For MOTWIN, a child or co-twin was designated affected if his/her total externalizing problem score fell at or above 60T on the parent-report CBCL (the published cutoff for clinical-level symptomatology for the overarching total internalizing and total externalizing problem domains; T-scores account for normal variation as a function of gender and age). For COGA, boys were designated affected if, at the time of assessment, they met three DSM-IIIR criteria for Conduct Disorder (CD); girls were designated affected if they met two DSM-IIIR criteria for CD. This gender-specific designation of affectedness ensures an approximately equal prevalence for boys- and girls-affected, and is consistent with prior research indicating that the psychosocial prognosis of girls with two CD symptoms is as poor as that for boys with three CD symptoms. [29]
