We examined the effects of genotype and variation in early physically harsh parenting on externalizing behavior, which was measured as a function of multiple reports of aggression and delinquency from early childhood through early adulthood. Our findings support the existence of a GxE interaction between MAOA uVNTR genotype and harsh parenting; specifically, males carrying a low-activity risk allele are more sensitive to the effects on their delinquency of physical discipline than are males who do not carry the risk allele.
