Fight Depression with Exercise!

Summarized by Robert W. Griffith, MD
March 11, 2005

Introduction

It's well known that light therapy is helpful in treating depression, especially the seasonal type (seasonal affective disorder, or SAD), or the winter blues. Some depressed people may get their extra light by walking, biking, or running out-of-doors. A new study shows that, in fact, aerobic exercise itself has a beneficial effect on depression. It was reported in the American Journal of Preventive Medicine, and is summarized here.

What was done

Eighty volunteers aged between 20 and 45 were enrolled. They had mild or moderate depression, which was determined using the 17-item Hamilton Rating Scale for Depression (HAM-D).¹

The participants were randomly assigned to one of five treatment groups:

1. Low-dose aerobic exercise for 3 days a week
2. Low-dose aerobic exercise for 5 days a week
3. High-dose aerobic exercise for 3 days a week
4. High-dose aerobic exercise for 5 days a week
5. Control group - flexibility exercise for 3 days a week

Low-dose aerobic exercisers used a treadmill or stationary bicycle to achieve an energy expenditure of 7 kcal/kg/week, while high-dose exercisers expended 17.5 kcal/kg/week. In the control group, stretching-flexing exercises were done for 15-20 minutes per session.

HAM-D scoring was done once a week during the 12-week study. The effectiveness of aerobic exercise was based on the change in HAM-D score 12 weeks after starting the treatment.

What was found

The average age of the participants was 40. Three-quarters of them were women; their average BMI was 29.0 (an overweight, but not obese value). Nineteen of the 80 volunteers didn't complete the 12 weeks of the study, for various reasons.

The average HAM-D score was19.4 at the start of the study. There was considerable variability in the scores in the 5 different groups. The average reductions in HAM-D scores for the 3- and 5-day groups were about the same, in both the low- and high-exercise groups, respectively. For the final analysis, therefore, the results of both low-dose aerobic groups and both high-dose aerobic groups were compared with that of the control group.

The HAM-D scores were reduced by an average of 47% by high-dose aerobic exercise, 30% by low-dose aerobic exercise, and by 29% in the control group. The beneficial effect of high-dose aerobic exercise was statistically significant, when compared with the control group - that is to say, it could not have occurred by chance alone. Low-dose aerobic exercise, on the other hand, was no better than flexing and stretching.

Using a reduction in HAM-D score of 7 as a criterion for 'remission' (i.e. a temporary cure of the depression symptoms), the remission rate for high-dose aerobic exercise was 42%. (It was 26% for low-dose exercise, and 31% for the controls).

What do these findings mean?

In any evaluation of treatment for depression, attention must be given to the possibility of a large 'placebo effect'. The results in this study are comparable to those from studies of other forms of treatment. Remission rates for cognitive behavioral therapy (CBT) average 36% and for antidepressant drug therapy 42%. And the remission rates for the low-dose and control groups in this study are similar to those reported for placebo groups (dummy tablets) in drug studies.

How much exercise had to be done? The target - 17.5 kcal/kg/week - was based on recommendations established by public health authorities. The lack of difference between the 3-day and 5-day results shows that it's the amount of exercise done each week, rather than the frequency, that's important. As a very rough guide, 17.5 kcal/kg/week would be equivalent to using a treadmill to expend 175 calories every day if you weigh 70 kg (i.e.155 lbs); most good treadmills and stationary bikes give the number of calories expended.

For people with mild to moderate depression, aerobic exercise is clearly a beneficial form of treatment. It is best done in a gym, where you can have guidance from an expert and some encouragement from fellow exercisers. But check with your doctor first before starting an exercise program like this if you have any doubts about your health or, in any case, if you are over 55 or overweight.

Source

• Exercise treatment for depression: efficacy and dose response. AL. Dunn, MH. Trivedi, JB. Kampert,  et al., Am J Prev Med, 2005, vol. 28, pp. 1--8

Footnotes
1. Mild depression was defined as a score of 12 to 16 on the 17-item Hamilton Rating Scale for Depression, with moderate depression having a score of 17 to 25.

Related Links
Self-Help for Depression?
Treating Depression at Home
Aerobic Fitness May Preserve Mental Capabilities
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