LIGHT TREATMENT FOR SLEEP DISORDERS - CONSENSUS REPORT .1. CHRONOLOGYOF SEMINAL STUDIES IN HUMANS

Examination of the influence of the light-dark cycle on circadian rhyt hmicity has been a fundamental aspect of chronobiology since its incep tion as a scientific discipline. Beginning with Bunning's hypothetical phase response curve in 1936, the impact of timed light exposure on c ircadian rhythms of literally hundreds of species has been described. The view that the light-dark cycle was an important zeitgeber for the human circadian system, as well, seemed to be supported by early studi es of blind and sighted subjects. Yet, by the early 1970s, based prima rily on a series of studies conducted at Erling-Andechs, Germany, the notion became widely accepted that the light-dark cycle had only a wea k influence on the human circadian system and that social cues played a more important role in entrainment. In 1980, investigators at the Na tional Institute of Mental Health reported that bright light could sup press melatonin production in humans, thereby demonstrating unequivoca lly the powerful effects of light on the human central nervous system. This finding led directly to the use of timed bright light exposure a s a tool for the study and treatment of human circadian rhythms disord ers.