One out of every five children in America under the age of 14 uses melatonin as a sleep aid, according to new research out this month from the University of Colorado Boulder. Melatonin is a hormone produced by the brain that regulates the sleep cycle. The American Academy of Sleep Medicine has issued an advisory asking parents to talk with a pediatrician before using the hormone long-term in children. Some products tested last year showed mislabeled products that contained 300-percent more melatonin than listed on the bottle. Side effects of taking too much can include everything from headaches to itchy skin and in extreme cases, irritability and depression.