Idiopathic hypersomnolence is excessive sleeping (hypersomnia) without an obvious cause. It is different from narcolepsy in that idiopathic hypersomnia does not involve suddenly falling asleep or losing muscle control associated with strong emotions (cataplexy). Symptoms often develop slowly during adolescence or young adulthood and may include daytime naps that do not relieve drowsiness, difficulty waking from a long sleep, increased need for sleep during the day, and increased sleep time (up to 14 - 18 hours per day). Other symptoms may include anxiety, feeling irritated, low energy, restlessness, slow thinking or speech, loss of appetite, and memory difficulty. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.