Treatment-seeking PSU (n = 19) and ALC (n = 117) were recruited from the San Francisco VA Medical Center and Kaiser Permanente. For statistical reasons, we reduced our large ALC cohort to 40 individuals by matching them on age, education, smoking status and drinking variables to the smaller PSU group. Both ALC and PSU participants completed the structured clinical interview for the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) Axis I Disorder Patient Edition, Version 2.0 (First, et al., 1998). Prior to enrollment, male participants consumed more than 150 alcoholic drinks (one drink contains 13.6 g of ethanol) per month for at least 8 years; females consumed more than 80 drinks per month for at least 6 years. PSU individuals were diagnosed with both alcohol dependence and dependence on at least one psychostimulant, with or without nicotine dependence and cannabis use disorder. All PSU met DSM-IV dependence criteria for at least one illicit substance and 10.5% met criteria for cannabis use disorder. Specifically, 12 PSU met criteria for cocaine dependence (63%) and 2 of these were either abusing or
