Furthermore, the study shows that people engaged in the non-medical use of prescription opioids rarely use heroin. Also, the transition to heroin for people abusing prescription opioids occurs at a lower rate than for others. The research indicates that the primary causes in the increase in heroin use and associated overdoses are lower market prices and higher purity for heroin.
Links
[1] https://drive.google.com/file/d/0B5ameKn-SJEXVER6bXlmRl9naVdMTy1YSjdZZ1ZQd2tOVXln/view?usp=sharing
[2] http://rethinkpot.org/tags/opioid
[3] http://rethinkpot.org/tags/heroin