Why Does Outdoor Exercise Combat Depression?

Why Does Outdoor Exercise Combat Depression?

Research has demonstrated that combining light therapy with physical activity can be effective in treating depression, particularly seasonal affective disorder or winter depression. For some adolescents with depression, engaging in aerobic activities like walking, cycling, or outdoor running can provide exposure to ample natural light. In fact, the ability of outdoor activities in bright sunlight to counteract depression stems from the dual effects of combining light therapy with aerobic exercise.

How should one exercise? An 80-participant study examined individuals with mild to moderate depression, diagnosed using the 17-item Hamilton Depression Rating Scale. The participants were randomly divided into five treatment groups: ① Low-intensity aerobic exercise for 3 days a week; ② Low-intensity aerobic exercise for 5 days a week; ③ High-intensity aerobic exercise for 3 days a week; ④ High-intensity aerobic exercise for 5 days a week; ⑤ Control group performing stretching exercises for 3 days a week.

Low-intensity aerobic exercise resulted in an energy expenditure of 7 kcal/kg per week, while the high-intensity exercise group expended 17.5 kcal/kg per week. The control group engaged in stretching exercises for 15-20 minutes each time.

During the 12-week study period, weekly evaluations using the Hamilton Depression Rating Scale were conducted. The effectiveness of aerobic exercise was determined based on the change in Hamilton Depression Rating Scale scores within the 12 weeks of initiating exercise therapy. The results indicated that both the high-intensity and low-intensity exercise groups, whether exercising for 3 or 5 days, exhibited similar decreases in average Hamilton Depression Rating Scale scores. Consequently, a comparison was made between the low-intensity and high-intensity aerobic exercise groups and the control group to draw a definitive conclusion. Ultimately, the average Hamilton Depression Rating Scale score decreased by 47% in the high-intensity aerobic exercise group, 30% in the low-intensity aerobic exercise group, and 29% in the control group (performing stretching exercises). This trial's insight suggests that exercise intensity is more important than frequency, with higher-intensity aerobic exercise improving the cognitive behavior of individuals with depression. According to recommendations from exercise medicine experts, the target for energy expenditure through exercise is 17.5 kcal/kg per week, with exercise occurring 3-5 days per week. For patients with mild to moderate depression, aerobic exercise evidently proves to be an effective therapeutic approach.