A number of studies, dating from the mid 1990s to more recently, show that cardio vascular and resistance or weight training combat mild to severe depression. It turns out that exercise results in a surge of serotonin, the neurotransmitter which make us feel good right after working out, as well as a long-term mood shift once you've started exercising regularly. These effects may be related in part to an increased growth in brain cells. Regular exercise has favorable effects on the immune system as well, which may promote health, especially in stressed and/or depressed individuals.
A study of 12,028 randomly selected individuals age 20-79 showed that increasing physical activity was associated with a 70% reduction in self-reported stress as well as decreased life dissatisfaction. Even 2-4 hours of walking per week was associated with significant gains. Another study of a group of employees showed reductions in stress levels and depression, and improvements in feelings of health and vitality, after a 24 week program of aerobic exercise compared to a control group. A 1985 study looked at 43 patients with depression; about half were treated for the condition with antidepressants. Patients were randomized to receive 9 weeks of exercise training (aerobic for one hour, three times a week at 50-70% maximum aerobic capacity) or occupational therapy. Exercise was associated with statistically significantly greater decreases in depression as measured by the Beck Depression Inventory (a measure of symptoms of depression). In another study 86 patients with depression who were treated with antidepressants but did not have a therapeutic response were randomized to exercise or health education classes. Exercise involved weight bearing exercise for 45 minutes twice a week for ten weeks. More patients treated with exercise had an improvement as measured by a 30% improvement on a scale for the measurement of depression called the Hamilton Depression Scale (55% got better with exercise versus 33% without, a difference that was statistically significant). In another study 83 patients with major depression underwent aerobic exercise training versus not changing what they were doing before. Exercise training was associated with better symptom improvement in terms of anxiety and general symptoms but not depression.
Other studies have shown the impressive results of exercise in fighting or reducing symptoms of depression. For example, researchers at Freie University in Berlin also found that thirty minutes of exercise a day significantly improved the moods of patients who had been suffering from depression for nine months. In a report published in the British Journal of Sports Medicine, 12 patients with depression underwent 10 weeks of training on a treadmill at 30 minutes a day. There was a statistically significant 6-point drop in depressive symptoms as measured with the Hamilton Depression Sale. The authors concluded, and I agree, that exercise could be at least as effective as drugs in treating mild to moderate depression.
One study looked at 156 patients with major depression over age 50 who were randomly assigned to aerobic exercise, antidepressants (sertraline) or a combination of the two for 16 weeks. All patients showed an improvement in symptoms of depression with an essentially identical response between the groups (1).
A recent report in 2005, explained the results of a 3-year long study in 80 patients designed to test whether exercise is an efficacious treatment for mild to moderate major depressive disorder and what amount would be needed to see a positive difference in depressed people. The report, published in The Journal of Preventive Medicine (January 2005) found that a half-hour a day of exercise six days a week is the ideal "dosage" to improve the mood of people who have mild to severe depression. Researchers compared two groups of depressed patients and found that while the group that performed 80 minutes of exercise a week received little to no mental-health benefit (30% reduction with 29% in a "placebo exercise" group), the three-hour-a-week group had a substantial (47%) reduction in symptoms.
Exercise may also complement the effects of antidepressant medication in depressed patients. One study added exercise to antidepressant treatment in 17 patients who did not have a complete response to antidepressant medication. Exercise was prescribed using currently recommended public health guidelines - at least 30 minutes of aerobic activity a day - with both supervised and home based sessions. There was a 10-point decrease in the Hamilton Depression Scale (a clinically significant change) in the eight patients who completed the study.
Exercise is far less expensive, and more easily accessible, than medication and psychotherapy. Plus it has none of the side effects, such as sexual dysfunction as seen with some antidepressants. Indeed, the "side effects" of using exercise as your antidepressant are beneficial to your general well being: improved cardiovascular health, increased strength, and weight loss.
1. Blumenthal, J.A., Bayak, M.A., Moore, K.A. Effects of exercise training on older patients with major depression. Archives of Internal Medicine. 1999;159:2349-2356.