Within each 24-hour period, the regular fluctuation from high to low points of certain bodily functions and behaviors.
Gen Psych, CH 4, pp. 110

For more information on Circadian Rhythm see:
Circadian Rhythm
Circadian rhythm Fact Sheet
Scientific Reference to Circadian Rhythm

For disorders and problems with circadian rhythm see:
Sleep Disorders
Diseases and Conditions relating to Circadian Rhythm
Sleeplessness and Curcadian Rhythm Disorder


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  • I don't think he's a morning person!
  • The newborn baby slept all day at the hospital, now the mother cannot get her back to a normal sleeping schedule.


  • For purposes of Daylight Savings time, We must remember the phrase "Fall backward to Spring Foward". This reminds us to set our clocks either an hour ahead or behind so our circadian rhythms can sync with the changing sun.
  • C. I. R. C. A. D. I. A. N. R. H. Y. T. H. M.

Articles in the News:

Possible molecular link between circadian rhythm disturbances and increased inflammatory response.
Chemical that regulates biological clock could foster new diabetes treatments.
Documentary: No Sleep for a Week
Circadian Rhythm and Depression