Proportion of children with presence of antisocial outcome was plotted as a function of degree of familial liability and degree of maltreatment (none versus reported versus substantiated and/or placed in foster care) for each of the research samples (MOTWIN and COGA). Since, in the twin sample, affectation status of twin A was used to predict affectation status of twin B (and vice versa) subsequent analyses of the twin data considered the pair as the unit of observation , randomly selecting one twin from each pair to depict outcome, and the co-twin to parameterize familial risk. Comparisons of MZ versus DZ twins were performed to capture variation in outcome exclusively as a function of inherited liability; for this, we employed contingency table analysis, adjusting for zip code clustering.
