Definition
The circadian rhythm is the roughly 24-hour biological cycle that organizes sleep, hormones, metabolism, temperature, and cognition. It is driven by a master clock in the suprachiasmatic nucleus and countless peripheral clocks in tissues.
Why it matters
Almost every physiological system runs on circadian time. Ignoring this leads to endless friction with the body. Working with circadian biology is a foundational skill of care.
The Science
The suprachiasmatic nucleus of the hypothalamus is entrained primarily by light through the retinohypothalamic tract. It coordinates peripheral clocks in liver, gut, immune organs, and elsewhere. Disruption of circadian rhythms is linked to metabolic disease, mood disorders, cardiovascular risk, and cancer risk.
The NSI Perspective
NSI treats circadian rhythm as one of the deepest organizing systems of the nervous system. Regulation without respect for it is a losing battle.
Clinical Implications
Consistent sleep–wake timing, morning light exposure, and meal timing are legitimate clinical interventions with broad effects.
Practical Application
One of the most powerful sleep interventions is the simplest — the same wake time, most days, seen by daylight soon after.
References
- 1.Roenneberg T, Merrow M. The circadian clock and human health. Curr Biol. 2016;26(10):R432–R443.