Objective: Our purpose in undertaking the present study was to explore the existence of specific areas of cognitive deficits within the context of generalized poor performance in a group of Greek patients with schizophrenia. We also sought to identify any patients who might be cognitively normal.
Method: Participants were 70 patients with schizophrenia and 42 healthy control subjects. The 2 groups were matched on age and male-female ratio but differed in their level of education. A battery of neuropsychological tests was selected to assess executive functions/abstraction, fluency, verbal and spatial working memory, verbal and nonverbal memory, attention, visuospatial ability, and psychomotor speed.
Results: Patients with schizophrenia performed more poorly than healthy control subjects, when we controlled for differences in level of education, on executive functions, working memory, verbal memory, nonverbal memory, fluency, visuospatial ability, and attention. In contrast, no significant differences were found between the 2 groups on psychomotor speed. Patients showed a more pronounced deficit on executive functions, verbal and visual memory, and visuospatial ability. Overall, 13% to 62% of the patients with schizophrenia scored within 1 SD of the mean z scores of healthy control group depending on the cognitive domains examined. In the entire sample of patients with schizophrenia, however, no individual scored within 1 SD of the mean z scores of the control group in all cognitive domains.
Conclusions: We found a generalized deficit in cognitive functioning in a group of patients with schizophrenia. We failed to find any individual patients who were healthy across all cognitive areas. The current neuropsychological profile, indicating widespread impairment, is comparable to that reported in the international literature and thus appears to be characteristic of schizophrenia. Our findings of increased difficulties with executive functions, verbal and visual memory, and visuospatial ability support previous suggestions of generalized brain dysfunction in the pathophysiology of schizophrenia.