OBJECTIVE: Uncertainty regarding the degree to which persons with schizophrenia may lack decision-making capacity, and what the predictors of capacity may be led us to examine the relationship between psychopathology, neurocognitive functioning, and decision-making capacity in a large sample of persons with schizophrenia at entry into a clinical trial.
METHOD: In the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) schizophrenia trial, a clinical trial sponsored by the National Institute of Mental Health designed to compare the effectiveness of antipsychotic drugs, subjects were administered the MacArthur Competence Assessment Tool-Clinical Research (MacCAT-CR) and had to demonstrate adequate decision-making capacity before randomization. The MacCAT-CR, the Positive and Negative Syndrome Scale (PANSS), and an extensive neurocognitive battery were completed for 1447 study participants.
RESULTS: The neurocognitive composite score and all 5 neurocognitive subscores (verbal memory, vigilance, processing speed, reasoning, and working memory) were positive correlates of the MacCAT-CR understanding, appreciation, and reasoning scales at baseline. Higher levels of negative symptoms, but not positive symptoms, were inversely correlated with these three MacCAT-CR scales. Linear regression models of all three MacCAT-CR scales identified working memory as a predictor; negative symptoms made a small contribution to the understanding and appreciation scores.
CONCLUSIONS: Negative symptoms and aspects of neurocognitive functioning were correlated with decision-making capacity in this large sample of moderately ill subjects with schizophrenia. In multiple regression models predicting performance on the MacCAT-CR scales, working memory was the only consistent predictor of the components of decision-making capacity. Individuals with schizophrenia who have prominent cognitive dysfunction, especially memory impairment, may warrant particular attention when participating in research.