All participants completed a detailed semi-structured interview that incorporated methods of the time-line followback procedure and assessed patterns of substance use for 13 different substance classes, similar to methods employed in other studies (e.g., Gonzalez, 2004; Rippeth et al., 2004 (link)). For each substance queried, participants were asked about frequency and quantity of use across various epochs in their lifetime to arrive at estimates of cumulative lifetime use, as well as amount and frequency of use in the 12 months and in the 30 days prior to their evaluation. The substance use module of the Structured Clinical Interview for DSM-IV (SCID) was administered to diagnose the presence of alcohol and substance use disorders during participants’ lifetime and in the 30 days prior to their evaluation (First et al., 2002 ). We assessed for the presence and severity of symptoms associated with cannabis addiction with the Marijuana Severity Index (MSI; Alexander, 2003 (link)): a 31 yes/no forced-choice questionnaire on problematic patterns of cannabis use that a participant has “ever” experienced from cannabis use. We also quantified severity of cannabis addiction by tabulating the total number of current DSM-IV symptoms of cannabis abuse and dependence endorsed by a participant in the 30 days prior to their evaluation (DSM-IV CUD symptoms).