Higher motor activity in schizophrenia patients treated with olanzapine versus risperidone

There are indications that atypical antipsychotics differ in the probability of causing motor retardation. Whereas olanzapine seems to exert sedation, risperidone might slow patients because of parkinsonism or increased negative symptoms. Objective data on gross motor activity are not available. We present actigraphic data of 16 schizophrenia patients treated with olanzapine (mean dose, 21.1 mg/d) and 23 with risperidone (mean dose, 4.7 mg/d) to investigate possible differences in their effects on motor activity. Participants wore actigraphs continuously for 24 hours at the nondominant arm. Groups did not differ in age, Positive and Negative Syndrome Scale scores, duration of illness, and number of episodes. Patients treated with olanzapine had higher activity levels than those treated with risperidone (P = 0.024); this effect was robust and also present after covarying for chlorpromazine equivalents and Positive and Negative Syndrome Scale scores. Movement index (proportion of active episodes) and the average duration of immobility, however, failed to show any difference between groups. The results indicate that patients on olanzapine are more active during the day than patients on risperidone. It remains unclear whether this difference is due to subthreshold parkinsonism with risperidone or stronger beneficial effects of olanzapine on psychomotor slowing. Because the average duration of immobility remained unaffected, sedation is not likely to be the cause for the observed differences.