Hypersomnolence disorders

**Definition:** Hypersomnolence disorders are characterised by a complaint of daytime sleepiness that is not due to another sleep-wake disorder (e.g. disturbed nocturnal sleep, misaligned circadian rhythm, or breathing disorder). Individuals with excessive sleepiness may show irritability, concentration and attention deficits, reduced vigilance, distractibility, reduced motivation, anergia, dysphoria, fatigue, restlessness, and lack of coordination.