ABSTRACT
The common co-occurrence of psychiatric disorders with alcohol and drug use disorders is well recognized. The reasons for co-occurrence, the best methods to differentiate substance abuse from psychiatric syndromes, and the best treatments for comorbidity remain open research questions. Nevertheless, a consensus is emerging that comorbid psychiatric and substance use disorders present problems and complications that do not occur when the clinical picture is limited to a single disorder. The present chapter describes the prevalence and natural history of the co-occurrence of substance use disorders and psychiatric disorders, and directions for future research in this area.
