Proceedings of the National Academy of Sciences, throws cold water on that dream. A new set of researchers replicated part of the 2014 study’s findings: That is, from 1999 to 2010, it’s true that the introduction of medical-marijuana laws was associated with a decline in opioid-overdose deaths. But when the researchers included states that introduced laws between 2010 and 2017, the direction of the relationship reversed. Instead of a reduction in opioid overdoses, medical marijuana was associated with a 23 percent increase in overdose deaths.
