Health implications of disrupted circadian rhythms and the potential for daylight as therapy.

1170 May 2015 F or many thousands of years, the sun was our only source of light, and human behavior followed a natural day–night cycle. This milieu began to change approximately 150 yr ago with the invention of incandescent lighting. Electric lighting disrupted our behavioral dependence on the day–night cycles of the sun and facilitated alterations in our circadian sleep–wake cycles. recent research has begun to identify the physiologic consequences of unnatural light exposure and subsequently altered circadian rhythms.1 In this article, we review the molecular basis of circadian rhythms and discuss the established connection between disrupted circadian rhythms and clinical disease. We also explore the concept of daylight as therapy to restore disrupted circadian rhythms and improve clinical outcomes.