Have any links to this study?
The people I know for sure are on Heroin or whatever (one being my sister) started on RX painkillers that were sold on the streets and moved on to something harder. Her boyfriend (who is in jail now, but that is irrelevant) and her quite literally sought out Suboxone (which is one of the many drugs that can help with Opioid withdrawals) via Facebook, begging friends to buy it no matter the cost. Why? He was on probation for having possession of Heroin and paraphernalia years ago. I know he is on probation so I am pretty sure he has to piss for the probation officer, when he was trying to "get right" he went through awful withdrawals to piss clean, then he stops going to the probation officer a month later (hmmm, wonder why) and goes back to jail, gets out and does it all over again.
Part of the issue in my eyes is the discrimination of the inner city poor in the judicial system. They get popped for a minor possession charge initially, it sticks because they either can't afford an attorney, or can and get a two bit hackjob who couldn't give a shit less since he got his retainer fee. Public defense only offers so much defense.
I could get further into it but no use. I've ranted enough.