Parental Involvement Moderates Etiological Influences on Attention Deficit Hyperactivity Disorder Behaviors in Child Twins

Although few would now contest the presence of Gene 9 Environment (G 9 E) effects in the development of child psychopathology, it remains unclear how these effects manifest themselves. Alternative G 9 E models have been proposed (i.e., diathesis–stress, differential susceptibility, bioecological), each of which has notably different implications for etiology. Child twin studies present a powerful tool for discriminating between these models. The current study examined whether and how parental involvement moderated etiological influences on attention deficit hyperactivity disorder (ADHD) within 500 twin pairs aged 6–11 years. Results indicated moderation of genetic and nonshared environmental contributions to ADHD by parental involvement, and moreover, suggested both differential susceptibility and bioecological models of G 9 E. Results highlight the utility of child twin samples in testing different manifestations of G 9 E effects. Attention deficit hyperactivity disorder (ADHD) is a common and costly neurodevelopmental disorder characterized by excessive and developmentally inappropriate symptoms of inattention–disorganiza-tion and hyperactivity–impulsivity (American Psy-chiatric Association, 2013). Past behavioral geneti