Circadian Rhythm Disorders

Circadian rhythm sleep disorders (CRSDs) are an overall term covering a loss of synchronization between the internal biological clock and the external environment.

The person with this type of disorder experiences insomnia and/or excessive daytime sleepiness on a regular basis.  The unusual sleep pattern causes distress or maladaptation in the person’s job, family life, community activities, etc. Tests of cognitive ability show the effects of the body being out of sync with environmental cues.  Some people get depressed or hyperactive when they have these disorders.

Sleep is complex, but the current dominant (if somewhat simplistic) model of sleep need is that is results from an interaction of endogenous circadian and sleep homeostatic processes.  People with untreated or unmanaged CRSDs do not necessarily run short of sleep and their homeostatic process works as it should.  The problem results from the two cycles getting out of sync.  When the people are awake at times their bodyies want to sleep, they experience drowsiness, and when they try to sleep when their body wants to wake, they experience insomnia.  These are the characteristics of an CRSD.

Although a diagnosis of general circadian rhythm sleep is possible without further elaboration or specitivity, there are subtypes that can be characterized by the direction of the circadian shift and the source of the distress.

Types include:

Delayed Sleep Phase Syndrome. The circadian cycle is shifted several hours later in the day, so the person has trouble getting to sleep and waking up on time to meet social expectations. The behavior is common among teens, but if it persists into adulthood it can be considered a disorder. More on DSPS.

Advanced Sleep-Phase Syndrome.  This is when the cycle is shifted in the opposite direction from delayed sleep phase disorder and results in early bedtimes and early rising.  Social perceptions may lead to the notion that ASPS people are virtuous conscientious go-getters while DSPS people are lazy, but there are biological bases for these syndromes. More on ASPS.

Jet Lag. Circadian dysrhythm caused by rapid travel across time zones and finding oneself in a place with environmental cue not matching your body’s cues. Jet lag is marked by a feeling of being generally unwell, with fatigue, irritability, gastrointestinal discomfort, disorientation and, sometimes, depression. The condition is most commonly suffered by air travelers who cross more than three time zones in a single flight – hence the “jet” part. A one-time jet lag is easily recovered from in a few days, so it doesn’t officially qualify as a CRSD.  But frequent travel back and forth can put the body on edge and require intervention. "Morning larks" find it particularly difficult to adjust. Night owls generally have a better time at time. Researchers believe they have identified some of the biochemical underpinnings of jet lag. More on jet lag.

Shift Work Sleep Disorder. A disorder caused by social expectations – in this case because of their job schedules.  It’s not so bad when the worker sticks to one shift (although that shift may put him out of sync with the daylight and family expectations). The worst is when shifts rotate.  For instance, a schedule of one week on day shift, followed by one week on swing shift, followed by one week on graveyard overnight shift screws up the body.  Older workers are less able to adapt to these changes than younger ones.  As with jet lag, shift-work CRSD is more likely to strike people who are typically early risers than night owls. More on Shift Work Disorder.

Free-running Circadian Disorder.  This is when the body’s circadian rhythm drifts, apparently not entrained by zeitgebers or daylight signals.  It is like a train off the track. More on free-running disorder.

Irregular Sleep-Wake Disorder is a natural form of polyphasic sleep, where the patient sleeps for longer than a nap but shorter than a full night’s sleep.  Total sleep time is spread across the day and periods of sleep time change from one day to the next.  It is most common in the elderly. More on ISWD.


People with circadian rhythm disruptions are more apt to get metabolic syndrome and  gastrointestinal problems and other illnesses.

These disorders are often misdiagnosed and treated, mostly because doctors are unaware of them or do not consider them when evaluating patients.  The doctor must rule out sleep problems caused by other disorders or mental problems, other illnesses, and medicines (both prescribed and recreational, including coffee.) Further, to qualify as a disorder, the sleepiness and insomnia must cause the person problems functioning at work or socially.


Treatment or management is about readjusting the body’s circadian cycle so is aligns with environmental cues, or in the case of shift-work disorder, social and community expectations. This readjustment is not a one-time thing normally.  It requires continuing intervention and alignment.

Bright light treatment and melatonin help shift the circadian cycle, and in some cases hypnotic medications are employed to induce sleep. One problem for doctors is in understanding the specifics of the circadian cycle in any individual patient. While researchers can do studies which measure body temperature and melatonin levels, the typical doctor has no access to such knowledge, and must often guess when prescribing the timing of the light exposure and melatonin supplements.

Because these disorders are partially defined by and caused by social expectations, behavioral methods can be employed. The person with the disorder must make a conscious effort to adjust sleep time, and if possible arrange schedules to accommodate sleep habits.

Related Resouces

Good scientific article on circadian disorders.

See also: workaholism and sleep problems

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