- 45% with supervised exercise
- 40% with home-based exercise
- 47% with medication
- 31% with placebo.
Comment. The placebo response rate was relatively high in this study, and antidepressant dosages might not have been optimal. These factors could explain why remission rates with supervised exercise and antidepressant medication were comparable. The study might have been more reliable if it had included a medication plus exercise arm. Patients treated in an office setting might not fare as well as these study subjects whose exercise was supervised.
Postpartum depression occurs in an estimated 13% of new mothers.16 In a controlled trial, 80 women with depression at 4 weeks postpartum were assigned to either:
- an exercise support program (1 hour supervised exercise and 2 sessions at home each week for 3 months)
- standard care.
Prescribing exercise regimens for depressed patients
Most depressed patients can benefit from aerobic exercise or high-intensity progressive resistance training (PRT). Consult with your patient’s primary care physician before designing an exercise regimen. Incorporate warm-up and cool-down periods during each exercise session.
Aerobics. A 30- to 45-minute daily regimen of running, walking, swimming, biking, dancing, or elliptical training is recommended for most people. An optimum regimen achieves a target heart rate of 70% to 85% of the individual’s maximum heart rate. A goal of 40% to 50% of maximum heart rate is an appropriate goal for patients starting an exercise program. At least 10 minutes of aerobic activity is necessary to produce the desired benefit.
PRT. High-intensity progressive resistance training may be recommended in consultation with a physical therapist or certified trainer. This usually consists of 30 to 45 minutes of systematic training of various muscle groups 3 days a week. An optimal resistance of 80% of maximal load is desirable, but this may be adjusted for individual patients. Lifting weights, push-ups, sit-ups, using resistance bands, and heavy gardening may be part of this regimen.