Types of Circadian Rhythm Syndrome Disorders

circadian sleep disorder syndromes

Circadian rhythm sleep disorders (CRSD), also known as circadian rhythm sleep-wake disorders (CRSWD), are a group of sleep disorders characterized by irregular sleep patterns. They are caused by a chronic pattern of sleep/wake disruptions, which can be caused by a malfunction in one’s biological clock system or a mismatch between one’s endogenous oscillator and externally imposed stimuli.

As a result of this mismatch, people who suffer from circadian rhythm sleep problems tend to fall asleep at odd hours of the day. These occurrences frequently result in periodic episodes of disrupted rest, in which individuals with the illness are unable to sleep and arise at “normal” times for work, school, and other social commitments.

The four primary kinds of CRSD are delayed sleep phase disorder, advanced sleep phase disorder, non-24-hour sleep-wake disorder, and irregular sleep-wake rhythm disorder.

Based on their underlying causes, circadian rhythm sleep disorders can be divided into two categories:

  1. The first group includes intrinsic-type illnesses, which are conditions in which the endogenous oscillator has been changed
  2. Extrinsic type CRSDs are defined as disorders in which the external environment and the endogenous circadian clock are mismatched.


Persons with Delayed Sleep Phase Disorder (DSPD) have sleep-wake times that are later than normal functioning persons.

When people with DSPD try to sleep at normal sleeping times, they generally suffer very extended periods of sleep latency. Similarly, people have difficulty waking up at regular times. This is an intrinsic CRSD.


People with advanced sleep phase disorder have traits that are diametrically opposed to those with delayed sleep phase disorder.

Because these people have advanced sleep-wake timings, they go to bed and wake up significantly earlier than typical people. ASPD is less common than DSPD and is more common in older people. It is also an intrinsic CRSD.


Non-24-hour sleep–wake disorder (N24SWD) is most common in individuals that are blind and unable to detect light. It is an intrinsic CRSD defined by chronic sleep/wake cycle rhythms that are not entrained to the 24-hour light-dark environmental cycle.

As a result, people with this illness typically experience a gradual but predictable delay in sleep start and waking hours. If DSPD patients are not treated, they may acquire this disorder.


A normal 24-hour sleeping time characterizes irregular sleep-wake cycle disorder. Individuals with this disease, on the other hand, have fragmented and highly disorganized sleep, which can show as frequently waking during the night and taking naps during the day while still sleeping for a suitable amount of time.

ISWRD patients frequently report a variety of symptoms ranging from insomnia to excessive daytime sleepiness. It is also an intrinsic CRSD.


Shift work sleep disorder (SWSD) is thought to affect approximately 9% of Americans who work nights or irregular shifts. Because night shift employment directly contradicts the environmental cues that entrain our biological clock, this illness occurs when an individual’s clock is unable to adjust to the socially imposed work schedule.

Shift work sleep disorder, an extrinsic CRSD, can cause severe insomnia as well as excessive daytime sleepiness.


Circadian Rhythm Sleep Disorder is classified as a kind of sleep dyssomnia by the International Classification of Sleep Disorders. Although studies indicate that 3% of the adult population has CRSD, many people are frequently misdiagnosed with sleeplessness rather than CRSD. An estimated 10% of adults with sleep problems have a CRSD, while 16% of adolescents with sleep disorders may have a CRSD.

Patients with circadian rhythm sleep disorders often exhibit a pattern of disrupted sleep, whether it’s excessive sleep that interferes with work schedules and everyday tasks, or sleeplessness at preferred times of sleep. It should be noted that a predilection for extreme early or late wake periods is unrelated to a diagnosis of circadian rhythm sleep disorder.

There must be a clear disruption in biological cycles that impacts the individual’s desired work and daily behavior. A sleep specialist collects a history of a patient’s sleep and waking behaviors, body temperature patterns, and dim-light melatonin onset (DLMO) to make a CRSD diagnosis. This data provides information about the patient’s current schedule, as well as physiological phase markers of the patient’s biological clock.

  1. Dagan, Yaron (2002). Circadian Rhythm Sleep Disorders (CRSD) in psychiatry–a review. The Israel Journal of Psychiatry and Related Sciences. 39 (1): 19–27. ISSN 0333-7308
  2. Kim MJ, Lee JH, Duffy JF (November 2013). Circadian Rhythm Sleep Disorders. Journal of Clinical Outcomes Management. 20 (11): 513–528
  3. Zhu, Lirong; Zee, Phyllis C. (November 2012). Circadian Rhythm Sleep Disorders. Neurologic Clinics. 30 (4): 1167–1191. doi:10.1016/j.ncl.2012.08.011

Last Updated on November 16, 2023