The serotonin transporter promoter polymorphism, 5-HTTLPR, interacted with parenting behaviors to predict youths' level of positive affect. Consistent with our a priori hypothesis based on the DSH framework, the association between positive/supportive parenting and youths' positive affect varied as a function of youths' 5-HTTLPR genotype. Youth carrying two functional short copies of 5-HTTLPR exhibited significantly lower levels of positive affect in an environmental context of unsupportive parenting in all the three studies, and significantly higher levels of positive affect in positive, supportive parenting contexts in studies 1 and 3, as indicated by the regions of significance. In contrast, youth carrying the L' allele of 5-HTTLPR (that is, L'S' and L'L' genotypes) showed relatively consistent levels of positive affect across both the supportive and unsupportive parenting environments. This pattern aligns with the DSH in that genetically susceptible individuals respond to their environment in a ‘for better and worse' manner, in which outcomes are enhanced under enriched environments and are poorest under risk environments. Importantly, this GxE pattern was consistently found in three independent samples, in which both parenting behaviors and positive
