Treatment of Schizophrenia and Comorbid Substance Abuse: Pharmacologic Approaches

Co-occurring substance use disorder is common among patients with schizophrenia, and its presence greatly worsens the course of schizophrenia. A number of theories have been introduced to explain the increased rate of substance use disorder in these patients. These theories include the notion that substance use could trigger psychotic symptoms in vulnerable individuals and the idea that the substances are used to self-medicate symptoms of schizophrenia. Our group and others have advanced a neurobiological hypothesis to explain this comorbidity—that a mesocorticolimbic brain reward circuit underlies the substance use disorder in patients with schizophrenia. Treatment of substance use disorder in these patients is best done with integrated treatment programs that combine psychosocial interventions with pharmacotherapy. Recent data suggest that the atypical antipsychotic clozapine and perhaps other atypical agents may lessen substance use in patients with schizophrenia. My colleagues and I have proposed that clozapine's effect in these patients may be related to its ability to decrease the brain reward circuit dysfunction. Research is continuing on the use of atypical antipsychotics in patients with schizophrenia and comorbid substance abuse. The adjunctive use of naltrexone or other agents also may be helpful. Further research on the optimal pharmacologic approach to patients with dual diagnosis is needed.