Previous studies have shown that there is considerable diagnostic overlap between the DSM-IV criteria for abuse and dependence (Langenbucher and Chung, 1995; Langenbucher et al., 1995). Even factor analytic (FA) studies that report a 2-factor model do not yield complete differentiation between abuse and dependence criteria (Grant et al., 2007; Harford and Muthén, 2001; Muthén, 1995). Multiple-factor models consistently yield one large factor and one or two minor factors that are highly correlated with the first factor, confirming that 2-factor models do not replicate the DSM-IV distinction between dependence and abuse criteria. Clinical studies report evidence for both 1- and 2-factor models, but in view of the high correlation between abuse and dependence, many clinicians favor a single factor as more appropriate in treatment samples (Feingold and Rounsaville, 1995; Langenbucher, 2004). More recent applications of item response theory (IRT) indicate that abuse and dependence criteria each tap into both mild and more severe symptom pathology in adults (Kahler et al., 2006; Krueger et al., 2006; Langenbucher et al., 2004; Saha et al., 2006; Saha et al., 2007) as well as in clinical samples of adolescents (Martin et al., 2006).
