The Influence of Light on Mood

Abstract

Light is the most important environmental signal for the mammalian circadian system, and is detected exclusively by the eyes via specialized ganglion cell photoreceptors. Cycles of light and darkness relayed by the retina entrain suprachiasmatic nuclei neural activity, which in turn entrains the rhythmic production and secretion of melatonin from the pineal gland. Deficiencies on the daily and seasonal pattern of melatonin secretion seem to be one of the main causes of mood disorders. Since several studies confirmed that depressed patients show low concentrations of melatonin at night and that this could be an individual trait marker, the objective of this study was to test a hypothesis proposed by Stone to the lighting community in 1999 related to possible associations between glare sensitivity, melatonin response and depression. In the present research report, significant correlations were found between winter depression and melatonin production with age. On the other hand, sensitivity to glare significantly correlated with melatonin production during winter. Taken together, the results lend support for more investigation on these associations.