Delayed sleep-phase syndrome

Delayed sleep-phase syndrome (DSPS) is a chronic disorder of sleep timing in which sufferers fall asleep later than most people and wake up later. There is not necessarily any problem with insufficient or unrefreshing sleep.  The main problematic characteristic of this syndrome is that the person with it is out of sync with the rest of society and this can pose problems in his or her family life, work life, school, etc.

People with DSPS tend to fall asleep at very late times, and also have difficulty waking up in time for normal work, school, or social needs. DSPS is treatable, but cannot be cured. It is often mistaken for insomnia, and treated inappropriately.

The shift in sleep time isn’t just a preference.  Tests show people with this condition has physiological markers (body temperature, melatonin level) that indicate a later sleep period than normal people.

DSPS is responsible for 7 -10% of cases of putative chronic insomnia in adults that show up at sleep clinics. The true number may be higher because of underdiagnosis.

Even young, pre-adolescent kids display a chronotype with some tending to the night owl type.  In adolescence most kids experience a forward shift in the circadian cycle; it is common for teens to sleep late and stay up late.  It is so common that it is almost normal for teens to have what would be classified as DSPS in adults.  By the time they reach their mid 20s, people tend to return to their natural chronotype with most rising and retiring at what are considered socially normal hours.  Some individuals, however, continue to live the teen pattern of late rising and late falling asleep.  These people are not immature or lazy or refusing to grow up (although they get such accusations).  They have DSPS.

There is a process called the Dim Light Melatonin Onset (DLMO) Test that can be used in diagnosing DSPS but few practitioners use it. While doctors may be quick to call the patient complaints as simple insomnia, a more detailed description of the patient’s sleep history and behavior, and an awareness of DSPS by doctors, can lead to an accurate diagnosis.

It is hard to say how many people have DSPS. Published studies have used small sample sizes. A Norwegian study found the disorder affects less than 0.2% of adults, but other sources point to it being more common. Another study estimates 10% of those with apparent chronic insomnia actually have DSPS. DSPS is equally distributed among both sexes and is not linked to any familial patterns. DSPS usually begins after a change in the normal sleeping pattern. Patients usually report that they had previously stayed up nights; for example studying or taking night shifts.

Lazy Bones

People with DSPS are sometimes viewed as lazy and lacking in ambition or drive. It is, of course, unfair to characterize them as such, but study of the personality of those with DSPS shows why this stereotype may be enforced by other issues. A personality study of young adults with DSPS shows they tend to score lower on the personality metric Conscientiousness than the general population. They also tend to be more neurotic and introverted.


The body’s overall circadian rhythm is controlled by the suprachiasmatic nuclei (SCN) in the brain. Most of the time, the circadian rhythm follows the 24-hour day-night schedule, as the body keeps on track with environmental cues. People with DSPS may not respond to environmental zeitgeibers that way other people do. Scientists are not sure, but there is some thought that people with this disorder are overly sensitive to light during the evening, leading to a delay in bedtime.  This response to light is sometimes called the light phase response curve.  This could be due to a lesion to the SCN, other neurological diseases, environmental changes, frequent travels or shift work. Other scientists hypothesize that people with DSPS do not respond to sleep debt by sleeping more the way others do, which changes their homeostatic drive for sleep.

Depression is often co-morbid with DSPS.  The symptoms of depression include insomnia (in most patients) and hypersomnia (in a minority), and DSPS can be confused for both insomnia and hypersomnia.


DSPS patients are frequently mind-boggled with trying to find a way to fall asleep at a socially acceptable time. They often try several tactics to adjust including trying to go to sleep early, setting several alarm clocks to go off in the morning, getting others to wake them in the morning and the use of sleeping pills. Formal tracking through a polysomnogram, home monitoring device, or sleep diary shows such signs as: falling asleep after 2 am, plenty of sleep after sleep onset, waking up late during the day, and oversleeping on the weekends. Patients with DSPS are classic "night owls" and say they are at their optimal performance at night.

In about half of adult patients, psychiatric problems may be present to some extent. Adolescents suffering from DSPS who fail to cooperate in resetting their sleep schedules may have clinical depression. The severity of DSPS is classified mild, moderate or severe based on the number of hours it takes to fall asleep and its impact on social or occupational functioning.  Patients show up at the doctor’s office after absenteeism from school or work and are often considered by their families to be lazy and lack motivation.


DSPS treatments attempt to adjust the person’s circadian rhythm to fit the sleep pattern into a schedule that can allow the person to meet the demands of a desired lifestyle. Good sleep hygiene is the first thing to get in order, as it is for pretty much every sleep problem. According to the American Academy of Sleep Medicine, the word chronotherapy was invented to describe methods to help DSPS sufferers.

Methods that can be used

Treatment is meant to allow the person with DSPS to wake up at a given time feeling refreshed and functional.

Actigraphy and DSPS


"Dawn is when men of reason go to bed" - Ambrose Bierce - The Devil's Dictionary.

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