Melatonin is great stuff, really helps my son fall asleep much more easily. Good info here:
http://en.wikipedia.org/wiki/MelatoninA few choice bits from the wiki page:
"Besides its function as synchronizer of the biological clock, melatonin also exerts a powerful antioxidant activity"
"Individuals with autism spectrum disorders (ASD) may have lower than normal levels of melatonin"
"Research shows that after melatonin is administered to ADHD patients on methylphenidate, the time needed to fall asleep is significantly reduced. Furthermore, the effects of the melatonin after three months showed no change from its effects after one week of use"