Physical Activity Interventions to Alleviate Depressive Symptoms in Children and Adolescents

A Systematic Review and Meta-analysis

Francesco Recchia, MSc¹; Joshua D. K. Bernal, BSc¹; Daniel Y. Fong, PhD²; et alStephen H. S. Wong, PhD³; Pak-Kwong Chung, DPE⁴; Derwin K. C. Chan, PhD⁵; Catherine M. Capio, PhD⁵; Clare C. W. Yu, PhD⁶; Sam W. S. Wong, DPT⁷; Cindy H. P. Sit, PhD³; Ya-Jun Chen, PhD⁸; Walter R. Thompson, PhD⁹; Parco M. Siu, PhD¹

Author Affiliations Article Information

JAMA Pediatr. 2023;177(2):132-140. doi:10.1001/jamapediatrics.2022.5090

Key Points

Question  Can physical activity interventions alleviate depressive symptoms in children and adolescents?

Findings  This systematic review and meta-analysis included 21 studies involving 2441 participants. The results indicate that physical activity interventions were associated with significant reductions in depressive symptoms compared with the control condition.

Meaning  The available evidence supports physical activity interventions as an alternative or adjunctive approach to alleviate depressive symptoms in children and adolescents, substantiating the beneficial influence of physical activity on the mental health of pediatric populations.

Abstract

Importance  Depression is the second most prevalent mental disorder among children and adolescents, yet only a small proportion seek or receive disorder-specific treatment. Physical activity interventions hold promise as an alternative or adjunctive approach to clinical treatment for depression.

Objective  To determine the association of physical activity interventions with depressive symptoms in children and adolescents.

Data Sources  PubMed, CINAHL, PsycINFO, EMBASE, and SPORTDiscus were searched from inception to February 2022 for relevant studies written in English, Chinese, or Italian.

Study Selection  Two independent researchers selected studies that assessed the effects of physical activity interventions on depressive symptoms in children and adolescents compared with a control condition.

Data Extraction and Synthesis  A random-effects meta-analysis using Hedges g was performed. Heterogeneity, risk of bias, and publication bias were assessed independently by multiple reviewers. Meta-regressions and sensitivity analyses were conducted to substantiate the overall results. The study followed the PRISMA reporting guideline.

Main Outcomes and Measures  The main outcome was depressive symptoms as measured by validated depression scales at postintervention and follow-up.

Results  Twenty-one studies involving 2441 participants (1148 [47.0%] boys; 1293 [53.0%] girls; mean [SD] age, 14 [3] years) were included. Meta-analysis of the postintervention differences revealed that physical activity interventions were associated with a reduction in depressive symptoms compared with the control condition (g = −0.29; 95% CI, −0.47 to −0.10; P = .004). Analysis of the follow-up outcomes in 4 studies revealed no differences between the physical activity and control groups (g = −0.39; 95% CI, −1.01 to 0.24; P = .14). Moderate study heterogeneity was detected (Q = 53.92; df = 20; P < .001; I² = 62.9% [95% CI, 40.7%-76.8%]). The primary moderator analysis accounting for total physical activity volume, study design, participant health status, and allocation and/or assessment concealment did not moderate the main treatment effect. Secondary analyses demonstrated that intervention (ie, <12 weeks in duration, 3 times per week, unsupervised) and participant characteristics (ie, aged ≥13 years, with a mental illness and/or depression diagnosis) may influence the overall treatment effect.

Conclusions and Relevance  Physical activity interventions may be used to reduce depressive symptoms in children and adolescents. Greater reductions in depressive symptoms were derived from participants older than 13 years and with a mental illness and/or depression diagnosis. The association with physical activity parameters such as frequency, duration, and supervision of the sessions remains unclear and needs further investigation.

Introduction

Depression is the second most prevalent mental disorder among children and adolescents, with an estimated prevalence rate of 6.2% globally.¹ Early childhood depression is associated with severe adverse outcomes, including difficulties with social functioning, poor mental and physical health, and suicide.^2,3 The incidence of depressive symptoms at a young age is a strong predictor of future mental disorders, as it has been shown that up to 67% of youth with depressive symptoms are at risk of developing full-syndrome depressive or anxiety disorders in adulthood.^4–6

The available clinical practice guidelines suggest the use of psychotherapy and/or pharmacotherapy to alleviate depressive symptoms in children and adolescents.^7–9 However, both approaches have limitations that can reduce treatment adherence. Lack of time, fear of stigmatization, parental mistrust of the therapist, and no perceived need for treatment can be strong barriers to childhood psychotherapy,¹⁰ whereas adverse effects, including sleep disturbances, gastrointestinal distress, and even suicide, have been associated with antidepressant use in pediatric patients.¹¹ Data from a national survey in the US indicated that only 34% of community-dwelling children and adolescents seek and receive disorder-specific treatment or help from the mental health sector.¹² Data from previous surveys are even more alarming, as they showed that nearly 80% of children and adolescents needing mental health treatment did not receive appropriate medical care.¹³ There is an urgent need to explore novel treatment approaches that can be safely, feasibly, and widely implemented in the daily routine of children and adolescents with depression. Physical activity interventions are potential complementary or alternative treatments for depression in youth, as they have been shown to alleviate depressive symptoms in adults^14,15 and have been endorsed by international guidelines (eg, European Psychological Association, the UK National Institute of Health and Care Excellence, Canadian Network for Mood and Anxiety Treatments) as an official treatment for adult depression.^16–18 Furthermore, physical activity is generally safer and more accessible than other clinical depression treatments.

Previous meta-analyses have attempted to synthesize the potential benefits of physical activity on depressive symptoms in younger cohorts,^19–22 but several limitations undermine the interpretation of the findings. Three of these reviews excluded studies of participants with somatic or psychiatric comorbidities, which can seriously challenge the generalizability of the results to everyday settings.^20–22 Children and adolescents with depression are at high risk of developing comorbidities, as research has shown that up to 75% of children with depression reported a comorbid anxiety disorder and up to 57% developed attention-deficit disorder.^23,24 In addition, all reviews based their results on generally small sample sizes, with the largest review including 15 studies in its analysis.²⁰

With this systematic review and meta-analysis, we aimed to gather a wider range of studies to provide critical insight into the association between physical activity interventions and depressive symptoms in children and adolescents. Furthermore, we aimed to identify possible participant- and trial-related characteristics that might moderate the overall treatment effect.

Methods

This meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered at the International Prospective Register of Systematic Reviews (CRD42021287944).

Search Strategy and Selection Criteria

We searched PubMed, CINAHL, PsycINFO, EMBASE, and SPORTDiscus from inception to February 2022 for relevant articles written in English, Chinese, or Italian. The search terms used are available in eAppendix 1 in the Supplement. References of previous meta-analyses were also examined. Two authors (F.R. and J.D.K.B.) independently scrutinized each study using preestablished criteria. Any disagreement on the inclusion of a study was arbitrated by a third author (P.M.S.) and resolved by consensus.

We included published randomized clinical trials (RCTs) and studies with a quasi-experimental design (nonrandomized clinical trials [NRCTs]) investigating the effects of an aerobic-type physical activity intervention on depressive symptoms in children and adolescents (aged <19 years). Aerobic-type physical activity was defined using World Health Organization guidelines as “an activity in which the body’s large muscle groups move in a rhythmic manner for a sustained period of time.”^25(p1452) The intervention could be conducted in a laboratory setting or integrated as part of a school curriculum and could be implemented as monotherapy or added to the current physical education routine, as an education component, or to treatment as usual. We included studies that implemented a control condition in the form of no treatment, waiting list, education/attention control, or treatment as usual. Only studies with an intervention that was at least 4 weeks long were included. To increase the generalizability of the results, studies with participants with somatic or psychiatric disorders were also included.

Main Outcome

The primary outcome was depressive symptoms as assessed using a validated depression rating scale at the end of the intervention period and at the last available follow-up. For studies using multiple scales, observer-rated scales were preferred over self-reported scales. If more than 1 depression scale was reported, we chose the most commonly used scale to reduce heterogeneity.

Data Extraction

Two investigators (F.R. and J.D.K.B.) independently extracted relevant data from the selected studies using preestablished criteria. For each study, sample size, depressive symptoms mean scores, and SDs were extracted to calculate the effect size. When relevant data were not clearly reported, we contacted the authors. When authors were unresponsive or unreachable, we used previously validated methods to extract means and SD; namely, data were computed from the P values or CIs provided in the study or from the included graphs.²⁶ Data from multiarm trials were combined and added as a single comparison group.²⁶ Inconsistencies in the data extraction between the 2 investigators were resolved by consensus after consulting with a third investigator (P.M.S.).

Additional information regarding participant and trial characteristics was collected to determine their association with physical activity interventions and depressive symptoms. These characteristics included participants’ age, sex, and health status; intervention frequency, intensity, duration, and overall volume; type of control; whether the intervention was supervised and used as monotherapy or as an integrated part of an education program; and whether intention-to-treat outcomes were available. Data on race and ethnicity were not collected as they were not within the objectives of this study.

Risk-of-Bias Assessment

Risk of bias was assessed using the Cochrane risk-of-bias tool for randomized trials.²⁷ Two investigators (F.R. and J.D.K.B.) independently assessed each study as having low risk of bias, some concerns, or high risk of bias. Any discrepancies between the 2 evaluations were resolved by consensus after consulting a third investigator (P.M.S.). The criteria used for the risk-of-bias assessment are available in eAppendix 2 in the Supplement.

Data Analysis

The meta-analysis was performed using R, version 4.2.0 (R Foundation for Statistical Computing). To account for variations in the included studies regarding participants and instruments used to assess depressive symptoms, a random-effects model (Hartung-Knapp method) was used to calculate pooled estimates (Hedges g) and the 95% CI. Hedges g was calculated from the postintervention or follow-up means, SDs, and sample sizes for each comparison of interest. A negative effect size indicates a beneficial effect of the physical activity intervention compared with the control condition. Cochran Q test was used to assess between-study heterogeneity. Higgins I² statistic was used to define the percentage of variability that was due to between-study heterogeneity rather than sampling error. The I² values of 25%, 50%, and 75% were taken to represent low, moderate, and high levels of heterogeneity, respectively.²⁸

The overall effect of the physical activity interventions on reducing depressive symptoms was used to calculate the number needed to treat.²⁹ Publication bias was assessed by a visual examination of the funnel plot symmetry and by Egger regression test, for which P < .10 indicates significant publication bias.³⁰ Sensitivity analyses were conducted by recalculating the effect size after excluding potential outliers. We defined outliers as studies with an effect size where the 95% CI did not overlap with the 95% CI of the aggregated effect size.³¹

Meta-regressions were performed to assess the influence of potential moderators on the overall effect size to explain any possible heterogeneity. Four primary moderators were chosen a priori: total physical activity volume, participants’ health status, whether the allocation and/or assessments were concealed, and whether the study was an RCT or NRCT. We chose these moderators based on their possible associations with physical activity, depressive symptoms, or both and because previous meta-analyses on exercise for depressive symptoms in adults showed significant associations with similar moderators.^32,33 Multiple linear regression analyses using a mixed-effects model with maximum likelihood estimation were performed using the 4 primary moderators.³⁴ Univariable analyses were performed to explore whether the potential participant and trial characteristics moderated the overall effect. The threshold for significance was a 2-sided P < .05. Definitions of all moderators and the codes used for each level are included in eTable 1 in the Supplement.

Results

The database search identified 9153 unique records. After assessment of titles and abstracts, 104 full texts were screened, and 21 studies involving 2441 participants were included in the meta-analysis.^35–55 A visual description of the search results is available in the PRISMA flowchart in eFigure 1 in the Supplement.

Study Characteristics

A summary of the characteristics of the included studies is presented in Table 1. Of the 21 studies included, 17 were RCTs,^{36–41,43–49,51,52,54,55} and 4 were NRCTs,^35,42,50,53 and included 2441 participants (1148 [47.0%] boys; 1293 [53.0%] girls). The mean (SD) age of participants at baseline was 14 (3) years. Eighteen studies^{35–40,42–46,48,49,51–55} included both boys and girls, and 3 studies^41,47,50 included female participants only.

Twelve studies included participants with a somatic or psychiatric disorder, such as depression, obesity, attention deficit hyperactivity disorder, and diabetes.^{36–38,40,46,49–51,53–55} The mean duration of the prescribed physical activity program was 22 weeks (range, 6-144 weeks). The frequency of the physical activity sessions ranged from 2 to 5 days per week, with 3 days per week being the most commonly used frequency (8 studies^{35,36,38,40,47,48,50,55}). The mean duration of the physical activity sessions was 50 minutes (range, 30-120 minutes). Most interventions were fully supervised (16 studies^{35–37,39,41–43,45,47–49,51–55}), and 2 did not report any supervision.^40,50 Physical activity was prescribed as a monotherapy in 17 studies^35,38–53 and implemented in a multimodal intervention in 4 studies.^36,37,54,55 More information regarding the interventions of the included studies is available in eTable 2 in the Supplement.

Mean Effect Size, Heterogeneity, and Bias

A visual representation of the distribution of the study effect sizes is provided in the Figure. Seventeen of the 21 effect sizes (81%) were smaller than 0, indicating larger reductions in depressive symptoms for physical activity interventions.^{35–38,40,41,43–45,47–53,55} The physical activity interventions had a mean effect size of −0.29 (95% CI, −0.47 to −0.10; P = .004). Overall, the reduction in depressive symptoms after a physical activity intervention resulted in a number needed to treat of 6.

Only 4 studies^36,48,52,53 assessed the effects of physical activity interventions on depressive symptoms at follow-up. The mean follow-up period postintervention was 21 weeks (range, 6-48 weeks). No association of physical activity interventions with depressive symptoms was detected at follow-up (g = −0.39; 95% CI, −1.01 to 0.24; P = .14) (eFigure 2 in the Supplement).

There was evidence of moderate heterogeneity at postintervention (Q = 53.92; df = 20; P < .001; I² = 62.9% [95% CI, 40.7%-76.8%]) and at follow-up (Q = 7.85; df = 3; P = .04; I² = 61.8% [95% CI, 0.0%-87.2%]). Egger regression test revealed significant funnel plot asymmetry (intercept, −1.87 [95% CI, −3.20 to −0.55]; t = −2.77; P = .01) (eFigure 3 in the Supplement). Three outliers were detected. The differences in effect sizes may be attributed to different research designs^40,50 or a different study intervention.⁴⁷ We conducted sensitivity analyses after excluding these studies, resulting in a smaller effect size that remained significant (g = −0.15; 95% CI, −0.26 to −0.03; P = .02; I² = 25.8% [95% CI, 0.0%-58.1%]). Risk of bias was determined to be low in 6 studies,^{36,38,51–54} moderate in 13 studies,^{35,37,39–41,43–48,50,55} and high in 2 studies^42,49 (eFigure 4 in the Supplement). We repeated the analyses after removing studies with high risk of bias, which did not change the overall effect size (g = −0.29; 95% CI, −0.48 to −0.10; P = .005; I² = 65.4% [95% CI, 43.7%-78.7%]).

Moderator Analyses

The primary moderator analysis did not show significant moderation effects (QM = 8.12, df = 4, P = .09; R² = 49.0%; QE = 39.32, P = .001; I² = 42.8%) (Table 2). Total physical activity volume, study design, participant health status, and allocation and/or assessment concealment did not moderate the main treatment effect. Results of the secondary analyses are summarized in Table 3. In brief, interventions showed greater benefits in participants aged 13 years or older and those with a mental illness and/or depression diagnosis. Participant sex, supervision, and frequency and duration of the intervention also moderated the overall effect.

Discussion

In this meta-analysis, we investigated the association of physical activity interventions with depressive symptoms in children and adolescents. The results showed that physical activity interventions produced greater reductions in depressive symptoms compared with the control conditions. However, these differences were not detected after a mean follow-up of 21 weeks, possibly due to the limited number of studies with follow-up outcomes.

Comorbid psychiatric conditions develop in up to 90% of children and adolescents with depression, and 2 comorbid conditions develop in up to 50%.²⁴ As such, pediatric depression is often underdiagnosed and undertreated, with research showing that only 50% of children and adolescents with depression receive an adequate diagnosis before reaching adulthood.⁵⁶ Physical activity, particularly aerobic exercise, is suitable for children, as it is a major component of most sports activities and can easily be implemented in physical education classes. Increased levels of physical activity can reduce the risk of cardiovascular disease,⁵⁷ which is the leading cause of death in individuals with depression,⁵⁸ and improve executive function,⁵⁹ which is greatly impaired in youth with depression.⁶⁰ Most of the studies in this systematic review and meta-analysis involved a supervised school intervention targeted at increasing students’ physical activity levels through a wide range of activities, including sport games and simple aerobic exercises (eg, running, jumping). The findings of this systematic review and meta-analysis strengthen the role of physical activity for depressive symptom management and highlight the potential of structured physical education programs in primary and secondary schools for improving the mental health of children and adolescents.

While the association between physical activity and depression is strong,^61,62 the mechanisms underlying the antidepressant properties of physical activity remain unclear. Potential pathways include the activation of the endocannabinoid system to stimulate the release of endorphins,⁶³ an increase in the bioavailability of brain neurotransmitters (eg, serotonin, dopamine, noradrenaline) that are reduced with depression,⁶⁴ and long-term changes in brain plasticity.⁶⁵ Psychosocial and behavioral hypotheses have also been made, asserting that physical activity can lead to improvements in self-perception, social interactions, and self-confidence.⁶⁵ However, the depressive phenomenology is multifaceted, including cognitive, emotional, interpersonal, and somatic symptoms,⁶⁶ and isolating the effects that physical activity has on specific symptoms is seemingly impossible due to individual variability. Evidence on the benefits of physical activity in conjunction with traditional depression treatments is even more sparse, though it seems that physical activity can enhance the treatment of cognitive and affective symptoms in depression.⁶⁷ Furthermore, the combination of physical activity and pharmacotherapy may reduce relapse risk, improve adherence to antidepressants, and promote better management of adverse effects compared with pharmacotherapy alone.⁶⁷ The benefits of physical activity are not restricted to depression treatment but extend to various health domains, including psychiatric, neurologic, cognitive, somatic, and psychosocial.⁶⁸ Therefore, a combination of biologic, psychological, and psychosocial factors may mediate the relationship between physical activity and depression. More research is warranted to explain whether and how these mechanisms moderate the effect of physical activity and whether these changes are also present in younger populations.

Our moderator analyses showed that participants with a mental illness and/or a clinical diagnosis of depression benefitted more from the physical activity interventions compared with those who were healthy or had a physical illness. Similar results were observed in a meta-analysis on exercise for adult depression.¹⁴ As the authors concluded, participants showed greater depressive symptoms at baseline and may have had more potential for improvement than those whose symptoms were not indicative of a depression diagnosis. Our findings suggest that physical activity interventions may be particularly helpful in children and adolescents with elevated depressive symptoms.

Physical activity had greater benefits in participants aged 13 years or older than in younger participants. A recent cohort study reported that between the ages of 12 and 16 years, the physical activity levels of children start to decrease while sedentary time increases, and this was associated with more depressive symptoms.⁶⁹ It is possible that younger children are sufficiently active to be desensitized to additional physical activity, whereas their older and more sedentary counterparts might be more responsive to the intervention.

Three physical activity sessions per week and interventions that were shorter than 12 weeks induced greater benefits on depressive symptoms compared with other frequencies and durations. These findings are reflected in the results of previous meta-analyses on the association between physical activity and depression,^61,70 suggesting that increasing amounts of physical activity may not translate into greater reductions in depressive symptoms. A recent cross-sectional study found a U-shaped association between physical activity frequency and mental health, such that 10 to 15 sessions per month induced the greatest mental health improvements.⁷¹ In contrast, there is evidence that increasing amounts of physical activity have beneficial effects on mental health.⁷² With regard to overall intervention duration, Bailey et al⁷³ discussed the challenges in maintaining long-term benefits in interventional studies with children and adolescents and described the factors and skills needed to preserve these benefits. Securing participants’ attention throughout a trial can be difficult, and researchers may need to consider loss of interest in the intervention as a potential factor influencing the treatment effect. More research is needed to explain these findings and to establish the optimal physical activity parameters for depressive symptom management.

We found differences in the effect sizes of studies involving female-only participants and studies with unsupervised interventions compared with studies on both males and females and studies with supervised or partially supervised interventions. These findings are surprising and may be attributed to a discrepancy among the number of studies used to assess each moderator. Eighteen studies included boys and girls^{35–40,42–46,48,49,51–55} and 3 included female participants only,^41,47,50 and 16 studies^{35–37,39,41–43,45,47–49,51–55} reported fully supervised interventions, whereas 2 did not report any supervision.^40,50 Among the studies recruiting females only and the studies with unsupervised interventions, all but 1 were identified as potential outliers because of their substantially larger effect sizes.^40,47,50 Thus, their effect sizes may have been overestimated and may have influenced our estimate of the true difference between moderators.

Limitations

This study has some limitations. First, we did not screen for study quality in our inclusion criteria, and it is possible that poorly conducted studies may have influenced the overall results. Second, there was a notable lack of complete reporting regarding participant and trial characteristics. Specifically, information regarding the blinding of participants and assessors, exercise intensity, exercise type, and degree of supervision was often absent and had to be extrapolated from the article, requested from authors, or otherwise excluded from the analyses. Future research should include more rigorous reporting of study design and characteristics to allow for the analysis of potential moderators on the treatment effects. Third, because of the exploratory nature of our univariable meta-regression analyses, other confounding variables could not be controlled for, which limits the interpretation of our findings and warrants further validation.

Conclusions

The results of this systematic review and meta-analysis suggest that physical activity interventions can alleviate symptoms of depression in children and adolescents. Results were corroborated by stringent sensitivity and moderator analyses that revealed greater reductions in depressive symptoms in participants aged 13 years or older and in those with a mental illness and/or depression diagnosis. Future studies should investigate the influence of physical activity parameters such as frequency, duration, and supervision of the sessions to determine the optimal dose and mode of delivery of the intervention for depressive symptom management.

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Article Information

Accepted for Publication: September 21, 2022.

Published Online: January 3, 2023. doi:10.1001/jamapediatrics.2022.5090

Corresponding Author: Parco M. Siu, PhD, Division of Kinesiology, School of Public Health, The University of Hong Kong, Pokfulam, Hong Kong 852, China (pmsiu@hku.hk).

Author Contributions: Mr Recchia had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Recchia, Bernal, Fong, S. H. Wong, Chung, Chan, Capio, S. W. Wong, Chen, Siu.

Acquisition, analysis, or interpretation of data: Recchia, Bernal, Yu, Sit, Chen, Thompson, Siu.

Drafting of the manuscript: Recchia, S. H. Wong, Thompson, Siu.

Critical revision of the manuscript for important intellectual content: Recchia, Bernal, Fong, Chung, Chan, Capio, Yu, S. W. Wong, Sit, Chen, Siu.

Statistical analysis: Recchia, Fong, S. H. Wong, Chen, Siu.

Obtained funding: Chan, Capio, Siu.

Administrative, technical, or material support: Chan, Thompson, Siu.

Supervision: Fong, S. W. Wong, Chen, Siu.

Conflict of Interest Disclosures: None reported.

Funding/Support: This work was supported by grant 17182461 from 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.

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: The authors thank Edwin Chin, PhD, The Chinese University of Hong Kong, for the technical advice provided for the conduct of this study. He did not receive compensation for his contribution.

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