If the drug is either not very harmful like pot or you're getting pure doses, then whether or not you enter a negative feedback spiral with it is largely up to the mental health and circumstances of the user. The results are skewed simply because so many folks who use are already in a terrible mental place and using is simply a symptom. A normal, well adjusted person could (assuming it was legal) most likely smoke all kinds of meth without any more chance of it destroying their lives than if they were drinking beer.