Independent Versus Substance-Induced Major Depressive Disorder in Substance-Dependent Patients: Observational Study of Course During Follow-Up

Objective: Clinicians frequently encounter patients presenting with both depression and substance abuse, and their diagnosis has been a source of controversy. The authors examined whether baseline and past diagnoses of DSM-IV primary (independent) or substance-induced depression or other psychiatric syndromes predict 1-year course of depression in substance-dependent patients.

Method: Inpatients with current DSM-IV major depressive disorder (MDD) and DSM-IV alcohol, cocaine, or opiate dependence (N = 110) were evaluated with the Psychiatric Research Interview for Substance and Mental Disorders (PRISM) and followed for 12 months after discharge. Logistic regression for repeated measures modeled the odds of MDD and depressed mood over time as a function of baseline diagnoses and past independent depression, controlling for demographics, substance use, and antidepressant treatment during the follow-up. Subject recruitment was conducted from July 25, 1995 to May 14, 1997.

Results: Over the 12 months, 88% of the patients experienced depressed mood for at least 1 week, and 57% experienced MDD. Depression during follow-up was equally likely among patients with current (baseline) DSM-IV independent or substance-induced MDD; in the latter group, past independent MDD increased the likelihood of MDD during the follow-up. Panic attacks, posttraumatic stress disorder (trend), borderline personality, and antisocial personality also significantly predicted depression during the follow-up.

Conclusions: In substance-dependent patients, both DSM-IV primary and substance-induced MDD predict future depression, warranting consideration for specific treatment. The data suggest the importance of a careful psychiatric history that includes attention to past episodes of independent depression as well as anxiety and cluster B personality syndromes.