BDNF genotype moderates the relation between physical activity and depressive symptoms.

OBJECTIVE To test whether the BDNF gene interacts with exercise to predict depressive symptoms. Physical activity is associated with a range of positive health outcomes, including fewer depressive symptoms. One plausible mechanism underlying these findings involves Brain-Derived Neurotrophic Factor (BDNF), a protein hypothesized to limit or repair the damage caused by stress. Physical activity increases expression of BDNF, which may enhance brain health. BDNF expression is controlled by the BDNF gene. Compared with individuals without a BDNF met allele, met-allele carriers have a lower expression of BDNF, which has been associated with Major Depressive Disorder. DESIGN Eighty-two healthy adolescent girls were genotyped for the BDNF val66met polymorphism, and their depressive symptoms and physical activity were assessed using questionnaires. MAIN OUTCOME MEASURES BDNF genotype, Children's Depression Inventory, and the Physical Activity Questionnaire for Older Children and Adolescents. RESULTS The BDNF polymorphism was found to moderate the relation between exercise and depressive symptoms: being physically active was protective for girls with a BDNF met allele (fewer depressive symptoms) but not for girls with the val/val polymorphism. CONCLUSION By integrating psychological and biological factors, the present study enhances our understanding of how physical activity contributes to resilience to psychopathology.