Involvement in Sports, Hippocampal Volume, and Depressive Symptoms in Children.

Background: Recent studies have found that higher levels of exercise are associated with fewer symptoms of depression among young people. In addition, research suggests that exercise may modify hippocampal volume, a brain region that has been found to show reduced volume in depression. However, it is not clear whether this relationship emerges as early as preadolescence.

Methods: We examined data from a nationwide sample of 4191 children 9 to 11 years of age from the Adolescent Brain and Cognitive Development Study. The parents of the children completed the Child Behavior Checklist, providing data about the child's depressive symptoms, and the Sports and Activities Questionnaire, which provided data about the child's participation in 23 sports. Children also took part in a structural magnetic resonance imaging scan, providing us with measures of bilateral hippocampal volume.

Results: Sports involvement interacted with sex to predict depressive symptoms, with a negative relationship found in boys only (t = -5.257, β = -.115, p < .001). Sports involvement was positively correlated with hippocampal volume in both boys and girls (t = 2.810, β = .035, p = .007). Hippocampal volume also interacted with sex to predict depressive symptoms, with a negative relationship in boys (t = -2.562, β = -.070, p = .010), and served as a partial mediator for the relationship between involvement in sports and depressive symptoms in boys.

Conclusions: These findings help illuminate a potential neural mechanism for the impact of exercise on the developing brain, and the differential effects in boys versus girls mirror findings in the animal literature. More research is needed to understand the causal relationships between these constructs.