Excessive sleepiness

Excessive sleepiness is not an homogeneous concept. It can manifest itself as bouts of sleepiness, irresistible and refreshing sleep episodes, abnormal lengthening of night sleep with a major difficulty waking up in the morning or at the end of a nap or even periods of a week or so of almost continuous sleep recurring at several months’ intervals. According to the recent second edition of the International Classification of Sleep Disorders (ICSD-2), disorders of excessive sleepiness are distributed within three chapters: sleep-related breathing disorders, hypersomnias of central origin not due to a circadian rhythm sleep disorder, sleep-related breathing disorders, or other cause of disturbed nocturnal sleep, and circadian rhythm sleep disorders. However in this volume aimed at psychiatrists, the presentation of disorders of excessive sleepiness will obey another logic. Following “Generalities” including epidemiology, morbidity, clinical work-up, and laboratory tests, the various aetiologies will be presented according to the following six subchapters: ♦ Hypersomnia not due to substance or known physiological condition (non-organic hypersomnia or psychiatric hypersomnia) ♦ Hypersomnia due to drug or substance ♦ Behaviourally induced insufficient sleep syndrome ♦ Hypersomnia in the context of sleep-related breathing disorders ♦ Hypersomnias of central origin ♦ And the special case of delayed sleep phase syndrome.