The comorbidity of major depression and substance use disorder (SUD), which includes both alcohol and drugs, remains very common in medical and psychiatric settings (Fig. 19-1).1–3 Both major depression and SUD are among of the most common psychiatric disorders, each leading to significant morbidity and mortality and placing a heavy burden on the health care system.4 In clinical settings, however, SUDs are often underdiagnosed or missed entirely. Even if the SUD is correctly identified, treatment is often inadequate or not offered at all.5,6 Studies have consistently noted that patients with both depression and SUD present with worse symptoms and have poorer outcomes, including a higher incidence of suicide attempts, than patients with either disorder alone (Fig. 19-2).7,8 Research on the dually diagnosed population is still in its early stages, and significant gaps still remain.9 Research on the comorbidity between dual diagnosis and medical illness is even less frequently studied. Nevertheless, when approaching a depressed patient with comorbid SUD, clinicians need to be aware of the specific issues unique to this population.
Prevalence of comorbid mood and anxiety disorders in the general population with SUD. (Data from Grant BF, Dawson DA, Stinson FS, et al: The 12-month prevalence and trends in DSM-IV alcohol abuse and dependence: United States, 1991–1992 and 2001–2002, Drug Alcohol Depend 2004;74(3):223–234.).
Suicide attempts in depressed patients with and without comorbid SUD. (Data from Davis LL, Rush JA, Wisniewski SR, et al: Substance use disorder comorbidity in major depressive disorder: an exploratory analysis of the Sequenced Treatment Alternatives to Relieve Depression cohort, Compr Psychiatry 2005;46(2):81–89.)
The comorbidity between SUD and psychiatric disorders has been documented in all major epidemiological studies conducted to date. The Epidemiological Catchment Area (ECA) study reported a lifetime prevalence of 5.9% for major depression and 16.7% for any SUD in the general population.3 Individuals with a diagnosis of major depression or other affective disorders showed elevated rates for SUD—16.5% for alcohol use disorder and 18% for drug use disorder. Conversely, individuals with any SUD were 1.9 times and 4.7 times more likely to have a diagnosis of depression or other affective disorders, respectively.
The National Epidemiological Survey of Alcohol and Related Conditions study (NESARC)10 utilized face-to-face surveys with a broad sample of noninstitutionalized US citizens. It provided significant advantages over prior surveys by using the DSM criteria, differentiating primary mood disorders from substance-induced mood disorders, and including both substance abuse and dependence. Overall, 9.4% of the US population met DSM-IV criteria for any SUD within the past year. Among respondents meeting criteria for any SUD in the past year, 19.7% also met criteria ...