Regular exercise can reduce depressive symptoms in adolescents

Physical activity may help alleviate depressive symptoms in adolescents, according to a systematic review and meta-analysis of clinical trials.

Participating in physical activity significantly helped reduce depressive symptoms, with a modest corrected effect size compared with controls (gram= -0.29, 95% CI -0.47 to -0.10, P=0.004), found Parco M. Siu, PhD, of the University of Hong Kong, and colleagues.

Across all the studies, the benefits of physical activity in reducing depressive symptoms resulted in a number needed to treat of six, the group reported in JAMA Pediatrics.

But it seemed that maintaining physical activity was necessary to reap these benefits. In the four studies that analyzed the results of follow-up an average of 21 weeks after the intervention, the significant differences in depressive symptoms disappeared (gram= -0.39, 95% CI -1.01 to 0.24, P=0.14). However, Siu’s group said this is “possibly due to the limited number of studies with follow-up results.”

In a secondary analysis, the researchers found certain factors that may predict exactly who would derive the greatest mental health benefits from physical activity. For example, adolescents 13 and older (vs. children under 13), those with a pre-existing mental illness (vs. those considered “well” or physically ill), and those with a diagnosis of depression viewed the larger effect sizes between physical activity and mental health.

The characteristics of the physical activity itself also seemed to matter. Participating in physical activity three times a week was associated with the greatest reduction in depressive symptoms, and the effect was greater when physical activity was unsupervised than when it was fully or partially supervised in the studies. In addition, studies in which the physical activity intervention lasted less than 12 weeks had a larger effect size.

Intensity level (low to moderate vs vigorous) and duration of the activity bout (less than 45 min vs 45 min or more) did not appear to play a role in the effect size of the result.

Siu’s group referred to a recent cross-sectional study who found a U-shaped association between physical activity and mental health, suggesting that 10 to 15 physical activity sessions per month were associated with the greatest mental health benefits.

“The identified individual-level moderators make statistical sense, as adolescents and youth with depression may have higher baseline depressive symptoms (more room for improvement in the dependent variable) and lower levels of physical activity (more room for improvement in the independent variable). pointed a accompanying editorial by Eduardo E. Bustamante, PhD, of the University of Illinois Chicago, and colleagues.

“The finding that results were less substantial when interventions were too frequent (or not frequent enough) and lasted too long (or not long enough) may reflect that part of the association of physical activity with depression reduction is the sense of accomplishment associated with successful completion, a role that requires achievable but challenging goals,” they added.

A wide range of physical activity programs were evaluated in the studies included in the meta-analysis, from dance, swimming, sports, running, treadmills, ellipticals, exercise games, and more. However, the common thread was an emphasis on aerobic exercise.

In the 21 included studies, the average age of the participants was 14 years and 47% of them were children. Most of the included studies (17 of 21) were randomized controlled trials and the remainder were non-randomised controlled trials.

“The evidence that physical activity is effective medicine for mental health is strong; now we must find ways to get people to take it,” Bustamante’s group concluded.