Circadian Rhythm Disorders

Circadian Rhythm Disorders

What Is Circadian Rhythm?

Circadian rhythm is the body’s internal timekeeper. It is based on the 24-hour light/dark cycle and allows for the alignment of your body processes to the external light-dark environment.

It is reset every day through exposure to light and dark. The circadian rhythm helps you fall asleep and wake up. Additionally, it plays a role in body temperature, digestion, and hormone function. (eg melatonin, cortisol).

A cycle of sleep starting groggy to more alert and rhythm dips as you get ready for sleep.

What Is A Circadian Rhythm Disorder?

Situations that alter day-night light exposure may disrupt your circadian rhythms. This may result in a sleep-related disorder, as well as physical and psychological problems.

The two most common circadian rhythm disorders are shift work disorder and jet lag disorder. There are also several other less common disorders.

Shift Work Disorder

Shift work refers to a work schedule outside of the usual 9:00 to 5:00 workday. It may be regular or irregular nights, early morning work, or rotating days and nights. Shift work disorder is when your work results in sleep problems, as well as trouble with daytime alertness and performance.

1 out of 5 jobs in the U.S. involves shift work. Health care professionals and first responders are examples of professions susceptible to shift work disorders. However, shift workers don’t always develop disorders.

Jet Lag Disorder

Jet lag disorder is a short-term disorder due to travel across different time zones. It affects the timing of your sleep-wake cycle when going from one time zone to another. Long distance business travelers and flight attendants and pilots may be affected.

Social Jet Lag Disorder

A related, but much more common disorder, is called social jet lag. Its effects are similar to jet lag disorder, but with a different cause. Although there is no change in time zone, there is a significant change in sleep-wake patterns throughout the week.

Social jet lag is often associated with differences between weekday and weekend sleep schedules. Children in daycare or school may have regular bedtime and wake schedules on weekdays, but with much different weekend or vacation sleep-wake times. Or, with adults, they may have regular work-week sleep and wake times, but with days off or vacations, they stay up longer and sleep late.

What Are The Symptoms Of Circadian Rhythm Disorder?

Symptoms of circadian rhythm disorder vary from person to person. They include:

  1. Insomnia or trouble sleeping

  2. Daytime sleepiness and impaired function

  3. Cognitive (thinking) difficulties

  4. Decreased alertness

  5. Poor job/school performance

  6. Physical discomforts, generally feeling unwell

How Are Circadian Rhythm Disorders Evaluated?

Shift work and jet lag disorders are evaluated in slightly different ways.

(1) Actigraphy - measuring day/night sleep characteristics using a device worn on the wrist

What Are The Therapies For Circadian Rhythm Disorders?

Treatment for circadian rhythm disorders in the U.S. include:

  1. Planning for and scheduling sleep

  2. Scheduling light exposure

  3. Melatonin supplements

  4. Stimulants (eg - caffeine) (2,3)

  5. Prescription sleep medicines (3)

  6. Prescription alerting agents (promote wakefulness)

(2) optional treatment for shift work disorder

(3) optional treatment for jet lag disorder

Circadian rhythm disorders also benefit from supportive family, social, and work environments. Efforts to increase support and decrease stress help in preventing sleep problems and mental health conditions, like anxiety and depression. Additionally, such measures help to improve work productivity which may be a problem in those with shift work disorder.

For More Information

American Academy of Sleep Medicine (2008). Circadian Rhythm Sleep Disorders Retrieved on 11-4-2020 from
National Institute of General Medical Sciences (2020). Circadian Rhythms. Retrieved on 11-4-2020 from