I'm going to throw my experience with melatonin out there. I took melatonin for more than 10 years, then quit for about 6 months or so. Next time I took it I was awake all night tossing and turning. Didn't sleep at all. Very jittery. Tried again a couple of weeks later and same thing happened. Threw the bottle away and have never touched melatonin since. I truly can't explain it, and don't even know if that is a common occurrence, or it was just something within me that reacted to it.