Additional evidence against shared environmental contributions to attention-deficit/hyperactivity problems.

Department of Psychology, Michigan State University, 107D Psychology Building, East Lansing, MI, 48824, USA, .
Behavior Genetics (Impact Factor: 2.84). 05/2012; 42(5):711-21. DOI: 10.1007/s10519-012-9545-y
Source: PubMed

ABSTRACT A recent meta-analysis "Burt (Psychol Bull 135:608-637, 2009)" indicated that shared environmental influences (C) do not contribute to Attention-Deficit/Hyperactivity Disorder (ADHD). Unfortunately, the meta-analysis relied almost exclusively on classical twin studies. Although useful in many ways, some of the assumptions of the classical twin model (e.g., dominant genetic and shared environmental influences do not simultaneously influence the phenotype) can artifactually decrease estimates of C. There is thus a need to confirm that dominant genetic influences are not suppressing estimates of C on ADHD. The current study sought to do just this via the use of a nuclear twin family model, which allows researchers to simultaneously model and estimate dominant genetic and shared environmental influences. We examined two independent samples of child twins: 312 pairs from the Michigan State University Twin Registry and 854 pairs from the PrE School Twin Study in Sweden. Shared environmental influences were found to be statistically indistinguishable from zero and to account for less than 5 % of the variance. We conclude that the presence of dominant genetic influences does not account for the absence of C on ADHD.

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    ABSTRACT: Although few would now contest the presence of Gene × Environment (G × E) effects in the development of child psychopathology, it remains unclear how these effects manifest themselves. Alternative G × 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 × E. Results highlight the utility of child twin samples in testing different manifestations of G × E effects.
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