Effect of olanzapine or risperidone treatment on some cognitive functions in a one-year follow-up of schizophrenia outpatients with prominent negative symptoms

Abstract

Aims: To compare olanzapine and risperidone outcome on some neurocognitive dimensions in chronic schizophrenia patients with prominent negative symptoms.

Method: We randomised and followed for 1 year 235 chronic schizophrenia outpatients with a SANS global score > or =10 to open-label flexible-dose treatment with olanzapine or risperidone. Clinical, functional and cognitive assessments [including the COGLAB battery reaction time, vigilance-span of apprehension (VSA) and a card-sorting task] were done periodically.

Results: There were no significant differences between olanzapine (n=120) and risperidone (n=115) treatments in the neurocognitive dimensions tested. Mean+/-SD doses were 12.2+/-5.8 mg/day of olanzapine and 4.9+/-2.0 mg/day of risperidone. Patients in the olanzapine group showed a significant improvement in the VSA total score, but the within-group change was modest (effect size of 0.26); the difference with the risperidone group was not significant (p=0.207). Patients in both groups showed a significant improvement in a composite measure of executive efficiency based on the card-sorting task, with within-group effect size of 0.21 (risperidone) and 0.35 (olanzapine); the between-group difference was not significant (p=0.164). At baseline, better functional status correlated with VSA. Patients scoring lower on VSA or executive efficiency at baseline improved more on these respective measures.

Conclusion: Modest pro-cognitive effects can also be found in chronic schizophrenia outpatients with prominent negative symptoms when treated with olanzapine or risperidone.