Circadian Rhythm Sleep Disorders
Reviewed by our editorial team
Last updated: 2026-04-01
Circadian Rhythm Sleep-Wake Disorders (CRSWDs) occur when your internal biological clock—the 'master clock' in your brain—is not synchronized with your environment. This clock regulates not only sleep but also body temperature, hormone release, and metabolism. When it is misaligned, you may struggle to sleep when you need to and feel overwhelmingly tired when you need to be awake.
These disorders can be caused by internal factors, such as genetic predispositions, or external factors like shift work or travel across time zones. Unlike insomnia, where the ability to sleep is impaired, CRSWDs are primarily problems of timing. If allowed to sleep on their own preferred schedule, many people with these disorders would sleep quite well.
Delayed Sleep Phase Disorder (DSPD)
DSPD is common in teenagers and young adults. It is characterized by a natural sleep-wake cycle that is delayed by two or more hours beyond the conventional bedtime. 'Night owls' with DSPD often cannot fall asleep before 2 AM or 4 AM and find it extremely difficult to wake up for morning commitments.
When forced to wake up early for school or work, they suffer from chronic sleep deprivation. However, on weekends or vacations when they can sleep from 3 AM to 11 AM, their sleep quality is usually normal and they feel refreshed.
Advanced Sleep Phase Disorder (ASPD)
Opposite to DSPD, Advanced Sleep Phase Disorder involves a sleep-wake cycle that is several hours earlier than normal. People with ASPD may feel compelled to sleep as early as 6 PM or 8 PM and wake up between 2 AM and 5 AM.
This condition is more common in older adults. While it might not cause as much daytime sleepiness if the person can sleep their full duration, it can significantly interfere with social lives and evening activities. Like DSPD, the sleep itself is usually of good quality, just misplaced in time.
Non-24-Hour Sleep-Wake Disorder
Non-24 is a condition where an individual's internal clock is slightly longer than 24 hours. Because the clock doesn't 'reset' each day, their sleep times gradually shift later and later around the clock over several weeks. One week they may sleep at night, and the next they may be sleeping during the day.
This disorder is most common in individuals who are totally blind, as they lack the light cues (zeitgebers) that normally synchronize the master clock to the sun. However, it can occasionally occur in sighted individuals due to neurological issues.
Treatment: Resynchronizing the Clock
Treatment focuses on shifting the internal clock back into alignment using light therapy and melatonin. Light therapy involves exposure to bright, specialized lamps at specific times of the day to 'signal' the brain that it is time to be awake. Melatonin is used as a 'chronobiotic' to signal the onset of the biological night.
Chronotherapy is another technique where bedtime is gradually delayed (or advanced) until the desired schedule is reached. Success requires strict adherence to a schedule, even on weekends, as the circadian system is highly sensitive to inconsistent signals.
When to Speak With a Doctor
See a sleep specialist if your natural sleep schedule is causing significant problems with your work, education, or social responsibilities.
Frequently Asked Questions
References
- [1]Circadian Sleep Disorders Network. What is CRSD?
- [2]Sleep Foundation. Circadian Rhythm Sleep Disorders.
- [3]American Academy of Sleep Medicine. Treatment of Circadian Rhythm Sleep-Wake Disorders.
The information on this page is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for diagnosis and treatment.