The effect of a single dose of 10 mg olanzapine on healthy volunteers of both sexes was examined using polysomnography and power spectral analysis. The structure and continuity of sleep were unaffected by olanzapine in both sexes. The increase in both actual sleep time and slow wave sleep in females correlated with the increase in theta power, while delta power was not significantly elevated, suggesting that theta power may be a sensitive indicator of changes in sleep. The changes in sleep had the same tendency in men, but they were not significant. The difference between the sexes could not be explained by differences in body mass index. Olanzapine affects sleep probably through 5-HT2C receptors. The receptor gene is located on the X-chromosome, inducing an allelic difference between the females and males. This difference may contribute to the different effects of olanzapine on sleep. Olanzapine seems to preserve the normal structure of sleep and increase the amount of slow-wave sleep, which might be of additional benefit in treatment of schizophrenia. The effective clinical dose may be lower for females than males.
aDepartment of Psychiatry, University of Helsinki, Lapinlahdentie, Helsinki
bFinnish Institute of Occupational Health, Topeliuksenkatu, Helsinki
cInstitute of Biomedicine, Department of Physiology, University of Helsinki, Helsinki, Finland
Correspondence to Tarja Porkka-Heiskanen, Institute of Biomedicine, Department of Physiology, University of Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland
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Received 15 March 2002 accepted 27 March 2002