Excessive daytime sleepiness in psychiatric disorders: Prevalence, correlates and clinical significance.

This study examined the prevalence of excessive daytime sleepiness, as measured by the Epworth Sleepiness Scale (ESS), in a cohort of adult psychiatric patients. A total of 300 psychiatric outpatients and an additional 300 healthy controls completed the ESS. Excessive sleepiness was defined by a score of > or =10. The prevalence of excessive daytime sleepiness was higher in the psychiatric group (34%) than the control group (27%), and the mean ESS score was also significantly higher in the psychiatric group. The prevalence of excessive sleepiness was higher for female psychiatric patients, but this pattern was not found in the control group. Surprisingly, there was no difference in ESS score between patients taking antipsychotic medication and those not taking antipsychotic medication. The data suggest that excessive daytime sleepiness is a significant issue in general adult psychiatry, but this must be interpreted against a relatively high prevalence in the normal population.