The Effect of Exercise Training on Anxiety Symptoms in Children and Adolescents: A Systematic Review and Meta-Analysis of Randomized Trials.

Elevated anxiety symptoms and disorders affect ~10% to 20% of US children and adolescents annually, which contributes to developmental disturbances in social, emotional, and cognitive domains. Although preliminary evidence (primarily in adults) suggests that exercise may be a promising therapeutic approach for lowering anxiety among children and adolescents, sufficient meta-analytic evidence is lacking. The aim of this study was to estimate the population effect of exercise training on anxiety levels in children and adolescents, and to test the extent to which effects vary based on features of the exercise stimulus (e.g., exercise intensity, mode, duration, frequency) and participant characteristics (e.g., age, sex, clinical vs. nonclinical samples). Included studies were: (1) peer-reviewed publications, (2) published in English, (3) included youth participants < 20 years of age, (4) measured the change in anxiety symptoms in a no-treatment control and exercise-only treatment group, or a combined treatment group from which an independent effect of exercise could be estimated, and (5) reported results as mean and standard deviation, standard error, or 95% confidence intervals (CI) from which an effect size could be calculated. A standardized mean difference effect size (ES; Hedges' d) was calculated by subtracting the mean change in the control condition from the mean change in the exercise condition and dividing the difference by the pooled standard deviation of baseline values. Random effects models were used to aggregate a mean ES and 95% confidence interval using a three-level meta-analysis model structure to adjust for between-study variance and the correlation between effects nested within studies. Random effects meta-regression was used to explore potential sources of variability. In total, 39 effects derived from 22 studies published between 1982 and 2023 showed that exercise training significantly reduced anxiety symptoms by a moderate-sized magnitude (ES = 0.71, 95% CI: 0.36 to 1.06; p < 0.001). The majority of effects (k = 28, 71.79%) were larger than zero and ranged from -0.26 to 2.82. Moderator analyses indicated that mean effect size significantly varied based on exercise training intensity (p = 0.032); stronger magnitude reductions in anxiety symptoms were found for moderate- and high-intensity training (k = 28, ES = 0.88, 95% CI: 0.45 to 1.31) compared to low-intensity training (k = 11, ES = 0.21, 95% CI: -0.03 to 0.45). No other moderators significantly influenced the relationship between exercise and anxiety. Exercise training resulted in a moderate-sized, potentially clinically meaningful, mean reduction in anxiety symptoms among children and adolescents, with larger effects found for moderate- and high-intensities, supporting exercise training as a promising therapeutic approach to lower anxiety symptoms among children and adolescents. Future research is needed to address methodological limitations present in the included studies, including measured and reported details about the exercise stimulus, the use of assessments with stronger evidence to support their reliability and validity, and testing of plausible mechanisms for anxiety-reducing effects after exercise training. Trial Registration: PROSPERO registration number: CRD42024511605.