Potential participants first met individually with research staff to have the study explained, give written informed consent, and respond to a screening questionnaire that was used to gather information on demographics, personal medical history, ethnicity and detailed measures of substance abuse history (Schuckit, 1985) and weight & height. Each participant also completed an interview with the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) (Bucholz et al., 1994) which was used to make diagnoses (American Psychiatric Association, 1994). The SSAGA is a fully structured, poly-diagnostic psychiatric interview that has undergone both reliability and validity testing (Bucholz et al., 1994; Hesselbrock et al., 1999). It has been successfully used in Native American populations previously (Gilder et al., 2004; Hesselbrock et al., 2000). Interviewers were all trained by personnel from the Collaborative Study on the Genetics of Alcoholism (COGA). All best final diagnoses were made by a research psychiatrist/addiction specialist, trained in the SSAGA. The three externalizing phenotypes were: 1) DSM-III-R Antisocial personality disorder (requires childhood CD to make the diagnosis), 2) DSM-III-R conduct disorder with no diagnosis of adult ASPD, and 3) The combined phenotype of participants with either 1) or 2) e.g. DSM-III-R conduct disorder/or Antisocial personality disorder.
