Just taking it once doesn't cause withdrawal, it only happened after two weeks for me. Just because it is a low concentration doesn't change the fact it is a strong mind altering drug that when if you stop taking it suddenly it will cause side effects in many cases. It makes you sleep like a log so insomnia for a few days if you stop taking it is to be expected like most sleeping pills. Can be pretty useful for some people though, I don't think it is for me.