The most common sleep disorders include difficulty falling asleep or staying asleep (insomnia) and snoring. Other less common sleep disorders include:

• Sleep apnea, in which a person regularly stops breathing during sleep for 10 seconds or longer (apneic episodes). Sleep apnea usually is caused by blockage (obstruction) in the nose or mouth (upper airway). The blockage may be caused by defects of the nose, larger-than-average soft tissues in the throat, or enlarged tonsils and adenoids.
• Abnormal decrease in the depth and rate of breathing (hypopnea).
• Narcolepsy, which causes sudden sleep attacks and may occur during any type of activity at any time of day.
• Parasomnias, which cause undesirable physical activities during sleep involving physical activity, nervous system changes (such as breathing, heart rate, blood pressure, and sweating), or both. While “asleep,” a person with parasomnia may walk, scream, rearrange furniture, eat odd foods, or wield a weapon.
• Restless legs syndrome (nocturnal myoclonus), a condition that produces an intense, uncomfortable, and often irresistible urge to move the legs.