Externalizing factor scores were computed from dimensional symptom summary scores on the lifetime alcohol abuse and dependence, cannabis abuse and dependence, cocaine abuse and dependence, and adult anti-social personality disorder modules of the Structured Clinical Interview for DSM-IV disorders (First et al., 1994) and the SCID-II (First et al., 1995). To obtain dimensional scores for each SCID-assessed diagnosis, we administered all symptoms within a module and anchored them temporally to a consistent time period to ensure that the rated symptoms were defined as co-occuring. In a subset of participants, adult antisociality was assessed using the International Personality Disorders Exam (IPDE) (Loranger, 1999). Overlapping items from the SCID and IPDE measures of antisocial personality disorder were then standardized and combined to form a single adult antisociality symptom score for analysis. Summary scores on adult antisociality, alcohol abuse/dependence, cannabis abuse/dependence, and cocaine abuse/dependence were then submitted to a confirmatory factor analysis which specified that a latent externalizing factor underlied the variance and co-variance of the symptom summary scores for these variables. This model fit the data well per fit indices and all
