Independent versus substance-induced major depressive disorders in first-admission patients with substance use disorders: An exploratory study

BackgroundClinical differences between independent and substance-induced (S-I) major depressive disorders (MDDs) in patients with substance use disorders (SUDs) are insufficiently studied.MethodsThe catchment area sample consisted of 42 SUD patients with independent and/or S-I MDD (bipolar disorders excluded), admitted consecutively to addiction clinics or psychiatry departments (inpatient or outpatient) with no previous treatment history from specialized services. Assessments included the Psychiatric Research Interview for Substance and Mental Disorders (PRISM), the Structured Clinical Interview for DSM-IV, Axis II, Personality Disorders (SCID-II), the Inventory of Depressive Symptoms (IDS), the Montgomery–Asberg Depression Rating Scale (MADRS), and the Symptom Check List, 90 questions, revised (SCL-90-R).ResultsOf the 42 SUD patients, 48% had independent MDD episode(s) only, 24% had S-I MDD episode(s) only, and 28% had both independent and S-I MDD episodes. Insomnia, psychomotor agitation, concentration and decision problems, melancholic features, higher total MDD symptom count, longer time being depressed, higher mean score on the Montgomery–Asberg Depression Rating Scale, and shorter duration of SUDs characterized independent MDDs.LimitationsSmall sample size with risk of type II error.ConclusionsIndependent MDDs were more severe and had different qualities compared with S-I MDDs, suggesting important treatment implications. Longitudinal studies including larger samples and carefully addressing the association between SUD subtypes and MDD subtypes are needed to substantiate our findings.