disorder (ASPD) or ASPD DSM-III-R criteria modified to match ASPD DSM-IV criteria. Because ASPD is only assessed in those 18 years and older, DSM-III-R or DSM-IV conduct disorder (CD) criteria were substituted for those under 18. Because ASPD and CD have different numbers of criteria, CD criterion counts were proportionally scored in order to create a comparable range (0-7) with ASPD scores (e.g., a participant endorsing 7/15 CD criteria would receive a proportional score of 3.23/7). Illicit drug dependence and abuse were measured with separate sum scores of DSM-IV cocaine, marijuana, sedatives, stimulants, opiates, and other drugs dependence and abuse criterion counts. For participants with data on the alcohol and illicit drug dependence and abuse and antisocial behavior variables [2148 individuals (93%) in the family-based sample, 47% male], we extracted component scores from a principal components analysis. A single component accounted for 68% of the common variance among the externalizing disorder variables with the following loadings: alcohol dependence, 0.86; alcohol abuse, 0.86; antisocial behavior, 0.80; illicit drug dependence, 0.82; illicit drug abuse, 0.79.
