So, I am not finding the specific article, but google is full of articles about how marijuana is reducing opioid use and some where they are even using marijuana as treatment for opiod abuse. As you know, heroin is obvsly an opioid. It would seem that a logical next step would be that marijuana legalization may even reduce the amount of heroin addicts as much of the rise in heroin use, recently, has been ppl chasing a pain killer addiction and substituting heroin for oxy as it is less expensive.