Prospective analysis of comorbidity: tobacco and alcohol use disorders.

Alcohol use disorders (AUD) and tobacco use disorders (TD) frequently co-occur. The authors examined AUD-TD comorbidity over time using a state-trait (ST) model. The ST model represents variance in AUD/TD as a traitlike factor that spans measurement occasion and identifies distinct sources of variance in AUD-TD comorbidity. The ST model was evaluated on 450 young adults (baseline age = 18.5 years; 51% with family history of alcoholism) assessed 5 times over 7 years. The ST model demonstrated superior fit over a first-order autoregressive model. The tendency to diagnose with AUD and TD was partially explained by family history of alcoholism; this relationship was mediated by childhood stressors, alcohol expectancies, and behavioral undercontrol. Results supported a common third-variable influence (vs. directional) model of comorbidity. The ST model is an important conceptual and methodological approach to the prospective study of comorbidity in general.