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

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.