• Attempted suicide;
  • anxiety disorders;
  • independent depression;
  • major depressive episode;
  • mood disorder;
  • substance dependence;
  • substance-induced depression


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.