Parental brain-derived neurotrophic factor genotype, child prosociality, and their interaction as predictors of parents' warmth

Background: Parental warmth has been associated with various child behaviors, from effortful control to callous-unemotional traits. Factors that have been shown to affect parental warmth include heritability and child behavior. However, there is limited knowledge about which specific genes are involved, how they interact with child behavior, how they affect differential parenting, and how they affect fathers. We examined what affects paternal and maternal warmth by focusing on the child's prosocial behavior and parents' genotype, specifically a Valine to Methionine substitution at codon 66 in the brain-derived neurotrophic factor (BDNF) gene. Methods: Data was available from a sample of 6.5 year-old twins, consisting of 369 mothers and 663 children and 255 fathers and 458 children. Self-reports were used to assess mothers' and fathers' warmth. Child prosociality was assessed with the other-parent report and experimental assessments. Results: Mothers' warmth was not affected by their BDNF genotype, neither as a main effect nor in an interaction with child prosociality. Fathers with the Met allele scored higher on warmth. Additionally, there was a significant interaction between fathers' BDNF genotype and child prosociality. For fathers with the Met allele there was a positive association between warmth and child prosociality. Conversely, for fathers with the Val/Val genotype there was no association between warmth and child prosociality. Results were repeated longitudinally in a subsample with data on age 8-9 years. A direct within family analysis showed that fathers with the Met allele were more likely than Val/Val carriers to exhibit differential parenting toward twins who differed in their prosocial behavior. The same pattern of findings was found with mother-rated and experimentally assessed prosociality. Conclusions: These results shed light on the genetic and environmental underpinnings of paternal behavior and differential parenting.