The DSM-5 Task Force asked work groups for severity indicators of diagnoses (mild, moderate, or severe). Many severity indicators are possible (e.g., levels of use, impairment, or comorbidity), and the Substance-Related Disorders Work Group sought a simple, parsimonious approach. A count of the criteria themselves serves this purpose well, since as the count increases so does the likelihood of substance use disorder risk factors and consequences (89–91, 98). The work group considered weighting the count by item response theory severity parameters, but comparing the association of weighted and unweighted criterion counts to consumption, functioning, and family history showed no advantage for weighting (98). Furthermore, since severity parameters differ somewhat across samples (31), no universal set of weights exists.
