Cognitive deficits in schizophrenia and affective disorders: evidence for a final common pathway disorder

This study was designed to determine whether patients with schizophrenia and those with affective disorders display a common pattern of cognitive deficits. Cognitive performance was assessed with a neuropsychological test battery in consecutively admitted in-patients with schizophrenia (n= 100) and affective disorders (n= 100). The two groups of patients showed a similar pattern of cognitive deficits, especially in tests focusing on attentional capacities. The groups only differed significantly in their performance on the Wisconsin Card Sorting Test (WCST), with the schizophrenic patients performing less well. These results suggest that, with the exception of the deficit as measured by the WCST, similar cognitive impairments exist in schizophrenia and affective disorders, even at very early stages of the illness. Therefore, patients with schizophrenia and those with affective disorders cannot be qualitatively distinguished with sufficient reliability. We postulate that the cognitive deficit pattern represents a final common pathway disorder in the two groups of patients.