Trajectories of concurrent substance use disorders: a developmental, typological approach to comorbidity.

BACKGROUND: Although alcohol and tobacco use disorders are highly comorbid, little is known regarding the combined course of these disorders.
METHODS: The current study utilized latent class analysis to examine longitudinal patterns of alcohol-tobacco use disorder comorbidity. Participants were 449 young adults (baseline age, 18.5 years; 48% male; 51% with paternal history of alcoholism) assessed five times over 7 years.
RESULTS: Five longitudinal types of alcohol or tobacco use disorder over time were identified: nondiagnosing; developmentally limited alcohol use disorder; chronic alcohol use disorder; chronic tobacco use disorder; and comorbid alcohol and tobacco use disorder. These typologies were distinguishable on the basis of family history of alcoholism status and sex. Etiologically important third variables (alcohol expectancies, behavioral undercontrol, childhood stressors) mediated the relation between family history and the latent classes.
CONCLUSIONS: Characterizations of alcohol use disorders typically fail to consider important sources of heterogeneity such as course or comorbidity. By simultaneously modeling developmental course and comorbidity with tobacco dependence, we were able to identify distinct trajectories of single and concurrent substance use disorders. Such multi-substance trajectories represent meaningful subtypes that, although sharing substantial common influences, have unique etiologic correlates. Additionally, these subtypes might represent distinct groups from the perspective of intervention strategies.