Few studies have utilized IRT to compare multiple substances as part of a single dimension. In a study of poly-substance disorder severity, Kirisci and colleagues (2006) found that substance use diagnoses displayed different location and discrimination parameters between sexes (husbands and wives) as well as between ages (fathers and adolescent sons). As with models of substance-specific DSM criteria, disorder diagnoses indicated greater trait severity and provided more information in adult females and adolescent males than in adult males.
