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Original Investigation
Health Care Policy and Law
April 2, 2018

Association Between US State Medical Cannabis Laws and Opioid Prescribing in the Medicare Part D Population

Author Affiliations
  • 1Department of Public Administration & Policy, University of Georgia, Athens
  • 2Department of Health Policy & Management, University of Georgia, Athens
JAMA Intern Med. Published online April 2, 2018. doi:10.1001/jamainternmed.2018.0266
Key Points

Question  What is the association between US state implementation of medical cannabis laws and opioid prescribing under Medicare Part D?

Findings  This longitudinal analysis of Medicare Part D found that prescriptions filled for all opioids decreased by 2.11 million daily doses per year from an average of 23.08 million daily doses per year when a state instituted any medical cannabis law. Prescriptions for all opioids decreased by 3.742 million daily doses per year when medical cannabis dispensaries opened.

Meaning  Medical cannabis policies may be one mechanism that can encourage lower prescription opioid use and serve as a harm abatement tool in the opioid crisis.


Importance  Opioid-related mortality increased by 15.6% from 2014 to 2015 and increased almost 320% between 2000 and 2015. Recent research finds that the use of all pain medications (opioid and nonopioid collectively) decreases in Medicare Part D and Medicaid populations when states approve medical cannabis laws (MCLs). The association between MCLs and opioid prescriptions is not well understood.

Objective  To examine the association between prescribing patterns for opioids in Medicare Part D and the implementation of state MCLs.

Design, Setting, and Participants  Longitudinal analysis of the daily doses of opioids filled in Medicare Part D for all opioids as a group and for categories of opioids by state and state-level MCLs from 2010 through 2015. Separate models were estimated first for whether the state had implemented any MCL and second for whether a state had implemented either a dispensary-based or a home cultivation only–based MCL.

Main Outcomes and Measures  The primary outcome measure was the total number of daily opioid doses prescribed (in millions) in each US state for all opioids. The secondary analysis examined the association between MCLs separately by opioid class.

Results  From 2010 to 2015 there were 23.08 million daily doses of any opioid dispensed per year in the average state under Medicare Part D. Multiple regression analysis results found that patients filled fewer daily doses of any opioid in states with an MCL. The associations between MCLs and any opioid prescribing were statistically significant when we took the type of MCL into account: states with active dispensaries saw 3.742 million fewer daily doses filled (95% CI, −6.289 to −1.194); states with home cultivation only MCLs saw 1.792 million fewer filled daily doses (95% CI, −3.532 to −0.052). Results varied by type of opioid, with statistically significant estimated negative associations observed for hydrocodone and morphine. Hydrocodone use decreased by 2.320 million daily doses (or 17.4%) filled with dispensary-based MCLs (95% CI, −3.782 to −0.859; P = .002) and decreased by 1.256 million daily doses (or 9.4%) filled with home-cultivation–only-based MCLs (95% CI, −2.319 to −0.193; P = .02). Morphine use decreased by 0.361 million daily doses (or 20.7%) filled with dispensary-based MCLs (95% CI, −0.718 to −0.005; P = .047).

Conclusions and Relevance  Medical cannabis laws are associated with significant reductions in opioid prescribing in the Medicare Part D population. This finding was particularly strong in states that permit dispensaries, and for reductions in hydrocodone and morphine prescriptions.

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    1 Comment for this article
    Cannabis and pain
    DAVID KELLER, MD, MS | Retired internist

    The authors cite 7 papers as providing "clinical evidence that cannabis can be used to manage pain," references 17-23. The PubMed abstracts for these papers reveal that only three were clinical studies of the efficacy of cannabis as an analgesic; one was a safety study that did not report on efficacy, and 3 were review papers that generally pointed out the dearth of good studies of cannabis as an analgesic.

    The 3 clinical studies tested smoked cannabis versus placebo, but not against an opioid, NSAID, or other analgesic known to be effective against moderate to severe somatic
    pain. No assessment of blinding efficacy was reported, a crucial deficiency when testing a drug with obvious psychoactive effects that could easily lead to unmasking of the active drug and expectation effects rivaling the modest reported analgesic efficacies of cannabis. Finally, the pain indications tested in the 3 clinical trials were all rare neuropathic syndromes, a type of pain which is known to respond poorly to opioids and thus be an unlikely source for reduction of opioid prescribing.

    The proven benefits of cannabis do not yet, and might never, live up to the high hopes of its advocates, who would do well to remember that cannabinoids, like caffeine, nicotine and other plant neurotoxins, evolved to make the plant less likely to be eaten, by injuring or impairing the CNS of animals that consume too much of the plant.