Fighting depression: aerobic exercise is more effective than drugs

That is the startling and very welcome conclusion of a ground-breaking US study which compared the effects of exercise and antidepressants in adults suffering from major depressive disorder (MDD) over a period of 10 months.

Aerobic exercise has been prescribed for a wide range of medical disorders (including heart disease, arthritis and diabetes) and tipped as a potential treatment for various psychiatric conditions, especially depression. Population studies have shown an inverse relationship between physical activity and depression, and there is evidence that active people who become inactive are more at risk of depression that those who remain active.

The current study, by researchers from Duke University in North Carolina, was an extension of a previous trial in which 156 depressed adults aged 50 and over were randomly assigned to four months of exercise training (three supervised session per week, including 30 minutes of cycling, walking or jogging at 70-85% of heart rate reserve) or medication (with the antidepressant drug sertraline) or a combination of the two.

After four months, patients in all three groups showed significant and similar reductions in depressive symptoms: 60.4% of patients in the exercise group, 65.5% in the medication group and 68.8% in the combined group no longer met the criteria for major depressive disorder.

Questions remained, however, about the long-term impact of these interventions, and the current study was designed to follow up all the participants six months later to assess whether the benefits had persisted. At this stage exercise emerged as the clear winning therapy, with patients in the exercise group exhibiting significantly lower rates of depression (30%) than those in the medication and combined groups (52% and 55% respectively).

A more detailed analysis at 10 months of the 83 patients who had been assessed as being in remission after four months showed that those in the exercise group were more likely than those in either of the other groups to be considered either partially or fully recovered. Furthermore, only 8% of those in the exercise group had relapsed, compared with 38% in the medication group and 31% in the combination group.

During the six-month follow-up period the participants had been free to move between therapies, and it was interesting that just under half of those in the medication group took up exercise while around two thirds of those assigned to exercise in the original study remained active. As far as medication was concerned, 40% of those in the combination group took antidepressants during the follow-up period, compared with 26% in the medication group and 7% in the exercise group. Analysis taking account of these changes showed that patients who engaged in regular aerobic exercise during the six-month follow-up were less likely to be depressed at the end of that period, with each 50-minute increment in exercise per week associated with a 50% decrease in the odds of being classified as depressed.

‘Results of this relatively large, single-centre clinical trial indicate that exercise is a feasible therapy for patients suffering from MDD and may be at least as effective as standard pharma-cotherapy,’ report the researchers. It was not clear why people in the combined exercise-and-medication group fared worse than those assigned to exercise alone. But the researchers speculate that taking antidepressants might have compromised the psychological benefits (including feelings of personal mastery and enhanced self-esteem) that might be expected to come with following an exercise programme.

They stop short of claiming that exercise cures depression, because it is possible that those who continued to exercise during the follow-up period did so because they were already less depressed. More likely is ‘a potential reciprocal relationship between exercise and depression: feeling less depressed may make it more likely that patients will continue to exercise, and continuing to exercise may make it less likely that the patient will suffer a return of depressive symptoms.’

There were major limitations to the study, including self-selection of the participants – who might have been biased in favour of exercise – and self-reporting of exercise during the follow-up period, introducing possible inaccuracies into the data.

Nevertheless, conclude the researchers, ‘the present findings suggest that a modest exercise programme (eg three times per week with 30 minutes at 70% of maximum heart rate reserve each time) is an effective, robust treatment for patients with major depression who are positively inclined to participate in it, and that clinical benefits are particularly likely to endure among patients who adopt exercise as a regular, ongoing life activity.’

Psychosomatic Medicine 62:633-638 (2000)

Isabel Walker