A sleep disorder (somnipathy) is a medical disorder of the sleep patterns of a person or animal. Some sleep disorders are serious enough to interfere with normal physical, mental and emotional functioning. A test commonly ordered for some sleep disorders is the polysomnography

Disruptions in sleep can be caused by a variety of issues, from teeth grinding (bruxism) to night terrors. When a person suffers from difficulty in sleeping with no obvious cause, it is referred to as insomnia. In addition, sleep disorders may also cause sufferers to sleep excessively, a condition known as hypersomnia. Management of sleep disturbances that are secondary to mental, medical, or substance abuse disorders should focus on the underlying conditions.

Common Sleep Disorders

• Primary insomnia:
  Chronic difficulty in falling asleep and/or maintaining sleep when no other cause is found for these symptoms
• Bruxism:
  Involuntarily grinding or clenching of the teeth while sleeping
• Delayed sleep phase syndrome (DSPS):
  Inability to awaken and fall asleep at socially acceptable times but no problem with sleep maintenance, a disorder of circadian rhythms Other such disorders are advanced sleep phase syndrome (ASPS), non-24-hour sleep-wake syndrome (Non-24), and irregular sleep wake rhythm; all much less common than DSPS, as well as the transient jet lag and shift work sleep disorder
• Hypopnea syndrome:
  Abnormally shallow breathing or slow respiratory rate while sleeping
• Narcolepsy:
  Excessive daytime sleepiness (EDS) often culminating in falling asleep spontaneously but unwillingly at inappropriate times
• Cataplexy:
  A sudden weakness in the motor muscles that can result in collapse to the floor
• Night terror:
  Pavor nocturnus, sleep terror disorder: abrupt awakening from sleep with behavior consistent with terror
• Parasomnias:
  Disruptive sleep-related events involving inappropriate actions during sleep; sleep walking and night-terrors are examples
• Periodic limb movement disorder (PLMD):
  Sudden involuntary movement of arms and/or legs during sleep; for example kicking the legs, also known as nocturnal myoclonus
• Rapid eye movement behavior disorder (RBD):
  Acting out violent or dramatic dreams while in REM sleep (REM sleep disorder or RSD)
• Restless legs syndrome (RLS):
  An irresistible urge to move legs; RLS sufferers often also have PLMD
• Situational circadian rhythm sleep disorders:
  Shift work sleep disorder (SWSD) and jet lag
• Sleep Apnea, and mostly Obstructive sleep apnea:
  Obstruction of the airway during sleep, causing lack of sufficient deep sleep; often accompanied by snoring
• Sleep paralysis:
  Characterized by temporary paralysis of the body shortly before or after sleep; accompanied by visual, auditory or tactile hallucinations - not a disorder unless severe, often seen as part of narcolepsy
• Sleepwalking or somnambulism:
  Engaging in activities that are normally associated with wakefulness (such as eating or dressing), which may include walking, without the conscious knowledge of the subject
• Nocturia:
  Frequent need to get up and go to the bathroom to urinate at night. It differs from Enuresis, or bed-wetting, in which the person does not arouse from sleep, but the bladder nevertheless empties
• Somniphobia:
  Dread of sleep