Bradford AC, et al. - The correlation between prescribing patterns for opioids in Medicare Part D and the implementation of state medical cannabis laws (MCLs) was analyzed in the US from 2010 through 2015. Variation was noted by type of opioid, with statistically notable, estimated negative associations for hydrocodone and morphine. Data shed light on the connection between medical cannabis laws with marked reductions in opioid prescribing in the Medicare Part D population. Yielded results were particularly strong in states that permit dispensaries, and for reductions in hydrocodone and morphine prescriptions.