The effect of treatment with risperidone,olanzapine or phenothiazines on cognitive functions in patients with schizophrenia

INTRODUCTION: Theaimofthestudywastocomparetheeffectsofrisperidone, olanzapine and phenothiazines on cognitive functions in schizophrenia during short-term (4 - 6 weeks) and long-term (3 - 4 months) treatment. METHOD: Seventy patients with schizophrenia were investigated: 30 treated with risperidone, 20 with olanzapine and 20 with phenothiazines, in standard doses. Psychometric measurements were made with the Positive and Negative Syndrome Scale (PANSS), and neuropsychological tests included the Trail Making Test (TMT), the Stroop Test and the Wisconsin Card Sorting Test (WCST). RESULTS: PANSS negative symptoms decreased significantly after risperidone and olanzapine, did not change after short-term, and improved marginally after long-term, phenothiazine treatment. Risperidone treatment resulted in significant amelioration of performance on all neuropsychological tests after both short- and long-term treatment. Olanzapine gave benefit on five out of seven subtests, although in most instances this effect was noted only after long-term treatment. Olanzapine was inferior to risperidone in improving WCST performance. Treatment with phenothiazines brought about improvement on two subtests while the results on three showed significant deterioration. CONCLUSION: The results obtained suggest that novel antipsychotics show differential effect on cognition, with risperidone especially improving working memory; however, their effect on negative symptoms and cognitive functions is better than that of typical neuroleptics.