Circadin is just melatonin but it is configured as slow release and in most countries requires a doctors prescription as I have. Impact on me is slow pleasant tiredness and no feeling of sleep medication because after all it is i believe a complex brain produced hormone - but I am not a doctor - but my Mayo trained neurologist suggests it as a possible alternative to Ativan to get a better quality of sleep and I agree - it works very well with zero side effects but is relatively expensive.