What is a sleep disorder?

Getting a good night's sleep is essential for feeling refreshed and alert during the day. Unfortunately, not everyone is able to get the restorative sleep they need.

According to the National Institute of Neurological Disorders and Stroke, chronic, long-term sleep disorders affect at least 40 million Americans each year. Left untreated, sleep disorders, and the resulting sleep deprivation, will likely interfere with your work, driving, and social activities and have negative effects on your physical and mental well-being.

What is a sleep disorder?

The National Institutes of Health define a sleep disorder as any difficulties related to sleeping, including:

  • difficulty falling or staying asleep,
  • falling asleep at inappropriate times,
  • excessive total sleep time, or
  • abnormal behaviors associated with sleep.

Physicians and sleep specialists typically categorize sleep disorders into four main categories specified by the International Classification of Sleep Disorders. These include:

  • dyssomnias,
  • parasomnias,
  • medical/psychiatric disorders, and
  • proposed sleep disorders.


Dyssomnias are disturbances in the amount, timing, or quality of sleep resulting in excessive daytime sleepiness or insomnia. The International Classification of Sleep Disorders lists three subcategories of dyssomnias:

  • Intrinsic sleep disorders originate inside the body and are due to a variety of possible causes. Common intrinsic sleep disorders include: psychophysiologic insomnia, idiopathic insomnia, narcolepsy, obstructive sleep apnea, central sleep apnea, restless legs syndrome, and periodic limb movements in sleep
  • Extrinsic sleep disorders originate outside the body and are due most commonly to behavioral or environmental factors . Common extrinsic sleep disorders include: inadequate sleep hygiene, environmental sleep disorder, insufficient sleep syndrome, stimulant-dependent sleep disorder, alcohol-dependent sleep disorder, and hypnotic-dependent sleep disorder.
  • Circadian rhythm sleep disorders describe the disruption of the sleep cycle in a 24-hour period. Common circadian rhythm sleep disorders include: jet lag, shift-work sleep disorder, irregular sleep-wake pattern, delayed sleep phase syndrome, and advanced sleep phase syndrome.


Parasomnias are disorders of partial arousal or disorders that interfere with sleep stage transitions. Abnormal events occur during sleep. The International Classification of Sleep Disorders lists four subcategories of dyssomnias:

  • Arousal disorders are disorders of partial arousal. Common arousal disorders include: confusional arousals, sleepwalking, and sleep terrors.
  • Sleep-wake transition disorders are disorders that interfere with sleep stage transitions. Common examples include: rhythmic movement disorder, sleep starts, sleeptalking, and nocturnal leg cramps.
  • Other parasomnias include common sleep disorders such as sleep bruxism (teeth grinding), sleep enuresis (bedwetting), primary snoring, infant sleep apnea, and sudden infant death syndrome (SIDS).
  • Parasomnias usually associated with rapid eye movement (REM) sleep occur during the REM sleep stage. Common examples include: nightmares, sleep paralysis, and REM sleep behavior disorder.

Medical/psychiatric sleep disorders

Sleep disorders are often attributed to medical or psychiatric disorders. The International Classification of Sleep Disorders lists three subcategories of medical/psychiatric sleep disorders:

  • Sleep disorders associated with medical disorders. Common examples include: alcoholism, chronic obstructive pulmonary disease, asthma, sleep-related gastroesophageal reflux, peptic ulcer, and fibrositis syndrome.
  • Sleep disorders associated with neurological disorders. Common examples include: degenerative brain disorders, dementia, sleep-related epilepsy, and sleep-related headaches.
  • Sleep disorders associated with psychiatric disorders. Psychoses, anxiety, depression, and panic disorders can result in excessive sleepiness, insomnia, or other disruptions in the sleep cycle.

Proposed sleep disorders

Proposed sleep disorders encompass sleep problems for which there is not enough information available to positively establish them as distinct disorders. Examples in this category include:

  • short sleepers (someone who regularly sleeps less than 75% of the sleep time typically required for his or her age group but feels no negative effects from this shortened sleep),
  • long sleepers (someone who regularly sleeps more than 10 hours a night),
  • subwakefulness syndrome (lack of daytime alertness with no apparent sleep disruption),
  • fragmentary myoclonus (brief, involuntary jerks or twitches), sleep hyperhydrosis (night sweats),
  • menstrual-associated sleep disorder,
  • pregnancy-associated sleep disorder,
  • terrifying hypnagogic hallucinations,
  • sleep-related laryngospasm , and
  • sleep choking syndrome.