Circadian Rhythm Disorders

Circadian rhythm disorders involve disruptions to the ‘circadian rhythm’—the name for our ‘internal body clock’ that regulates our 24 hour cycle of biological processes through a combination of light sensitivity and protein and hormone production.

Our body clock keeps us synchronised with the cycle of daylight, and when this synchronisation is either delayed (Delayed Sleep Phase Syndrome) or advanced (Advanced Sleep Phase Syndrome), these circadian rhythm disorders can cause insomnia, fatigue, daytime sleepiness, and increased risk of depression. Jet Lag is a common body clock problem that most people experience, particularly with eastward travel.

Overview—What Are Circadian Rhythm Disorders?

Advanced Sleep Phase Disorder (ASPD) involves feeling too sleepy early in the evening and waking up too early in the morning. Sufferers may feel strong urges to fall asleep as early as 7pm, and after falling asleep quickly and sleeping well will wake at 1am or 2am and experience difficulty falling asleep again.

Delayed Sleep Phase Disorder (DSPD) involves difficulty falling asleep until very late into the night—as late as 4am or later in some cases—and then need to sleep in until late morning or early afternoon. In DPSD, waking up earlier despite a short sleep period doesn’t result in an earlier sleep time the following night.


Both ASPD and DSPD are often misdiagnosed as insomnia disorders, resulting in delayed diagnosis and inappropriate treatments. Evaluation with a Sleep Physician can ensure an accurate diagnosis and appropriate treatment plan.

What Causes Circadian Rhythm Disorders?

In both Advanced Sleep Phase Disorder (ASPD) and Delayed Sleep Phase Syndrome (DSPS), the circadian rhythm or internal body clock functions irregularly. Inappropriate exposure to light at the wrong time of the sleep-wake cycle can interfere with melatonin production and result in these common circadian rhythm disorders.

How are Circadian Rhythm Disorders Treated?

Both Advanced Sleep Phase Disorder (ASPD) and Delayed Sleep Phase Syndrome (DSPS) are treated by intervening to change or reset the internal body clock using a combination of bright light therapy and the use of the naturally occurring sleep hormone melatonin.

Small doses of melatonin may be prescribed for just before bedtime or in smaller doses midway during the sleep period. Bright light therapy involves stimulating the circadian rhythm systems with night light either from sunlight or from a special light box designed for the purpose.

Chronotherapy is a third form of treatment which involves carefully control sleeping and waking time with the aim of gradually changing bedtime, sleep and waking hours.

All three treatments interact in complex ways, and it’s imperative that a qualified sleep specialist designs and monitors the treatment program.