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Dialogues Clin Neurosci. 2012 Dec;14(4):448-53.

Light and chronobiology: implications for health and disease.

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Laboratory for Solar Energy and Building Physics, Ecole Polytechnique Federale de Lausanne, Switzerland.


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Environmental light synchronizes the primary mammalian biological clock in the suprachiasmatic nuclei, as well as many peripheral clocks in tissues and cells, to the solar 24-hour day. Light is the strongest synchronizing agent (zeitgeber) for the circadian system, and therefore keeps most biological and psychological rhythms internally synchronized, which is important for optimum function. Circadian sleep-wake disruptions and chronic circadian misalignment, as often observed in psychiatric and neurodegenerative illness, can be treated with light therapy. The beneficial effect on circadian synchronization, sleep quality, mood, and cognitive performance depends on timing, intensity, and spectral composition of light exposure. Tailoring and optimizing indoor lighting conditions may be an approach to improve wellbeing, alertness, and cognitive performance and, in the long term, producing health benefits.


affective disorder; bright light; circadian rhythm; circadian rhythm sleep disorder; daylight; entrainment; indoor lighting; intrinsically photosensitive retinal ganglion cell (ipRGC); light therapy; zeitgeber

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