The circadian rhythm is the internal biological cycle of approximately 24 hours that regulates sleep, body temperature, hormonal secretion, and many other physiological processes. The suprachiasmatic nucleus (SCN) of the hypothalamus acts as the master clock and synchronizes primarily with sunlight. Disruptions — travel, shift work, nighttime screens — impair sleep.
Concept origin
Hall, Rosbash, and Young received the Nobel Prize in Physiology or Medicine (2017) for discovering the molecular mechanisms of the circadian clock. Czeisler and colleagues at Harvard have documented for decades how artificial nighttime light shifts the cycle and compromises health.
Therapeutic approach
Bright light therapy in the morning (10,000 lux, 20-30 minutes) advances the cycle in people with delayed sleep phase. Maintaining regular sleep schedules and natural light exposure upon waking are the most potent interventions for synchronizing the circadian rhythm.
Related concepts
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