Relationship of good and poor Wisconsin Card Sorting Test performance to illness duration in schizophrenia: a cross-sectional analysis

The authors investigated whether schizophrenic patients with good and poor performance on the Wisconsin Card Sorting Test (WCST) showed cognitive modifications related to duration of illness. Of the 154 patients evaluated with the WCST, 56 subjects had normal or mildly impaired performance and 98 showed impairment on the basis of the number of categories achieved (0-3 categories = poor performance). These subsamples were then cross-sectionally divided into three subsamples depending on length of illness (< 5 years, 6-10 years, > 10 years). The inclusion of 69 healthy controls allowed the effect of age to be taken into account. The schizophrenic group as a whole and the group of poor performers did not show differences in any of the WCST indices related to length of illness. Good performers instead showed improvement on the intermediate length-of-illness group (6-10 years of illness), and then decline in the third one (> 10 years). Good performers only showed a positive significant correlation between age, age at onset, educational level and successful WCST performance. Results for the poor performers support the hypothesis of no progressive 'deteriorating' course of schizophrenia, while good performers show an unstable pattern of cognitive functions. These data support the hypothesis that cognitive deficits associated with schizophrenia cannot be considered a unitary trait, but emerge along different hypothetical trajectories.