When acute-stage psychosis and substance use co-occur: differentiating substance-induced and primary psychotic disorders.

Substances such as alcohol, cocaine, amphetamine, and cannabis can produce psychotic reactions in individuals who are otherwise free of serious mental illness. However, persons with primary psychotic disorders, such as schizophrenia and bipolar disorder, who use these substances often present for treatment with signs and symptoms similar to those whose psychosis resulted from the use of drugs alone. While it is often difficult to distinguish substance-induced from primary psychoses, especially early in the course of treatment, this differential diagnosis has important implications for treatment planning. To help clinicians distinguish these two types of presentations, the authors first review the types of psychotic symptoms that can co-occur with substance use. They discuss the prevalence and patterns of substance use that have been found in patients with schizophrenia and other primary psychotic disorders and review the negative outcomes associated with substance use in this population. The prevalence of and types of symptoms and problems associated with psychotic symptoms that occur as a result of substance use alone are also reviewed. The authors describe assessment procedures for differentiating substance-induced and primary psychotic disorders. They stress the importance of accurately establishing the temporal relationship between the substance use and the onset and continuation of psychotic symptoms in making a differential diagnosis, as well as the importance of being familiar with the types of psychological symptoms that can occur with specific substances. The authors review the utility and limitations of a number of diagnostic instruments for assessing patients with co-occurring psychosis and substance use problems, including The Addiction Severity Index, The Michigan Alcohol Screening Test, and diagnostic interviews such as the Schedule for Affective Disorders and Schizophrenia and the Structured Clinical Interview for DSM. They then discuss the Psychiatric Research Interview for Substance and Mental Disorders (PRISM), an instrument that has been developed to address the lack of a diagnostic interview that is suitable for assessing the comorbidity of substance use and psychiatric disorders. The article concludes with a discussion of the importance of an appropriate match between diagnosis and treatment and the current state of our knowledge concerning the most appropriate types of treatment interventions for patients with substance-induced psychosis and those with dual diagnoses.