“…Both population and clinical surveys (Ball and Ross, 1991;Caetano and Weisner, 1995;Helzer and Pryzbeck, 1988;Martin et al, 1996;Tsuang et al, 1994;Regier et al, 1990) indicate that the majority of those with a current substance use disorder use multiple psychoactive substances and meet current or lifetime criteria for a number of substance use disorders. For example, estimates indicate that 30-60% of alcoholdependent individuals abuse cocaine (Caetano and Weisner, 1995;Martin et al, 1996;Tsuang et al, 1994), 20-50% abuse marijuana (Caetano and Weisner, 1995;Martin et al, 1996;Tsuang et al, 1994), 12-20% abuse benzodiazepines (Ciraulo et al, 1988;Ross, 1993) and 7-10% abuse heroin (Caetano and Weisner, 1995;Martin et al, 1996;Tsuang et al, 1994).…”