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This study has used neuropsychological tasks--Wisconsin Card Sort (WCST), Trail Making (TMT) A and B, Verbal Fluency, Digit Span--to compare acute and currently off-medication schizophrenics, patients with unipolar nonpsychotic major depression and healthy controls. Both patient groups differed significantly from healthy controls in their neuropsychological performance. Furthermore there was only little (quantitative) difference between schizophrenics and depressed patients in the frontal lobe associated tasks: WCST, TMT and Verbal Fluency. Depressed patients tended to perform worse than schizophrenics on Digit Span, a task hypothesized to involve other than frontal areas of the brain. Although the group of depressed patients was older than the schizophrenic sample, the effect of age may not totally explain the findings. The results indicate that there do exist disturbances in frontal lobe cognitive functioning in schizophrenia and depression. Symptomatology (SANS/SAPS) and cognitive functioning in the schizophrenic group revealed only a trend for negative symptoms to be associated with worse performance in the WCST, but were significantly correlated with negative as well as positive symptoms on the TMT.
Franke et al. (Tue,) studied this question.