Both factor and IRT analyses indicated the utility of conceptualizing DSM-IV cannabis abuse and dependence criteria along a dimensional scale of severity. Regardless of whether the cannabis use criterion was entered into the model, factor analyses results indicated that a one-factor model provided a good fit to the data. IRT results showed that the diagnostic criteria for cannabis abuse and dependence (with or without the cannabis use criterion) can be effectively modeled along a unidimensional latent trait of cannabis use disorder severity, and that these results remained invariant across sex. These results are similar to those found for other studies examining cannabis use criteria using IRT analyses among adult (Teesson et al., 2002; Gillespie et al., 2006; Langenbucher et al., 2004; Lynskey and Agrawal, 2007) and adolescent samples (Martin et al., 2006).
