Circadian Rhythm Sleep Disorders (CRSD)

By Jennifer Walker-Journey

Apr 16th, 2021

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)

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.

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.

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? 

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 of CRSDs 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 These 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.