Exercising as little as three hours a week can have a profound effect on the symptoms of depression. Researchers are puzzled about the exact reason for the benefits, but studies conducted with animals suggest that exercise increases serotonin, dopamine and norepinephrine levels. Exercise also releases endorphins, chemicals naturally produced in the body, which reduce the experience of pain and enhance a sense of well-being.
Numerous studies in human beings have shown that a variety of exercises, such as weight training and aerobic exercise (exercise where you breathe hard and your heart beats faster) can improve mood. This effect is especially noticeable in older adults, but works with other age groups as well. In some studies, regular and sustained exercise was found to be as effective as (and sometimes more effective than) psychotherapy and standard medications for treating certain individuals with symptoms of depression.
Consult with your health care provider before starting an exercise program. Your program should incorporate both strength training (such as lifting weights) and cardiovascular training (anything where your heart rate increases for an extended period). Always start slow and progress gradually. Most health practitioners suggest that exercising 20-30 minutes a day, three times a week, is a good place to start. Gradually move up to the point where you can exercise for a full hour, three times a week, or 30 minutes six times a week. The goal is at least 3 total hours of exercise each week.