Brain-Derived Neurotrophic Factor Val66Met and Behavioral Adjustment after Early Childhood Traumatic Brain Injury.

The present study examined the differential effect of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism on behavioral adjustment in children with traumatic brain injury (TBI) relative to children with orthopedic injury (OI). Participants were drawn from a prospective, longitudinal study of children who sustained a TBI (n = 69) or OI (n = 72) between 3 and 7 years of age. Parents completed the Child Behavior Checklist (CBCL) at the immediate post-acute period, 6, 12, and 18 months after injury, and an average of 3.5 and 7 years after injury. Longitudinal mixed models examined the BDNF Val66Met allele status (Met carriers vs. Val/Val homozygotes) × injury group (TBI vs. OI) interaction in association with behavioral adjustment. After adjusting for continental ancestry, socioeconomic status, time post-injury, and pre-injury functioning, the allele status × injury group interaction was statistically significant for Internalizing, Externalizing, and Total Behavior problems. Post hoc within-group analysis suggested a consistent trend of poorer behavioral adjustment in Met carriers relative to Val/Val homozygotes in the TBI group; in contrast, the opposite trend was observed in the OI group. These within-group differences, however, did not reach statistical significance. The results support a differential effect of the BDNF Val66Met polymorphism on behavioral adjustment in children with early TBI relative to OI, and suggest that the Met allele associated with reduced activity-dependent secretion of BDNF may impart risk for poorer long-term behavioral adjustment in children with TBI.