The long-term treatment outcomes of depression and anxiety comorbid with substance abuse.

The impact of the comorbidity of psychiatric disorder and substance abuse on treatment outcomes was estimated using data from a longitudinal survey of 1,920 individuals who were followed nearly 15 years. Individuals with anxiety or depression symptoms at baseline generally experienced increased distress at follow-up; those who received mental health treatment experienced decreased distress at follow-up. Individuals with substance abuse/dependence symptoms who received treatment at baseline had a higher risk of follow-up disability; treated individuals with substance abuse who had comorbid anxiety and depression symptoms at baseline were at lower risk of disability at follow-up. Individuals with anxiety and depression symptoms at baseline had a higher incidence of chronic illness during follow-up; those who received treatment or had substance abuse symptoms did not. The results may improve understanding of the degree to which treatment of a primary disorder may prevent the incidence or reduce the prevalence of a secondary comorbid disorder.