of SUD diagnoses for alcohol (6-5.88%), marijuana (3.81-3.70%), and tobacco dependence (3.46-2.37%); based on this observation we chose not to impose clustering. Unlike the experimentation and repeated-use categories, DSM-IV abuse and dependence are mutually exclusive diagnoses, such that a diagnosis of dependence precludes a diagnosis of abuse. Furthermore, abuse and dependence (with and without physiological symptoms) are both outcomes of drug use; as such we created a composite measure, lifetime SUD, that indicated the presence or absence of an abuse or dependence diagnosis.
