Neuropsychological dysfunction in schizophrenia and affective disease

We used Smith's neuropsychological test battery to study the cortical functioning of 52 patients with affective disorders, 17 schizophrenics, and 8 patients with coarse brain disease (CBD), all diagnosed according to research criteria. Testing and diagnoses were made independently and blindly. After accounting for the variance due to age, sex, handedness, educational level, and psychotropic drugs, we found that on tests of dominant hemisphere function schizophrenics performed significantly worse than patients with affective disorder but were no different from patients with CBD. On tests of nondominant hemisphere function the performance of the schizophrenics was similar to that of the other two groups, which were different from each other in that patients with CBD had poorer performance than affectives. A discriminant function analysis of the test scores applied to a jackknifed classification matrix successfully predicted research diagnosis in 86.5% of the affectively ill patients and 76.5% of the schizophrenics, for an overall hit rate of 84.1%. A canonical plot of the discriminant scores further showed distinct groups, with manics and depressives most alike but quite different from schizophrenics and patients with CBD. These findings are consistent with those derived from other neuropsychological studies, as well as EEG and CT scan studies.