Exercise in Adolescent Depression: Fitness, Clinical Outcomes, and BDNF

Introduction: Despite the initiation of treatment for depression including medications and evidence-based psychotherapies, many adolescents continue to have depressive symptoms. A 2017 meta-analysis of exercise research for this population summarized that physical activity appears to improve depression symptoms in adolescents, but the need for larger trials was emphasized. Most importantly, the physiological and neurological mechanisms of action through which exercise exerts its antidepressant effects must be explored. Objectives: The objective of this study was to assess the feasibility of a group exercise intervention for adolescents with depressive disorders. To investigate physiologic changes, serum biomarkers were examined including brain-derived neurotrophic factor (BDNF). Secondary analyses explored relationships among depressive symptoms, exercise self-efficacy, and fitness. Methods: Adolescents with depression (Children's Depression Rating Scale-Revised, CDRS-R ≥ 40) participated in a group intervention for 12 weeks of aerobic exercise (1X in group and 2X independently each week). Blood draws were taken pre- and post-intervention. At weeks 1 and 12, the Balke Fitness Test was administered measuring exertion ratings and heart rates during treadmill activity. Results: Participants had a significant decrease in depressive symptoms over the 12-week intervention. Mean CDRS-R score of completers was 52.2 at baseline and 29.6 post-intervention, for a decrease of 22.5 points. Paired samples t-tests showed that the decrease in CDRS-R scores from baseline to week 12 was statistically significant [t(12)=9.12, p