Neuropsychological studies show the positive effect of treatment with atypical neuroleptics on cognitive functions in schizophrenia. The aim of this study was to assess the effect of olanzapine on prefrontal functions during 12-months of treatment in schizophrenia.

The study was performed in 48 schizophrenic patients, aged 20-48, who were treated with the generic olanzapine (Zolafren - Adamed, Poland). Psychometric evaluation was done using PANSS. Neuropsychological assessments included Wisconsin Card Sorting Test(WCST) and Trail Making Test and Stroop Color-Word Interference Test. The measurements were performed before, after 3,6 and 12 months of treatment. The daily dose of olanzapine was 5-25mg/day (mean 14.9 mg/day) after 3 month of treatment, and 5-20 mg (mean 13.6 mg/day), after 6 and 12 months of treatment.

The intensity of psychopathology on PANSS was at baseline 99 points, and after 3, 6 and 12 months of treatment 63, 54 and 51p, respectively, with significant systematic improvement during olanzapine treatment (p<0.001, ANOVA Friedman Test). After 3 month of treatment, there was a significant amelioration on TMT, Stroop, and WCST-conceptual responses. A after 3,6 and 12months of treatment significant improvements on TMT, Stroop and WCST were observed. The level of cognitive improvement was assessed with the decrease on negative symptoms. After 3 month – this correlated with improvement on TMT and WCST-perseverative errors, and after 6 and 12 months with TMT A and WCST perseverative errors.

The results obtained show a significant improvement of psychopathology and neuropsychological frontal lobe tests after long-term treatment with olanzapine.