Relationship of individual cognitive abilities to specific components of decisional capacity among middle-aged and older patients with schizophrenia.

Prior empirical studies suggest that cognitive impairment is the strongest predictor of capacity to consent to research among persons with schizophrenia. Yet, despite the frequency and importance of cognitive deficits and impaired decisional capacity in schizophrenia, the scope of neuropsychological testing in most published reports in this area has been relatively narrow. In the present study of 70 people with schizophrenia aged 40 to 70 years we evaluated decisional capacity with the MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR). Participants were also evaluated with standardized rating scales of psychopathology and level of insight and with a comprehensive neuropsychological test battery that permitted evaluation of 7 specific cognitive abilities. Results showed that the strongest correlates of capacity (particularly, understanding and appreciation of disclosed information) were cognitive test scores, but there was little evidence of differential relationships between individual cognitive abilities and specific dimensions of capacity. Understanding was also correlated with severity of negative symptoms and of general psychopathology, but not with age, education, severity of positive or depressive symptoms, or level of insight. Understanding improved over successive presentations of consent-relevant information. The results suggest that age and diagnosis should not be viewed as determinants of decisional capacity; investigators should be alert to the presence of cognitive deficits, as well as negative symptoms. Also, an interactive dialogue between patient and investigator with repeated presentation of information is likely to aid understanding of disclosed information among patients with schizophrenia.