BACKGROUND: Comorbid substance use and mental illness is prevalent and often results in serious consequences. However, little is known about the efficacy of treatments for patients with dual diagnosis. METHODS: This paper reviews both the psychosocial and medication treatments for those diagnosed with a substance-related disorder and one of the following disorders: (a) depression, (b) anxiety disorder, (c) schizophrenia, (d) bipolar disorder, (e) severe mental illness, and (f) nonspecific mental illness. We made no restriction of study design to include all published studies, due to the dearth of studies on treatments of patients with dual diagnosis. RESULTS: Fifty-nine studies were identified (36 randomized-controlled trials; RCT). Limited number of studies, especially RCTs, have been conducted within each comorbid category. This review did not find treatments that had been replicated and consistently showed clear advantages over comparison condition for both substance-related and other psychiatric outcomes. CONCLUSIONS: Although no treatment was identified as efficacious for both psychiatric disorders and substance-related disorder, this review finds: (1) existing efficacious treatments for reducing psychiatric symptoms also tend to work in dual-diagnosis patients, (2) existing efficacious treatments for reducing substance use also decrease substance use in dually diagnosed patients, and (3) the efficacy of integrated treatment is still unclear. This review provides a critique of the current state of the literature, identifies the directions for future research on treatment of dual-diagnosis individuals, and calls for urgent attention by researchers and funding agencies to conduct more and more methodologically rigorous research in this area.
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