Objective: To investigate the association between the Positive and Negative Syndrome Scale (PANSS) cognitive factors and cognition assessed by neuropsychological tests.
Method: Ninety patients with a psychotic illness, the majority having a schizophrenia diagnosis, were assessed with PANSS ratings and tested by a comprehensive computerized neuropsychological test battery, EuCog.
Results: Test performance was in the normal range for some of the cognitive indices, but substantially reduced for others, compared with norms, particularly speed-based indices. PANSS ratings were non-specifically associated with cognitive indices representing performance (speed and accuracy) and problem solving strategies (executive functions). There was no discriminant validity for the cognitive factor. A regression analysis suggested that the PANSS cognitive factors reflected verbal IQ but no other cognitive domain like memory, attention or speed.
Conclusion: Cognitive test performance is associated with psychopathology as assessed by PANSS items but in a non-specific way. The PANSS cognitive subscale seems to reflect over-learned verbal skills rather than the cognitive domains, which are known to be specifically affected in schizophrenia and relevant for the prognosis. Consequently, PANSS ratings cannot replace the information inherent in neuropsychological test data. The extensive speed problem of patients with schizophrenia should be studied in more detail using test batteries that focus on that problem.
Keywords: Cognition; Neuropsychology; Schizophrenia.