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 longit udinal patterns of alcohol-tobacco use disorder comorbidity. Participants w ere 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 ti me were identified: nondiagnosing; developmentally limited alcohol use diso rder; chronic alcohol use disorder; chronic tobacco use disorder; and comor bid 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 l atent classes. Conclusions: Characterizations of alcohol use disorders typically fail to c onsider important sources of heterogeneity such as course or comorbidity. B y simultaneously modeling developmental course and comorbidity with tobacco dependence, we were able to identify distinct trajectories of single and c oncurrent substance use disorders. Such multi-substance trajectories repres ent meaningful subtypes that, although sharing substantial common influence s, have unique etiologic correlates. Additionally, these subtypes might rep resent distinct groups from the perspective of intervention strategies.