ConditionBrain & nerves
Circadian Rhythm Sleep Disorders
Circadian rhythm sleep disorders occur when your internal body clock is out of step with the schedule you need to keep, or when the clock itself is not working properly. You can sleep normally, just at the wrong times, which causes insomnia at bedtime and sleepiness when you need to be awake. Common types are delayed sleep phase (night owls), advanced sleep phase, shift work disorder and jet lag. Timed light exposure, melatonin and consistent schedules are the main treatments.
Also called: Circadian rhythm sleep-wake disorders, body clock disorders, sleep timing disorders
At a glance
- What it is
- A mismatch between your body clock and the time you need to sleep and wake.
- Common types
- Delayed and advanced sleep phase, irregular rhythm, non-24-hour rhythm, shift work disorder and jet lag.
- Symptoms
- Difficulty falling asleep or waking at the desired time, daytime sleepiness and reduced performance.
- Diagnosis
- Sleep diaries and actigraphy for 1 to 2 weeks.
- Treatment
- Timed bright light, timed melatonin, fixed schedules and good sleep habits.
When to get help
See a doctor within a day or two
- Falling asleep while driving, or near-miss accidents from sleepiness
- Severe sleepiness at work in a safety-critical job
Book a routine appointment
- Being unable to fall asleep until very late and unable to wake for school or work, most days for 3 months
- Falling asleep very early in the evening and waking before dawn despite wanting to sleep longer
- Persistent sleepiness or insomnia linked to night shifts or rotating shifts
- Low mood or poor concentration linked to disrupted sleep timing
Usually safe to manage at home
- Jet lag after travel across time zones, which usually settles within a few days
How the body clock works
A master clock in the brain's hypothalamus (the suprachiasmatic nucleus) runs a cycle of a little over 24 hours. It is reset each day mainly by light entering the eyes, especially morning light. In the evening, darkness triggers release of melatonin, which promotes sleep. Meal timing, activity and social cues also help keep the clock aligned.
When the clock runs too late, too early, irregularly or out of sync with the light-dark cycle, sleep timing shifts.
Types of circadian rhythm sleep disorders
| Type | Pattern | Who is affected |
|---|---|---|
| Delayed sleep phase disorder | Falls asleep very late (often 2 to 6 a.m.), wakes late; sleep is normal if allowed | Teens and young adults most often |
| Advanced sleep phase disorder | Sleepy early evening (6 to 9 p.m.), wakes very early (2 to 5 a.m.) | Older adults; some families |
| Irregular sleep-wake rhythm | Sleep broken into several short periods across 24 hours | People with dementia, brain injury, in institutions |
| Non-24-hour sleep-wake disorder | Sleep time drifts later each day | Mostly totally blind people |
| Shift work disorder | Insomnia and sleepiness from working nights or rotating shifts | Shift workers |
| Jet lag disorder | Temporary mismatch after crossing time zones | Travelers, worse flying east |
Symptoms
- difficulty falling asleep at the desired time
- difficulty waking in the morning, or waking far too early
- daytime sleepiness and fatigue
- poor concentration, memory and mood
- reduced performance at school or work
- in shift workers, more accidents and errors
Unlike in insomnia, sleep quality is usually normal when the person sleeps at their preferred time.
Causes and risk factors
- Genetics: variants in clock genes, especially for advanced and delayed phase
- Adolescence: the body clock naturally shifts later in the teen years
- Light habits: late-night screens and bright light, little morning light
- Shift work and travel
- Aging and neurological conditions such as dementia
- Blindness: no light signal to reset the clock
- Mental health conditions: delayed phase is common with depression and ADHD
Diagnosis
- Sleep diary: record bedtimes, wake times and naps for at least 7 to 14 days.
- Actigraphy: a wrist device that tracks rest and activity patterns.
- Questionnaires on chronotype (morning or evening preference).
- Dim light melatonin onset testing in some sleep centers.
- Sleep study only if another disorder such as sleep apnea or narcolepsy is suspected.
Treatment
Light therapy
- Delayed phase: bright light (about 10,000 lux light box or outdoor sunlight) for 20 to 30 minutes soon after waking, and avoiding bright light and screens in the evening.
- Advanced phase: bright light in the early evening.
- Shift work: bright light during the shift and dark glasses on the way home.
Melatonin
Low-dose melatonin taken several hours before the desired bedtime helps shift the clock earlier in delayed phase disorder and non-24-hour rhythm. Timing matters more than dose. In the US melatonin is sold as a supplement, so quality varies; discuss use with your doctor, especially for children. Tasimelteon is FDA-approved for non-24-hour disorder in blind people.
Schedule changes
- Keep fixed wake times, including weekends.
- Shift bedtime gradually, 15 to 30 minutes every few days.
- For jet lag, start shifting sleep before travel and seek light at the right time at your destination.
- For shift workers, keep rotations forward (day, evening, night), sleep in a dark, quiet room and use planned naps.
Sleep habits
Limit caffeine after midday, avoid alcohol near bedtime, exercise regularly and keep the bedroom dark and cool.
Sedating sleep pills are generally not recommended as a main treatment.
Frequently asked questions
What is the most common circadian rhythm sleep disorder?
Delayed sleep phase disorder is the most common intrinsic type, especially in teenagers and young adults. Shift work disorder and jet lag are very common in the general population but are caused by external schedules.
Can a circadian rhythm disorder be fixed?
Many people improve with consistent schedules, morning light and properly timed melatonin. Results depend on sticking with the routine, because the body clock tends to drift back. Shift work disorder improves most when shift patterns can be changed.
Is being a night owl a disorder?
Not by itself. Many people prefer later sleep and function well when they can follow it. It becomes delayed sleep phase disorder when the late schedule causes significant problems, such as missing school or work or chronic sleep deprivation.
How long does jet lag last?
Jet lag typically lasts about 1 day for each time zone crossed, often longer when flying east. Getting light at the right time, adjusting meals and short-term melatonin can speed adjustment.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Sleep Medicine: Clinical practice guideline for intrinsic circadian rhythm sleep-wake disorders
- National Heart, Lung, and Blood Institute: Circadian rhythm disorders
- Sleep Foundation: Circadian rhythm sleep disorders
- MedlinePlus: Circadian rhythm sleep disorders
- CDC: Shift work and long work hours