Changes in neuropsychological functioning following treatment with risperidone, olanzapine, and conventional antipsychotic medications.

Objective: To compare changes in neuropsychological functioning over time among adults with schizophrenia treated with atypical and conventional antipsychotics, controlling for phenomenological changes, medication dosage, concomitant use of anticholinergic medications, and practice effects.

Methods: In a larger clinical trial, 108 patients diagnosed with schizophrenia or schizoaffective disorder were randomly assigned to medication groups (risperidone, olanzapine, or conventional medications), treated in an open-label design, and monitored prospectively for 12 months using standard neuropsychological and symptomatology instruments.

Results: Significant differential effects were evident on the ability to maintain and rapidly shift mental set within a psychomotor task, with patients in the conventional medication group consistently making more errors over time until the 12-month follow-up, when the olanzapine group made significantly more errors. Significant differential effects were also evident on delayed memory, with patients receiving olanzapine improving more steadily over time until the 12-month follow-up, when patients in the conventional group were able to recall significantly more. Positive and negative symptomatology was a significant, inversely related covariate on most of the cognitive measures examined.

Conclusions: The atypical and conventional medications examined were not consistently differential enhancers of cognitive functioning on disparate cognitive functioning measures over time.