Children's genotypes interact with maternal responsive care in predicting children's competence: diathesis-stress or differential susceptibility?

We examined Genotype × Environment (G × E) interactions between children's genotypes (the serotonin transporter linked promoter region [5-HTTLPR] gene) and maternal responsive care observed at 15, 25, 38, and 52 months on three aspects of children's competence at 67 months: academic skills and school engagement, social functioning with peers, and moral internalization that encompassed prosocial moral cognition and the moral self. Academic and social competence outcomes were reported by both parents, and moral internalization was observed in children's narratives elicited by hypothetical stories and in a puppet interview. Analyses revealed robust G × E interactions, such that children's genotype moderated the effects of maternal responsive care on all aspects of children's competence. Among children with a short 5-HTTLPR allele (ss/sl), those whose mothers were more responsive were significantly more competent than those whose mothers were less responsive. Responsiveness had no effect for children with two long alleles (ll). For academic and social competence, the G × E interactions resembled the diathesis-stress model: ss/sl children of unresponsive mothers had particularly unfavorable outcomes, but ss/sl children of responsive mothers had no worse outcomes than ll children. For moral internalization, the G × E interaction reflected the differential susceptibility model: whereas ss/sl children of unresponsive mothers again had particularly unfavorable outcomes, ss/sl children of responsive mothers had significantly better outcomes than ll children.