More than 100 different disorders of sleeping and waking have been identified. They can be grouped in four main categories:

• Problems with staying and falling asleep
• Problems with staying awake
• Problems with adhering to a regular sleep schedule
• Sleep-disruptive behaviors

PROBLEMS WITH STAYING AND FALLING ASLEEP

Insomnia includes any combination of difficulty with falling asleep, staying asleep, intermittent wakefulness and early-morning awakening. Episodes may be transient, short term (lasting as long as 2 to 3 weeks), or chronic.

Common factors associated with insomnia include:

• Physical illness
• Depression
• Anxiety
• Stress
• Poor sleeping environment (e.g., noise or too much light)
• Caffeine
• Abuse of alcohol or other drugs
• Use of certain medications
• Heavy smoking
• Physical discomfort
• Daytime napping
• Counterproductive sleep habits:
  • Early bedtimes
  • Excessive time spent awake in bed

Disorders include:

• Psychophysiological insomnia (learned insomnia)
• Delayed sleep phase syndrome
• Hypnotic dependent sleep disorder
• Stimulant dependent sleep disorder

PROBLEMS WITH STAYING AWAKE

Disorders of excessive sleepiness are called hypersomnias. These include:

• Sleep apnea
• Narcolepsy
• Restless leg syndrome
• Obstructive sleep apnea
• Central sleep apnea
• Idiopathic hypersomnia
• Respiratory muscle weakness associated sleep disorder

Sleep apnea more commonly affects obese people, but it may affect anyone with a short neck or a small jaw, regardless of weight. The disorder causes breathing to stop intermittently during sleep, resulting in the person being awakened repeatedly. People with sleep apnea often they have difficulty achieving prolonged deep sleep. This results in excessive daytime sleepiness.

Narcolepsy is a condition of daytime sleep attacks as well as other features that may include sleep paralysis and hypnagogic hallucinations. Sleep attacks occur despite adequate sleep at night. A person with narcolepsy may suddenly fall asleep in any situation, without warning.

Restless leg syndrome is a condition of periodic lower-leg movements during sleep with associated insomnia or daytime sleepiness.

PROBLEMS WITH ADHERING TO A REGULAR SLEEP SCHEDULE

Problems may also occur with maintaining a consistent sleep and wake schedule as a result of disruptions of normal times of sleeping and wakefulness. This occurs when traveling between times zones and with shift workers on rotating schedules, particularly nighttime workers.

These disorders include:

• Sleep state misperception (the person actually sleeps a different amount than they think they do)
• Shift work sleep disorder
• Natural short sleeper (the person sleeps less hours than "normal" but suffers no ill effects)
• Chronic time zone change syndrome
• Irregular sleep-wake syndrome

SLEEP-DISRUPTIVE BEHAVIORS

Abnormal behaviors during sleep are called parasomnias and are fairly common in children. They include:

• Sleep terror disorder
• Sleep walking
• REM behavior disorder (a type of psychosis that develops, related to lack of REM sleep and lack of dreaming)

Sleep terror disorder is an abrupt awakening from sleep with fear, sweating, rapid heart rate, and confusion. Sleepwalking is usually not remembered by the person doing it and usually affects children 2 to 12 years old.

In adults, sleepwalking may also be caused by an organic brain syndrome, reactions to drugs, psychological disorders, and certain medical conditions.

• Awakening in the night
• Difficulty falling asleep
• Excessive daytime drowsiness
• Loud snoring
• Episodes of stopped breathing
• Sleep attacks during the day
• Daytime fatigue
• Depressed mood
• Anxiety
• Difficulty concentrating
• Apathy
• Irritability
• Loss of memory (or complaints of decreased memory)
• Lower leg movements during sleep

• Multiple sleep latency test
• Polysomnography (recording brain activity, muscle activity and breathing during sleep)

INSOMNIA

The treatment is related to the cause, if the cause can be determined. If there is an obvious physical or psychological disorder causing insomnia, it should be treated. Depression is a very common cause of insomnia and can usually be treated with medication, cognitive/behavioral therapy, or interpersonal therapy. Attempts to control environmental and lifestyle factors such as too much light, noise, caffeine or other stimulants or erratic hours of wakefulness should be made. Sleeping drugs should be used only when prescribed by a health care provider.

HYPERSOMNIA

Sleep apnea is treated with weight reduction and the administration of air under pressure through the nose. Occasionally, surgery or other measures may be needed.

Narcolepsy is treated by use of stimulating medications during the daytime. A new medication called modafanil seems to have fewer side effects than traditional stimulants; it is FDA-approved for narcolepsy and may soon be approved for shift work sleep disorder.

Restless leg syndrome is treated by treating the underlying disorder and with opiate or dopaminergic agonists.

PARASOMNIA

Night terrors are treated with hypnosis, guided imagery techniques and benzodiazepines, but safety measures may be needed to prevent people from harm during nighttime walking.

Sleep disorder clinics often are able to help people restore normal sleeping patterns through various techniques.