Exposing preschoolers to an hour of bright light before bedtime is not a good idea, according to new CU 麻豆影院 study. It disrupts their sleep patterns, almost completely shuts down their production of the sleep-promoting hormone melatonin, keeping it suppressed for at least 50 minutes after light鈥檚 out, says lead author Lameese Akacem with the Sleep and Development Laboratory at CU 麻豆影院.