Medical and Recreational Cannabis Use Associated with Diminished Opioid Prescribing

Monday, November 12, 2018

R.L. Wynn

A recent study using Medicaid enrollee data showed that medical marijuana laws and adult-use marijuana laws were associated with lower opioid prescribing rates. A second study using data from the Medicare Part D population found that prescriptions filled for all opioids decreased by 2.11 million daily doses per year when a state instituted any medical cannabis law, and prescriptions for all opioids decreased by 3.742 million daily doses per year when medical cannabis dispensaries opened.

Medicaid Study

The Medicaid study’s objective was to examine the association of state implementation of medical and adult-use marijuana laws with opioid prescribing rates and spending among Medicaid enrollees. Its authors were from the Department of Health Management and Policy, the University of Kentucky College of Public Health at Lexington, Emory University School of Public Health in Atlanta, and the National Bureau of Economic Research in Cambridge, MA.

The study can be accessed at: Wen H, Hockenberry JM. Association of medical and adult-use marijuana laws with opioid prescribing for Medicaid enrollees. JAMA Internal Medicine 2018; 178(5):673-678.


The study examined the opioid prescribing rates among Medicaid enrollees in the context of state marijuana liberalization policies between 2011 and 2016. The primary data source for the study was State Drug Utilization Data from the Centers for Medicare and Medicaid Services (CMS).

The authors used data from the first quarter of 2011 through the second quarter of 2016; 2011 was the first year in which state reporting of Medicaid managed care prescription data became mandatory and nearly complete under the Affordable Care Act data collection requirements.

The state-level opioid prescribing rate was measured – that rate was defined as the number of opioid prescriptions that were primarily used for pain management and covered by Medicaid on a quarterly per-1,000-Medicaid-enrollee basis in each state. The state marijuana liberalization policies included the implementation of medical and adult-use marijuana laws from 2011 to 2016.


The implementation of medical marijuana laws was associated with a 5.88% lower rate of Medicaid-covered prescriptions for all opioids. 

The authors also discovered the following about states with some sort of legalized marijuana:

  • Given the annual rate of Medicaid-covered opioid prescriptions is on average 670.16 per 1,000 enrollees in states without marijuana laws, the effect of the medical marijuana laws was equivalent to 39.41 fewer opioid prescriptions per 1,000 enrollees per year.
  • When states with existing medical marijuana laws implemented adult-use marijuana laws, the change was associated with an additional 6.38% lower opioid prescription rate.
  • Using the annual average in states with medical marijuana laws but no adult-use laws, which was 621.82 opioid prescriptions per 1,000 enrollees, the effect of the adult-use laws was translated to 39.67 fewer opioid prescriptions per 1,000 enrollees per year.
  • The lower rate of opioid prescribing associated with adult-use marijuana laws was mainly concentrated in Schedule II opioids, i.e., morphine, meperidine, hydrocodone with acetaminophen, oxycodone.
  • Implementation of adult-use marijuana laws was associated with a 9.78% lower Medicaid spending on prescription opioids, equivalent to an annual saving of $1,815 in Medicaid spending per 1,000 enrollees.
  • Implementation of medical and adult-use marijuana laws was associated with a lower rate of Medicaid-covered prescriptions for nonopioid pain medications of 8.36% and 8.69%, respectively.


Medical and adult-use marijuana laws have the potential to reduce opioid prescribing for Medicaid enrollees, a segment of the population with a disproportionately high risk for chronic pain, opioid use disorder, and opioid overdose. Marijuana liberalization may be one potential aspect of a comprehensive approach to tackle the opioid crisis.

Medicare Part D Study

The objective of the Medicare Part D study was to examine the association between prescribing patterns for opioids in Medicare Part D and the implementation of states’ medical cannabis laws. The authors were from the Department of Public Administration and Policy at the University of Georgia, Athens.

The study can be accessed at: Bradford AC, et al. Association between US state medical cannabis laws and opioid prescribing in the Medicare Part D population.  JAMA Internal Medicine 2018; 178(5):667-672.


The authors analyzed the daily doses of opioids filled in the Medicare Part D plan for all opioids as a group and by U.S. state and by those states with state-level medical cannabis laws from 2010 through 2015. In terms of marijuana laws, separate models were estimated first for whether the state had implemented any medical cannabis laws, and secondly, for whether a state had implemented either a dispensary-based or a home-cultivation-only-based cannabis law.

The primary outcome measure was the total number of daily opioid doses prescribed (in millions) in each U.S. state for all opioids. The secondary analysis examined the association between the medical cannabis law separately by opioid class.

Prescription data were obtained from the Medicare Part D Prescription Drug Event Standard Analytic Files. The public use versions of these data were available under the Freedom of Information Act. The authors compiled the raw prescription drug event data to the physician-drug level each year. They used the total number of daily doses prescribed by each physician.

The variable that was measured was those states that had a medical cannabis law in place. Home cultivation of cannabis is sometimes permitted. At the time of the study, 15 states allowed at least some patients to cultivate a predetermined amount of cannabis at home. Since 2009, every state that had passed a medical cannabis law has included some form of regulated dispensary program. At the time of the study, those states totaled 24 and the District of Columbia.


Medical cannabis laws of any sort were associated with a 2.211 million daily dose decrease in filled prescriptions compared with states that did not have active medical cannabis laws. 

The authors further broke down the data as follows:

  • Mean utilization for any opioid in Medicare Part D between 2010 and 2015 was 23.08 million daily doses per year.
  • Mean annual daily doses for the major subcategories of opioids were:
    • 11,780,00 for hydrocodone
    • 834,000 for oxycodone
    • 1,381,000 fentanyl
    • 1,703,000 for morphine
    • 673,000 for methadone
    • 6,715,000 for all other opioids.
  • When compared with having no medical cannabis law, the authors found that permitting access via a dispensary was significantly associated with a decrease in prescribing of 3.742 million daily doses (or 14.4 % decrease) annually.
  • Access via home cultivation only was associated with a decrease of 1.792 million annual daily doses (or 6.9% decrease).
  • Statistically significant decreases were observed for hydrocodone and morphine:
    • Hydrocodone use decreased by 2.320 million daily doses filled (17.4% decrease) in states with dispensary-based medical cannabis laws and decreased by 1.256 million daily doses filled (9.4% decrease) in states with home-cultivation-only-based medical cannabis laws. 
    • Morphine use decreased by 0.361 million daily doses filled (20.7% decrease) in states with dispensary-based medical cannabis laws.
    • Associations between dispensary-based medical cannabis laws and fentanyl and other opioid use were not statistically significant but trended in the same direction as with hydrocodone and morphine.


An accompanying article by Hill and Saxon (JAMA Internal Medicine 2018; 178(5):679-680) commented on the two studies: Firstly, that both medical and recreational cannabis laws were associated with annual reductions in opioid prescribing rates, and secondly, that cannabis legalization may play a beneficial role in the opioid crisis. 

Hill and Saxon further stated that the results dovetail with preclinical research showing that cannabinoid and opioid receptor systems mediate common signaling pathways central to clinical issues of tolerance, dependence, and addiction. This supports anecdotal evidence from patients who describe a decreased need for opioids to treat chronic pain after initiation of medical cannabis therapy. Both published studies provide evidence suggesting that implementation of medical and recreational cannabis policies may be associated with reduced opioid use and mortality.

Further research is needed to support the concept of cannabis as a tool that can be used to diminish the harm of prescription opioids.

Richard L. Wynn, BS Pharm, PhD, is professor of pharmacology at the Baltimore College of Dental Surgery, Dental School, University of Maryland Baltimore.

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