Subtypes of major depression in substance dependence.

Aims: This study evaluated features that differentiate subtypes of major depressive episode (MDE) in the context of substance dependence (SD). Design  Secondary data analysis using pooled data from family-based and case-control genetic studies of SD.

Setting: Community recruitment through academic medical centers.

Participants: A total of 1929 unrelated subjects with alcohol and/or drug dependence.

Measurements: Demographics, diagnostic criteria for psychiatric and substance use disorders and related clinical features were obtained using the Semi-Structured Assessment for Drug Dependence and Alcoholism. We compared four groups: no life-time MDE (no MDE), independent MDE only (I-MDE), substance-induced MDE only (SI-MDE) and both types of MDE.

Findings: Psychiatric measures were better predictors of MDE subtype than substance-related or socio-demographic ones. Subjects with both types of MDE reported more life-time depressive symptoms and comorbid anxiety disorders and were more likely to have attempted suicide than subjects with I-MDE or SI-MDE. Subjects with both types of MDE, like those with I-MDE, were also more likely than subjects with SI-MDE to be alcohol-dependent only than either drug-dependent only or both alcohol- and drug-dependent.

Conclusions: SD individuals with both types of MDE have greater psychiatric severity than those with I-MDE only or SI-MDE only. These and other features that distinguish among the MDE subtypes have important diagnostic and potential therapeutic implications.