MODELING GENETIC AND ENVIRONMENTAL-INFLUENCES IN THE ETIOLOGY OF CONDUCT DISORDER - A STUDY OF 2,682 ADULT TWIN PAIRS

The etiology of conduct disorder (CD) was examined retrospectively in a sample of 2,682 male, female, and unlike-sex adult twin pairs from t he community-based Australian Twin Register. Model-fitting analyses in dicated a substantial genetic influence on risk for CD, accounting for 71% of the variance (95% confidence interval [CI] = 32-79%). There wa s not a statistically significant effect of the shared environment in the best-fitting model of CD, but a modest effect of the shared enviro nment on the risk for CD could not be rejected (95% CI = 0-32%). The m agnitude of generic and environmental influences for CD liability did not vary significantly for boys and girls, and the specific genetic an d environmental mechanisms important for the development of CD appeare d to be largely the same for both sexes. The fit of a multiple-thresho ld model raises the possibility that CD may not necessarily be a discr ete entity but rather an extreme of the normal variation in conduct-di sordered behavior found in the general population.