TweetI doubt that there is any problems from taking it long term. I think the body produces it from serotonin, by cleaving off a couple methyl groups. I take it along with tryptophan and gaba. I ran out of melatonin about a month ago and havent taken any and am sleeping just as good with just tryptophan. Some nights I forget the tryptophan and still sleep good so I who knows. lol