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Circadian rhythm sleep disorder

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Circadian rhythm sleep disorders occur when the circadian rhythm is disrupted or is not functioning properly. They usually affect other bodily functions as well, and not just sleep.

Cause The delayed sleep phase type of circadian rhythm sleep disorder is marked by a delay of the sleep-wake cycle as it relates to the demands of society. It is often due to a psychosocial stressor (an event in a person's environment that causes stress or discomfort), especially for adolescents. The delayed sleep-wake cycle leads to chronic sleep deprivation and habitually late sleeping hours. Individuals with this type often have difficulty changing their sleeping patterns to an earlier and more socially acceptable time. Their actual sleep, once it begins, is normal. It is the timing of their sleeping and waking that is persistently delayed.

Extrinsic category

Extrinsic means something which comes from outside rather than from within a system or an organism. There are two circadian rhythm sleep disorders of the extrinsic type:

  • Jet Lag

Jet Lag often affects people who have travelled several hours east or west, through several time zones. It may take many days for the body to adjust to the new environment. The name comes from travelling by jet aircraft.

  • Shift work syndrome

Many people have problems with their sleep, appetite, alertness etc. when they work a shift during the times when their circadian rhythms indicate that they should be asleep.

Intrinsic category

Intrinsic refers to something which happens or is caused within a system or an organism. There are four circadian rhythm sleep disorders of the intrinsic type. Unless they are caused by a head injury or by a disease, they are usually genetic, that is, people are born with them. They are generally chronic; they do not go away, but they may to some degree be treated.

  • Advanced sleep-phase syndrome

Advanced sleep-phase syndrome (ASPS) is very rare. People with this syndrome are sleepy very early in the evening and they sleep from about 19:00-20:00 in the evening to about 03:00-04:00 in the early morning. Their sleep is usually normal. There are often several people in the same family who have ASPS.

  • Delayed sleep-phase syndrome

Delayed sleep-phase syndrome (DSPS) is the opposite of ASPS, and it is more common, affecting about 0.15% of adults. It usually starts in early childhood or at puberty. Some cases which start at puberty go away when the person is about 20 years old. Otherwise, the syndrome does not go away, that is, it is chronic.

People with DSPS cannot go to sleep before 03:00-06:00 in the morning, or even later. They sleep normally for 8–9 hours, but they cannot wake up in time for school or a job which starts in the morning. They can go to sleep at the same time every night and get up at the same time each day. This means that they are entrained (adjusted, synchronized) to the daily light/dark cycle. Even when they try to sleep at acceptable times, they are most alert in the late evening and the nighttime hours.

  • Non-24-hour sleep-wake syndrome

Non-24-hour sleep-wake syndrome (Non-24) is quite rare. Some people who can see have it, but it is more common among the blind. People with Non-24 sleep well for 8–9 hours, but they do not adjust to the daily light/dark cycle at all. Therefore, they go to sleep 1–2 hours later each day and wake up 1–2 hours later than the day before. This is called freerunning sleep. Their times of best alertness, appetite, body temperature rhythm and hormone cycles all move continuously around the clock, coming back to the same time after a few weeks.

  • Irregular sleep-wake disorder

Irregular sleep-wake disorder is quite rare, and it is often possible to find out what causes it, for example, a head injury, a mental handicap, dementia or some other sicknesses. People with this disorder sleep and wake several times a day, but not at the same times every day. Altogether they sleep the same number of hours as other people of the same age.


Treatment for these disorders is similar, and it often does not work very well. In addition, it can be difficult to find a doctor who knows much about circadian rhythms, as the field of study is quite new.

  • Bright light

Treatment with bright light is also called phototherapy or light therapy. People with ASPS need a lot of light in the evening and they should avoid bright light in the morning. People with DSPS need bright light as soon as they wake up and should try to avoid bright light in the evening.

  • Melatonin

Melatonin is a hormone produced in the pineal gland in the brain. It is normally only produced in the evening and at night. People with ASPS can take melatonin by mouth in the morning. People with DSPS can take melatonin in the afternoon or evening, and this treatment works also for some people with Non-24.

One can buy melatonin in the shops in the USA and Canada. In most other countries one must get it from a doctor or it might not be legal at all.

Similar treatments can be tried for the other disorders.