Concurrent validity of the cognitive component of schizophrenia: relationship of PANSS scores to neuropsychological assessments

Abstract

Cognitive symptoms of schizophrenia may represent a separate component of the disorder that is distinct from positive or negative syndromes. In a previous study, we reported a factor analysis of the Positive and Negative Syndrome Scale (PANSS) that revealed five components, one of which we labeled the Cognitive component. In the present study, we explored the validity of the PANSS Cognitive component by examining correlations between neuropsychological measures and the five factor-analytically derived PANSS scores for 147 subjects with diagnoses of schizophrenia or schizoaffective disorder. Higher scores on the PANSS Cognitive component were significantly correlated with poorer performance on all neuropsychological tests, including the Wisconsin Card Sorting Test (WCST), the Digit Symbol Substitution Task, the Slosson Intelligence Test, and the Gorham Proverbs Test. Multiple regression revealed that these test scores explained 37% of the variance in the Cognitive component score. Neuropsychological tests have very limited associations with the other PANSS components. These results suggest that the Cognitive component of the PANSS is a valid measure of cognitive deficits in schizophrenia, and they support the hypothesis that Cognitive impairment is a distinctive feature of schizophrenia independent of positive and negative syndromes.