Although considerable prior research shows that dysregulation of positive emotion systems and difficulties upregulating positive affect are implicated in psychopathology, scant research investigated both molecular genetic and environmental interactions contributing to the positive affect in youth. Our GxE results refine and potentially clarify prior, inconsistent main effect association studies that sought to demonstrate links between 5-HTTLPR and psychiatric disorder (for example, depression).57 Our findings suggest that 5-HTTLPR may be a plasticity gene25 that confers responsivity to environmental inputs. Previously equivocal GxE findings in depression,36 focused on 5-HTTLPR as purely a risk gene in the context of negative environments, may have occurred because a differential susceptibility model may best capture the relationship between the environmental conditions and genetic risk in a ‘for better and worse' manner. Likewise, prior research shows that negative/unsupportive parenting behavior is associated with risk to psychopathology16 and poor socio-emotional health.14 Our results suggest that these simple main effect associations can be refined, and prediction of psychopathology can be improved by joint consideration and co-action of genetic plasticity under negative environmental conditions.
