Differential susceptibility to rearing environment depending on dopamine-related genes: new evidence and a meta-analysis.

In the current paper we present new empirical data and meta-analytic evidence for the role of dopamine-related genes as a susceptibility factor interacting with the rearing environment for better and for worse, that is, increasing children's susceptibility to both the adverse effects of unsupportive environments and the beneficial effects of supportive rearing. In Study 1 we examined the readiness of 91 7-year-old children to donate their money to a charity (UNICEF). We tested whether the association between attachment and donating behavior was moderated by the presence of the dopamine receptor D4 (DRD4) 7-repeat allele. The attachment story completion task was used to assess attachment as an index of the quality of the rearing environment. Children with secure attachment representations donated more but only if they had the DRD4 7-repeat allele. In Study 2 we present the results of a meta-analysis of gene-environment studies on children up to 10 years of age involving dopamine-related genes (dopamine receptor D2, DRD4, dopamine transporter). The cumulative negative effects of these "risk genes" and adverse rearing environments have been stressed, but potentially cumulative positive effects of these same genes interacting with positive rearing environments remained largely unnoticed. We examined the associations between negative and positive rearing environments and developmental outcomes as moderated by dopamine-related gene polymorphisms. Children with the less efficient dopamine-related genes did worse in negative environments than the comparisons without the "genetic risk," but they also profited most from positive environments. Findings are discussed in light of evolutionary theory, and illustrated with some practical implications of differential susceptibility.