Narcolepsy: sudden irresistible sleep attacks of unknown origin lasting from seconds to minutes, two to six times a day

Sleep apnea: a group of disorders characterised by cessation of breathing during sleep, lasting ten seconds or longer and occuring 30 or more times during sleep

Somnambulism: sleep walking

Insomnia: difficulty falling asleep or staying asleep

Early morning awakening is symptom of severe depression

Bruxism: teeth grinding during sleep

Night terrors: Occur in children, with periods of fright, crying, screaming, after a brief time of sleep. Usually not remembered during morning.