Dual diagnosis

Dual diagnosis denotes the co-occurrence of severe mental illness and substance use disorder. This contribution summarizes the literature on dual diagnosis by reviewing epidemiology, phenomenology, clinical correlates, assessment, treatment and current research. Epidemiological data from several countries show that substance abuse or dependence is common (approximately 50%) among persons disabled by severe mental disorders such as schizophrenia, bipolar disorder or chronic depression. These individuals use the same drugs as others in their communities but are considerably more likely to experience the adverse consequences that define a disorder. In this population, even relatively small amounts of psychoactive substances are associated with a range of negative outcomes, such as increased rates of relapse, hospitalization, violence, incarceration, homelessness and serious blood-borne infections. All patients with severe mental illnesses should be screened for substance abuse, and those with a confirmed diagnosis should receive thorough assessment and treatment. Current treatments involve a variety of techniques for combining and tailoring mental health and substance abuse interventions within one treatment setting; together these interventions are termed ‘integrated treatment’. The current intervention research supports integrated treatment in general, and specific interventions that consistently lead to stable remissions of substance use disorders, such as dual diagnosis groups, residential dual diagnosis programmes and contingency management.