The genetic risk for externalizing disorders was a composite measure of the co-twin self-report symptoms of DSM-IV conduct disorder (obtained at MM1 and MM2) and antisocial personality disorder (MM2) (APA, 1994), and twin report of antisocial personality disorder in their co-twin and father using Family History-Research Diagnostic Criteria (Muffler et al. 1991) (MM2). The contribution of each measure to the total genetic risk for externalizing disorders was based on the modified ridit score as described above. The product-moment correlation between our measures of the genetic risk for AUDs and for externalizing disorders was +0.39.
