Subtypes for classifying adolescents with marijuana use disorders: construct validity and clinical implications

Aims To evaluate the construct and predictive validity of six different subtyping classifications selected on the basis of their empirical support in the literature on adolescent substance abuse. Methods Typological data were collected from a heterogeneous sample of 600 adolescents presenting for marijuana treatment. The classification schemes onset age, family history, externalizing disorders, internalizing disorders and temperament. Subgroups were compared in terms of substance use frequency, substance abuse problems, social support for substance use, family conflict, school problems and negative peer associations. Results Each of the categorical classification schemes differentiated subtypes significantly on some or all of the construct validation measures after controlling for demographic factors, thereby indicating that each has valuable explanatory power from a theoretical perspective. Externalizing disorders, onset age, difficult temperament and internalizing disorders continued to add unique variance to discrimination after the effects of the other subtypes had been removed. At 12-month follow-up there were no differences between subtypes on substance use frequency, but adolescents with higher levels of externalizing disorders and internalizing disorders continued to experience more substance use problems. Conclusion Categorical subtypes may have particular relevance to the development of treatment interventions as well as prevention measures.