Cognitive effectiveness of olanzapine and risperidone in first-episode psychosis.

Background: Cognitive impairment in schizophrenia-spectrum disorders is highly prevalent and notably influences functional outcomes.

Aims: To characterise the cognitive effectiveness of second-generation antipsychotic drugs.

Method: One hundred consecutive and previously unmedicated patients with first-episode schizophrenia-spectrum disorders were admitted. Seventy-seven completed baseline, 1-month and 6-month psychopathological and neuropsychological assessments. Patients were randomised to risperidone or olanzapine treatment. Four final treatment allocation groups were defined since patients continued treatment in their normal setting: risperidone, olanzapine, mixed and no-antipsychotic groups.

Results: There were no differences in cognitive effectiveness between the four treatment groups. Reliable change index methods demonstrated that nearly a half of patients showed an improvement in Global Cognitive Score at the 6-month assessment. Improvement on the neuropsychological tests ranged from 17 to 54%. A strong predictor of cognitive response was poor performance on baseline neuropsychological tests; response was moderately influenced by a low premorbid scholastic performance and IQ.

Conclusions: Cognitive improvement related to second-generation antipsychotic drugs appeared within the first 4 weeks of treatment and persisted at 6 months irrespective of treatment group. Greater cognitive dysfunction at baseline and lower premorbid cognitive background predicted cognitive improvement in our sample.