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Sleeplessness and Circadian Rhythm Disorder Topic Guide
Sleeplessness and Circadian Rhythm Disorder: A person's circadian rhythm is an internal biological clock that regulates a variety of biological processes according to an approximate 24-hour period. A disorder of the circadian rhythm may cause sleeplessness on at transient or chronic basis. The disorder can be caused by:
Seasonal Depression (SAD) Seasonal affective disorder (SAD) is a type of depression that is tied to seasons of the year. Symptoms include depressed mood, fatigue, feelings of worthlessness, and poor concentration. Treatment may incorporate bright-light therapy and antidepressants.