On the other hand, one limitation includes investigation of a single plasticity gene, in contrast to several susceptibility genes (for example, DRD4)18, 22 or a cumulative genetic plasticity index comprised of several genes.19 Although we purposefully selected 5-HTTLPR a priori as the susceptibility gene based on prior theoretical and empirical research,25, 31, 64, 65 highlighting its likely function as a plasticity gene that is responsive to differing environmental contexts, future research would benefit from replicating these findings and extending them with other theoretically grounded plasticity genes. A second limitation is the use of correlational design rather than experimental manipulation of environmental context. Future research could investigate parenting interventions shown to enhance positive, supportive parenting58 in the context of a genetically ascertained sample to investigate whether youth carrying plasticity genes respond with enhanced positive affect to supportive parenting. Last, putative mechanisms underlying the demonstrated GxE remain unknown and untested. One possible reason that youth carrying two short alleles of 5-HTTLPR are more susceptible to the full dimension of parenting is, genes involved in serotonergic system functioning are likely implicated in reward
