Associations between substance use, neuropsychological functioning and treatment response in psychosis

Relationships between substance use, severity of psychosis, and neuropsychological functioning were examined, together with their associations with treatment response and retention status. Participants included 477 people with psychosis (354 volunteers registered on a research database, and 123 enrolled in a treatment trial for substance misuse). Variables of primary interest included substance use history, course of psychotic disorder, and neuropsychological functioning on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Specific RBANS deficits were associated with a more chronic illness course. Compared to those with a stable or chronic course, younger people with a single episode of psychosis were more likely to have uncertain diagnoses, higher levels of substance use problems and variable neuropsychological functioning. History of substance use was not associated with additional overall neuropsychological deficits. Likewise, treatment retention and outcome were not associated with neuropsychological functioning. The findings suggest that, among people with co-existing psychotic and substance use disorders, response to cognitive-behaviour therapy is likely to be independent of neuropsychological functioning. Consideration should also be given to the potential use of neuropsychological assessments to assist differentiation of likely substance-associated psychosis from primary psychosis.