this finding , as well as the central importance of melatonin as a hormonal mediator of photoperiodic changes on seasonal rhythms in animals , led us to test the hypothesis that melatonin mediates the effects of shortening days on the winter symptoms of sad and that the modification of melatonin secretion by bright light mediates its antidepressant effects .
C0025219
melatonin
C0085159
sad