A number of recent studies have employed item response theory (IRT) models, sometimes called latent trait models, to study the severity of AUD. After confirming the unidimensionality of a set of alcohol problem items, e.g., AUD symptoms or criteria, these models estimate parameters that reflect the relative severity of each item along a continuum of AUD severity. Two-parameter models also estimate how effectively each item discriminates individuals at different levels of severity. A recent study using data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) established that the 11 DSM-IV (American Psychiatric Association, 1994) abuse and dependence criteria were interspersed in terms of severity. Some of the abuse criteria (e.g., interpersonal problems caused by drinking) lay at the highest end of the severity scale and some of the dependence criteria (e.g., tolerance and withdrawal) lay at the lowest end, thus calling into question the DSM-IV hierarchy of abuse and dependence (Saha et al., 2006). Likewise, Proudfoot et al. (2006) found that the abuse criteria of hazardous drinking legal problems and drinking despite social/interpersonal problems were among the
