Intervening with physical activity appears to mitigate depressive symptoms in children and adolescents, a systematic review and meta-analysis of almost 2,500 participants found. Greater reductions were observed for children older than 13 years and those having a diagnosis of mental illness and/or depression versus other conditions, according to Hong Kong researchers reporting in.
“There is an urgent need to explore novel treatment approaches that can be safely, feasibly, and widely implemented in the daily routine of depressed children and adolescents,” said study coauthor Parco M. Siu, PhD, exercise physiologist and associate professor in the school of public health at the University of Hong Kong, in an interview. “Given the observed association with significant reductions in symptoms, clinical practice guidelines should consider the role of physical activity for improving the mental health of young populations.”
Dr. Siu further noted that while current guidelines suggest psychotherapy and/or pharmacotherapy for children with this common mood disorder, adherence to these can be problematic, and surveys show that nearly 80% do not receive appropriate disorder-specific medical care.
Dr. Siu’s team drew on 21 international studies, including 17 randomized controlled trials, published from 1987 to 2021 and comprising 2,444 young participants, mean age 14, 53% girls. Eligible studies compared the effect of exercise on depression versus a control condition.
In 12 studies, participants had a somatic or psychiatric disorder such as obesity, diabetes, depression, and attention-deficit/hyperactivity disorder. The mean duration of the prescribed physical activity program was 22 weeks (6-144 weeks), while the frequency of weekly sessions ranged from 2 to 5 days, with 3 days per week most common and mean duration of 50 minutes (30-120 minutes). Regimens ranged from aerobic exercise on fitness equipment such as treadmills, stationary bikes, and ellipticals, to running, swimming, dancing, sports, and exercise games.
In meta-analysis of postintervention differences, physical activity was associated with a significant reduction in the pooled estimate of depressive symptoms compared with the control condition (Hedges g statistic [effect size] = −0.29; 95% confidence interval, −0.47 to −0.10; P = .004). This was driven by moderate to large effect sizes in adolescents (g = −0.44) and children with diagnosed depression (g = −0.75).The differences, however, were not detectable after a mean follow-up of 21 weeks, possibly owing to the limited number of studies with follow-up outcomes, the authors conceded.
Despite the strong association, the mechanisms underlying the antidepressant properties of physical activity remain uncertain. “Potential pathways include the activation of the endocannabinoid system to stimulate the release of endorphins, an increase in the bioavailability of brain neurotransmitters such as serotonin, dopamine, and noradrenaline, which are reduced in depression, as well as long-term changes in brain plasticity,” Dr. Siu said.
In addition, psychosocial and behavioral hypotheses suggest that physical activity can lead to improvements in self-perception, social interactions, and self-confidence. However, he added, depressive phenomenology is multifaceted and individual, so isolating the effects that physical activity have on specific symptoms may not be possible.
Physical activity appears to enhance the treatment of cognitive and affective symptoms in depression, Dr. Siu continued, and a combination of physical activity and pharmacotherapy may also reduce relapse risk, improve adherence to antidepressants, and promote better management of adverse effects, compared with pharmacotherapy alone. “More research is warranted to explain if and how these mechanisms moderate the effect of physical activity, and whether these changes are also present in younger populations,” he said.
Still unanswered is the question of how vigorous activity has to be in order to have an effect, Dr. Siu said. “Future studies should investigate the influence of parameters such as frequency, duration, and supervision of exercise sessions to determine the optimal dose and mode of delivery of the intervention for depressive symptom management.”
But would group activity likely have broader benefits than solitary exercise? “It is still unclear whether there’s a difference between the effect of solitary activities and team sports,” Dr. Siu said.
In an accompanyingon the meta-analysis, Eduardo E. Bustamante, PhD, an exercise psychologist in the department of kinesiology and nutrition at the University of Illinois at Chicago, and colleagues called the meta-analysis “part of a potential watershed moment” in the field of exercise as therapy for psychological disorders. “The work is timely, aligning with the rise of mental health disorders in adolescents, and the methods are rigorous (e.g., random-effects models, risk-of-bias assessment, sensitivity analyses).”
Dr. Bustamante said the literature on physical activity in children has lagged behind that for adults, so this meta-analysis provides a welcome “critical mass” of evidence of benefit in children, in an interview. “Though the benefit is relatively small, it’s exciting to see the results come in positive specifically to depression.” In his view, the effect of exercise is likely to be less pronounced in children than in adults, especially older ones, as they have fewer inflammatory and other systemic health problems that might improve with exercise. “And we tend to see bigger effects in children with a diagnosis like ADHD or clinical depression.”
But the bottom line is clear: “The evidence that physical activity is effective medicine for mental health is robust; now we need to find ways to get people to take it.”
This work was supported by the Health and Medical Research Fund of the Food and Health Bureau, Hong Kong Special Administrative Region Government, and the Seed Fund for Basic Research of the University of Hong Kong. The authors and editorial commentators disclosed no conflicts of interest.