Melatonin, as any hormone/supplement, helps if you have deficiency, and hurts if you have normal or high level already. If your natural melatonin production is

Melatonin, as any hormone/supplement, helps if you have deficiency, and hurts if you have normal or high level already. If your natural melatonin production is good enough, you are not going to feel effects, or even will get negative effects (I.e. people reporting hallucinations)