Exercise may have an effect on mood by releasing the body’s own painkilling and euphoria-producing chemicals (endorphins) and other neurotransmitters that send electrical and chemical signals to the brain, affecting sleep, appetite, alertness, and level of energy. Often exercise is done in groups or with a trainer, and the social contact may be a critical element for improving mood. If exercise is done outdoors, or away from the person’s home, the very act of getting out and doing something positive may be therapeutic. Exercise can also act as a diversion for negative thinking and helps to take the patient out of the hopeless, withdrawn, “dark” state of mind.
What Is the Evidence?
A meta-analysis of eighty studies (regardless of their methodological quality) revealed that exercise decreased depression scores significantly when compared to controls who did not exercise. The antidepressant effect occurred with all types of regular exercise, independent of sex or age, and overall mood increased with the duration of therapy.2 A Cochrane review of thirty-seven trials compared exercise to no treatment or another form of treatment. The authors concluded that exercise is moderately more effective than a control intervention for reducing symptoms of depression. When they analyzed the trials, those studies that were of the highest quality showed that the impact of exercise was less on relieving the symptoms of depression. Exercise was no more effective than psychological or pharmacological therapies for depression.3 Another meta-analysis looked at seventy-two potentially relevant studies. Of these, only fourteen studies fulfilled the inclusion criteria for their analysis. Unfortunately, the fourteen studies had important methodological weaknesses: Only three trials adequately concealed randomization to groups; intention-to-treat analysis (where none of the patients are excluded and all patients are analyzed according to randomization) was undertaken in only two of the trials; and assessment of outcome was blinded in only one. Results: When the exercise treatment groups were compared with no treatment, exercise significantly reduced symptoms of depression. The size of the effect was significantly greater in trials that had shorter follow-up times. The authors concluded, however, that they could not determine from these poorly designed trials the effectiveness of exercise in reducing symptoms of depression. They stated that there was a lack of good-quality research available with data gathered from clinical populations that included adequate patient follow-up. Martinsen and Stephens identified eight experimental exercise-intervention trials in clinically depressed patients. They found that exercise was associated with reductions in depression scores in all of the studies. One hundred fifty-six adult volunteers with major depressive disorder were randomly assigned to one of three groups: aerobic exercise, sertraline therapy (a SSRI antidepressant prescription drug), or a combination of exercise and sertraline over a four-month period. At the completion of the four months, patients in all three groups exhibited significant improvement; the proportion of participants whose depression went into remission was comparable across the three treatment conditions. After ten months, however, remitted subjects in the exercise group had significantly lower depression relapse rates than subjects in the medication group. Exercising on one’s own during the follow-up period was associated with a reduced probability of depression diagnosis at the end of that period. These findings suggest that perhaps in the long term, exercise as a therapy may have a better chance of reducing or eliminating depression symptoms, and the people who motivate themselves to continue with an exercise practice are more likely to get respite from depressive symptoms.6 It is often difficult to treat elderly patients who are depressed. Regular physical exercise in the elderly is associated with decreased depressive scores. In one study those moderately depressed elderly subjects who were randomly allocated to walking exercises showed a significant decrease in depression compared to controls at six weeks.