The computer-assisted telephone interview was based on a modified version of the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA-OZ; Bucholz et al. 1994; Heath et al. 1997). The revised version of the SSAGA obtained more diagnostic information on cannabis and other illicit drug abuse and dependence, and questions assessing cannabis use disorders were supplemented with detailed questions, based on those described by Budney et al. (2004), to assess potential symptoms of withdrawal.
