In addition to inducing sleep, it also acts on different organs of body and influence their functions too. So it regulates the “biological clock” responsible for sleep/wake pattern. It has been seen that people engaged in night shift duty are prone to develop type II diabetes (DM Type II) mellitus, obesity and heart disease. Read more; http://clinispot.blogspot.com/2012/01/melatonin-and-risk-of-developing.html