Hypersomnia in bipolar depression: a comparison with narcolepsy using the multiple sleep latency test

Hypersomnia (excessive sleeping) is not characteristic of affective disorders such as depression, except in younger depressed patients, particularly those in the depressed phase of bipolar depression. There is little information available about this phenomenon, but one speculation is that hypersomnia is related to narcolepsy, a sleep disorder characterized by attacks of drowsiness and sleep. In narcolepsy, it has been found that patients spend an unusually large amount of time in the REM stage of sleep. In at least one study of patients with bipolar depression, who were not in an active disease phase, a high percentage of the time sleeping was spent in the REM stage as well. In the present study, 25 patients with bipolar depression, who were currently in a depressed phase, reported symptoms of hypersomnia. The patients were studied for two nights in a sleep laboratory. On each night, sleep characteristics were recorded and data were collected on daytime naps. When data were compared to that collected for 23 patients with narcolepsy who were not depressed, no similarities were found in the sleep characteristics of the two groups. It is concluded that hypersomnia in depressed patients is likely to be due to lack of interest, withdrawal, decreased energy, and other symptoms characteristic of depression, rather than to an increase in the patients' need to sleep or to an increase in REM-stage sleep. (Consumer Summary produced by Reliance Medical Information, Inc.)