Legalized Marijuana Reduces Opioid Prescribing

Hefei Wen, PhD

Medical marijuana legalization is cutting heavily into opioid prescription rates.

A new study has reported that states’ implementation of medical and adult-use marijuana laws is associated with an approximate 6% reduction in opioid prescribing. The results lead researchers to further believe that comprehensive marijuana legalization would serve to combat the opioid epidemic.

Led by Hefei Wen, PhD, assistant professor, Department of Health Management & Policy, University of Kentucky College of Public Health, researchers conducted a cross-sectional study of all Medicaid prescription data from 2011-2016 in states that have begun to implement medical and adult-use marijuana laws during that time period, and states that have not.

Wen told MD Magazine the Medicaid patient population was chosen for analysis due to its evidenced increased risk for chronic pain, opioid addiction, and abuse. A study just last week reported that 82% (95% CI; 80.5 — 83.5) of neonatal abstinence syndrome diagnoses in US infants in 2014 were primarily covered under Medicaid insurance.

Researchers included all Medicaid fee-for-service and managed care enrollees. Aside from targeting the window during which Affordable Care Act (ACA) data collection requirements were first instituted, the chosen time frame minimizes the influence of nationwide guidelines such as the 2010 OxyContin reformulation, guidelines for chronic pain management prescription written before 2011 and after 2016, and other state laws that aligned with guidelines set by the Centers for Disease Control and Prevention (CDC).

Results showed that state implementation of medical marijuana laws was associated with 5.88% lowered rate of opioid prescribing (95% CI; 11.55 — 0.21), while the implementation of adult-use laws was associated with an even lower opioid prescribing rate (6.38% [95% CI; 12.20 – 0.56).

The rate of prescribing for schedule 2 opioids — which include codeine, oxycodone, and fentanyl, among others — dropped 7.79% (95% CI; 14.73 — 0.85) among states with adult-use marijuana laws. For schedule 3-5 opioids — which include anabolic steroids, barbiturates, and cough suppressants with traces of codeine, among others — prescribing was reduced by just 1.36% (95% CI; -12.93 – 10.21) in states with adult-use marijuana laws. However, the rate of prescribing these drugs in states with medical marijuana laws was the most reduced among all groups (10.40% [95% CI; 19.05 – 1.74).

In the overall annual effect size per 1000 Medicaid enrollees, states with medical marijuana laws and adult-use laws saw reductions of 39.41 and 39.67 patients, respectively. Researchers counted these findings as among the first to show recent state marijuana laws have reduced opioid prescribing and spending.

“Most opioid use disorder and overdose cases occurred in patients with legitimate prescriptions from health care professionals for pain management,” researchers wrote. “Marijuana liberalization, therefore, may have benefited these patients by providing them with legal protection and access to marijuana as an alternative relief from their pain conditions.”

Though researchers noted the US population is mostly supportive towards medical marijuana legalization, Wen said 21 remaining states without legalization laws may have regulatory hurdles in their way to providing access. She also noted that issues surrounding pediatric prescription, driving impairment, intoxication, and health-related issues stand in the way of the therapy reaching nationwide clearance.

“We have to consider how to facilitate implementation for the sake of safety,” Wen said.

In an essay accompanying the study, Kevin P. Hill, MD, MHS, of the Division of Addiction Psychiatry at Harvard Medical School, noted distinct disparities between the results of studies such as Wen’s, and those of studies that viewed the association between illicit marijuana and opioid use. He argued that many entities, and even states that tax marijuana, are profiting from the cannabis industry without equally supporting its advancing research. More results as to the effect of marijuana on the opioid epidemic — and its therapeutic benefits overall — require that to change.

“For many reasons, ranging from significant barriers to research on cannabis and cannabinoids to impatience, cannabis policy has raced ahead of cannabis science in the United States,” Hill wrote. “For science to guide policy, funding the aforementioned studies must be a priority at the federal and state level.”

The study, "Association of Medical and Adult-Use Marijuana Laws With Opioid Prescribing for Medicaid Enrollees," was published online in JAMA this week.