Circadian Rhythm Sleep Disorders (CRSD)

By Sheryl Grassie

Jul 1st, 2022

By clicking on the product links in this article, Mattress Advisor may receive a commission fee at no cost to you, the reader. Read full disclosure statement.

Expert Insights from Dr. Brooke Dulka, a medical writer and neuroscientist who received her Ph.D. in biological psychology from the University of Tennessee, and she is currently a postdoctoral researcher at the University of Wisconsin-Milwaukee where she studies the neurobiology of memory.

Circadian rhythm is our internal 24-hour clock. It cycles around in predictable patterns every day telling us when to sleep, when to wake up, when to eat, and so on. This master clock is operated by a group of neurons in the brain called the suprachiasmatic nucleus which takes cues our body sends when it senses changes in the environment.

For example, when we see the sun setting and night fall, sensors in our eyes send a message to the suprachiasmatic nucleus which triggers the production of melatonin, the hormone that makes us sleepy.  

For most people, this process works like, well, clockwork. But some people’s internal clocks fall out of rhythm, and their sleep-wake cycle is disrupted. This can result in a circadian rhythm sleep disorder.

What are Circadian Rhythm Sleep Disorders?

Circadian rhythm sleep disorders (CRSD) are a family of related sleep disorders, all characterized by an inability to sleep and/or wake at appropriate times due to the dictates of the individual’s biological or circadian clock.  

People with a circadian rhythm sleep disorder attempt to sleep (or usually fall asleep) at an abnormal time in their circadian cycle. It’s like having jet lag all the time. Usually, the sleep is of normal quality, and even its quantity would be usually sufficient if the person were allowed to start and finish their sleep at the times dictated by their body clocks. But often this does not fit in with the schedule for normal work, school, or social needs. 

Types of Circadian Rhythm Sleep Disorders

There are several types of circadian rhythm sleep disorders, including: 

  • Delayed Sleep Phase Disorder (DSP)
  • Advanced Sleep Phase Disorder (ASP)
  • Non-24-Hour Sleep-Wake Disorder (non-24)
  • Irregular Sleep-Wake Rhythm Disorder (ISWRD)
  • Jet Lag Disorder
  • Shift Work Sleep Disorder

Delayed Sleep Phase Disorder (DSP)

This type of circadian rhythm sleep disorder is the most common. It occurs when someone goes to sleep but wakes later — more than two hours later than what is considered normal. People with DSP tend to be “night owls,” sometimes staying awake until 1 a.m. or later and waking up in the late morning or early afternoon.

This condition is more common in adolescents and young adults. There is some debate whether DSP is actually a sleep disorder among teens or if it’s just a normal — but unexplained — phase of the circadian rhythm development.

Symptoms of DSP

Delayed sleep phase disorder is hallmarked by feeling most alert in the evening and an inability to fall asleep at the desired time. Individuals with this disorder have an overall sleeping and waking schedule that is pushed back by at least two hours. They generally go to bed between 1-4 AM. and wake between 8-11 AM. The inability to fall asleep is considered a form of insomnia, but when coupled with an inability to wake up it is considered a sleep disorder. For people with delayed sleep phase disorder, the challenge with sleep is on both ends and the entire schedule is pushed back.

There are generally no other sleep problems associated with the disorder, so an individual might experience themselves as sleeping well, just much later than the norm. People with this night owl schedule can however, experience being very sleepy during the day, and there are a substantial number of individuals, about 50%, that have comorbid depression or behavior problems.

When is being a night owl a problem? When it interferes with work or school, or when it is evident it is causing depression or other behavioral health issues. It then ceases to be just a syndrome and is classified as a disorder.

Causes of DSP

“Causes for delayed sleep disorder include a combination of both genetic and environmental factors such as a family history of delayed sleep,” explains Dr. Dulka. “Other causes include poor sleep hygiene like being exposed to too much light in the evening.”

Research indicates around 40% of people with the disorder have a family history of delayed sleep, or a family member with the disorder, pointing towards a predisposition. Recent research has explored the role of human leucocyte antigen DR1 in this disorder along with genetic polymorphisms in the PER3 gene (related to circadian rhythms) in DSPD.

Poor sleep hygiene can also contribute to having delayed sleep phase conditions. The most significant sleep hygiene factor is light, and especially a lack of outdoor morning light or too much light in the evening, can affect melatonin production and contribute to delayed sleep.

Advanced Sleep Phase Disorder (ASP)

The opposite of DSP, people with ASP generally go to sleep and wake up several hours earlier than the average person. These “early birds” generally wake between 2 a.m. and 5 a.m. and go to bed between 6 p.m. and 9 p.m. ASP more often affects middle-aged adults and the likelihood of developing it increases with age. This disorder may also be a normal part of aging.

Symptoms of ASP

The primary symptom of advanced sleep phase disorder is an earlier than normal sleep wake cycle. To receive a formal diagnosis, the release of sleep hormones like melatonin, and the lowering of the body’s temperature, must also be reset to that earlier schedule. You can consult a sleep specialist and have a sleep study done to make a determination about advanced sleep phase disorder, and to rule out other sleep disorders or comorbidities like sleep apnea.

There are additional symptoms that are secondary to advanced sleep phase disorder and more anecdotal. People report feeling very sleepy and are sometimes unable to stay awake for social situations if they occur in the evening. They further report feeling isolated, because their early sleep schedule dictates an inability to participate in evening activities.

If individuals push past the need for an early bedtime and stay up later, they cannot generally make up the lost sleep on the other end, and can easily experience sleep deprivation and accompanying mental and physical health problems. Depression or other mental health challenges can be secondary symptoms if sleep is not sufficient.

Causes of ASP

Research has yet to pinpoint a cause. There is a known genetic link and one out of two children of advanced sleep phase disorder patients will contract the disorder. Because it is more common as we age, there is thought to be a link to hormone production which decreases as we grow older.

In a recent study, Dr. Louis Ptacek, a researcher, and his team looked at 2,422 patients from a sleep center and followed them for 9.8 years. They collected data on their sleep schedule preference over this period of time. Out of these patients, 1,748 were there for obstructive sleep apnea symptoms, and each was individually screened for ASPD symptoms.

The results of this study shows that of the group, 12 met the advanced sleep phase (ASP) or familial advanced sleep phase (FASP) criteria, and 4 of the 12 declined study participation. Here are the numerical results:

  • 3% of the obstructive sleep apnea (OSA) group also had advanced sleep phase (ASP)
  • This totals out to 1 out of every 300 people in the scale of the general population
  • 21% of people with advanced sleep phase (ASP) inherited it, making their disorder familial advanced sleep phase (FASP)

Because of the 4 that declined to participate, this number could be even higher. Dr. Ptacek says “We hope the results of this study will not only raise awareness of advanced sleep phase and familial advanced sleep phase but also help identify the circadian clock genes and any medical conditions that they may influence.”

From what we know about the study, it seems that a large amount of patients with ASP got it as a result of the disorder being passed down in the family. Older adults are also at an increased risk of ASP due to the circadian rhythm shifts that happen naturally at this time as we age.

Non-24-Hour Sleep-Wake Disorder (non-24)

Also called Free Running or Nontrained Disorder, this condition mainly affects people who are blind with no light perception and are therefore unable to receive the usual environmental time cues. It occurs when someone’s alertness and performance patterns are totally desynchronized from the normal 24-hour day. Sleep tends to occur one or two hours later each day, following a so-called “free-running” cycle of 25 hours or more. It typically takes a few weeks to complete a full cycle.

Irregular Sleep-Wake Rhythm Disorder (ISWRD)

This sleep disorder is most often seen in people who suffer from Alzheimer’s disease or other forms of dementia. It occurs when a person takes numerous naps at irregular times throughout a 24-hour period with no main nighttime, or polyphasic, sleep episode.

Total sleep time may be similar to the average person’s but the sleep pattern is highly irregular and socially impractical. Sufferers generally complain of chronic insomnia, excessive sleepiness, or both. Body temperature also tends to fluctuate wildly throughout the 24-hour period, but it’s usually in synch with the person’s sleep cycle.

Jet Lag Disorder

As the name implies, Jet Lag Disorder occurs when someone has quickly (generally by airplane) to another time zone. In this new location, the person must sleep and wake at times that don’t align with their body clock. The severity of a person’s jet lag increases with the number of times zones that they cross. 

Typically, it is harder to adjust to eastward travel than westward travel. While all age groups can experience jet lag, it tends to be worse in older adults with symptoms felt more profoundly and the recovery more prolonged. Other factors that increase the severity of insomnia and impaired alertness associated with air travel include sleep deprivation, prolonged uncomfortable sitting positions, air quality and pressure, stress, and excessive caffeine and alcohol use. The good news is that jet lag is a temporary condition.

Shift Work Sleep Disorder

Shift work disorder occurs when a person’s work hours are scheduled at a time when most people are sleeping. People with this condition can easily become sleepy during their work shift, and it can be a struggle for them to sleep during the day when others are awake. Shift work disorders generally affect those working night shifts, early morning shifts, and rotating shifts. 

Depending on the type of shift, time of day or circadian preferences may influence the ability to adjust to shift work. For example, people described as morning types appear to obtain shorter daytime sleep after a night shift. Persons with medical, psychiatric, and other sleep disorders such as sleep apnea and those with a strong need for stable hours of sleep may be at particular risk.

What are the Symptoms of CRSD? 

The body’s circadian rhythm controls things like core temperature, alertness, appetite, hormone secretion, etc., over the 24-hour day, and it also influences the times of day when a person is ready to sleep and wake. If the person’s extrinsic circumstances are such that they are not able to keep to this internal timetable, then sleep patterns may be impacted, sometimes severely. 

Thus, the problem is not that sufferers are unable to sleep, but that their natural schedules are not compatible with the schedules and demands of modern life, leading to an accumulating sleep debt and daytime sleepiness.

Symptoms include:

  • Insomnia (difficulty falling asleep or staying asleep)
  • Excessive daytime sleepiness
  • Difficulty waking in the morning or waking too early and not being able to fall back asleep
  • Sleep deficit
  • Depression
  • Strained relationships
  • Poor work or school performance
  • Inability to meet social obligations

How Serious are Circadian Rhythm Sleep Disorders?

If left untreated, CRSDs can lead to more serious side effects:

  • Cancer
  • Dementia
  • Heart disease 
  • High blood pressure
  • Other sleep disorders
  • Depression and mood disorders
  • Psychiatric disorders
  • Type 2 diabetes
  • Poor balance
  • Obesity
  • Weakened bones
  • Weakened immune system
  • Accidents (car accidents, falls)

What Causes Circadian Rhythm Sleep Disorders

Circadian rhythm sleep disorders occur due to phase shifts in individual circadian clocks. Most of these disorders (DSP, ASP, non-24, ISWRD) are largely genetic in origin, often involving the so-called PER and CLOCK genes. Shift Work Disorder and Jet Lag Disorder arise from same root cause — circadian rhythm phase shifts — but the reasons for their incidence are more social or occupational than medical.

Some causes of CRSD include:

  • Shift work
  • Time zone changes
  • Pregnancy
  • Medications
  • Changes in your daily routine (staying up later than usual or waking earlier than usual)
  • Cognitive problems (Alzheimer’s disease or Parkinson’s disease)
  • Mental health problems
  • Menopause

How are Circadian Rhythm Sleep Disorders Diagnosed? 

CRSDs are usually only diagnosed when the phase advance or phase delay differs from the norm by at least two hours (i.e. it is more extreme than just an individual’s tendency towards being a “night owl” or an “early bird” due to their chronotype). In some cases of a CRSD, the phase shifts may be three to five hours or more.

You will need to see a doctor or a sleep specialist to be diagnosed and ultimately treated for a circadian rhythm sleep disorder. Your doctor will probably ask you to record when and how well you sleep over a period of time. They may also have you wear a small device called an actigraphy on your wrist to record your movements so they can better understand your sleep cycle. 

How to Treat Circadian Rhythm Sleep Disorders

Treatments used to treat your CRSD will depend on your specific condition and may include: 

  • Bright light therapy, using bright light at desired wake-up times, and darkness at desired sleep times.
  • Chronotherapy, a process of gradually adjusting your bedtime until it reaches your desired bedtime to reset your circadian clock.
  • Oral supplements like melatonin to induce sleepiness.
  • Oral medications, like stimulants to promote wakefulness or hypnotics, to promote sleepiness. 
  • Lifestyle changes, such as sticking to a strict nap schedule and controlling your exposure to light, and cutting back on substances like caffeine or nicotine before bed.
  • Sleep hygiene, such as improving your sleep environment.


An estimated 3% of adults suffer from a circadian rhythm sleep disorder, but some studies suggest the number may actually be higher as these sleep disorders are often confused with insomnia. In actuality, as many as 10% of adults and 16% of adolescents diagnosed with another sleep disorder may actually suffer from CRSD. 

While some sleep disorders caused by a disruption in the circadian rhythm can be self-limiting, like jet lag, others, if left untreated, can lead to serious adverse medical, psychological, and social consequences. Thus, it is important that people who experience unusual sleep patterns seek treatment from their doctor or a sleep specialist. 

Expert Bio

Expert Bio

Dr. Brooke Dulka is a medical writer and neuroscientist. She recieved her Ph.D. in biological psychology from the University of Tennessee, and she is currently a postdoctoral researcher at the University of Wisconsin-Milwaukee where she studies the neurobiology of memory.