Circadian rhythm sleep disorder


Circadian Rhythm Sleep Disorders are disruptions in the circadian rhythm—the human body’s internal clock, which regulates various biological processes. The word circadian comes from the Latin words “circa" (meaning “around”) and “dia” (meaning “day”).

The circadian "clock" in humans is mainly located in the suprachiasmatic nucleus, a group of cells located in the hypothalamus (a portion of the brain). Circadian rhythms are important in determining human sleeping patterns. These rhythms regulate patterns of brain wave activity, hormone production, cell regeneration, and other biological activities linked to a 24-hour cycle.


Circadian rhythm disorders can be caused by factors that include:

  • Jet lag (or time zone changes)
  • Shift work (working at night Pregnancy Changes in regular routine


  • Excessive sleepiness
  • Insomnia
  • Difficulty rousing from sleep
  • Early sleep onset
  • Waking earlier than desired Lack of alertness