A preliminary study of the comparative effects of olanzapine and risperidone on cognition in schizophrenia.

The aim of this study was to compare the effects of olanzapine and risperidone on cognitive functions in patients with schizophrenia. The subjects were schizophrenic outpatients, all meeting DSM-IV diagnostic criteria for schizophrenia and already treated with risperidone. In the experimental group (15), risperidone was changed to olanzapine to be administered for 8 weeks. Risperidone was maintained without a change in the daily dose in the control group (13). The assessment of clinical symptoms and cognitive functions in both groups was made at baseline and at 8 weeks. The experimental group relative to the control group showed significant improvement in five items such as immediate and delayed recall of verbal memory, verbal fluency, visual memory and total error of executive function. Although these data are preliminary, they could suggest the possibility of cognitive benefits from treatment with olanzapine relative to risperidone. These findings did not appear to be mediated by changes in clinical symptoms and side effects. Copyright 2004 John Wiley & Sons, Ltd.