Scientific American reported –
Some people, no matter what they do, simply cannot fall asleep until the wee hours—and do not feel rested unless they get up much later than most of us. These night owls may have a common form of insomnia called delayed sleep phase disorder (DSPD), which studies have suggested is at least partly heritable. Now researchers at the Rockefeller University and their colleagues have uncovered a genetic mutation that may explain why this condition sometimes runs in families. And it could elucidate the mechanism that causes these often awkward sleep schedules.
DUMMR.com 