Does marijuana use reduce or increase opioid consumption?

Why there's more to scientific research than just the headline

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Marijuana and Opioids: Scientific Research

A new study published by Theodore L. Caputi and Keith Humphreys in the Journal of Addiction Medicine reports that medical marijuana users are "more likely to use and misuse other prescription drugs." This analysis compliments another study authored earlier this year by Mark Olfson in the American Journal of Psychiatry which concluded:

"Cannabis use appears to increase rather than decrease the risk of developing nonmedical prescription opioid use and opioid use disorder."

That's right - these studies assert that medical marijuana may actually increase the risk of prescription drug use.

Such conclusions fly in the face of a number of other studies published recently that have found that the implementation of medical marijuana policies may actually curb opioid use. Here's a few examples:

• “Association of Medical and Adult-Use Marijuana Laws With Opioid Prescribing for Medicaid Enrollees”, Hefei Wen, PhD; Jason M. Hockenberry, PhD:

“In this population-based, cross-sectional study using the all-capture Medicaid prescription data for 2011 to 2016, medical marijuana laws and adult-use marijuana laws were associated with lower opioid prescribing rates (5.88% and 6.38% lower, respectively)...Medical and adult-use marijuana laws have the potential to lower opioid prescribing for Medicaid enrollees, a high-risk population for chronic pain, opioid use disorder, and opioid overdose, and marijuana liberalization may serve as a component of a comprehensive package to tackle the opioid epidemic."

• “Medical Marijuana Laws Reduce Prescription Medication Use In Medicare Part D”, Ashley C. Bradford and W. David Bradford

"Using data on all prescriptions filled by Medicare Part D enrollees from 2010 to 2013, we found that the use of prescription drugs for which marijuana could serve as a clinical alternative fell significantly, once a medical marijuana law was implemented. National overall reductions in Medicare program and enrollee spending when states implemented medical marijuana laws were estimated to be $165.2 million per year in 2013...The availability of medical marijuana has a significant effect on prescribing patterns and spending in Medicare Part D.”

• “Cannabis as a Substitute for Opioid-Based Pain Medication: Patient Self-Report”; Amanda Reiman, Mark Welty , and Perry Solomon

"Respondents overwhelmingly reported that cannabis provided relief on par with their other medications, but without the unwanted side effects. Ninety-seven percent of the sample “strongly agreed/agreed” that they are able to decrease the amount of opiates they consume when they also use cannabis, and 81% “strongly agreed/agreed” that taking cannabis by itself was more effective at treating their condition than taking cannabis with opioids...Future research should track clinical outcomes where cannabis is offered as a viable substitute for pain treatment and examine the outcomes of using cannabis as a medication assisted treatment for opioid dependence.”

• “Associations between medical cannabis and prescription opioid use in chronic pain patients: A preliminary cohort study”; Jacob M.Vigil , Sarah S. Stith, Ian M. Adams, Anthony P. Reeve

"Survey responses indicated improvements in pain reduction, quality of life, social life, activity levels, and concentration, and few side effects from using cannabis one year after enrollment in the Medical Cannabis Program (MCP). The clinically and statistically significant evidence of an association between MCP enrollment and opioid prescription cessation and reductions and improved. quality of life warrants further investigations on cannabis as a potential alternative to prescription opioids for treating chronic pain."

• “Association Between US State Medical Cannabis Laws and Opioid Prescribing in the Medicare Part D Population”; Ashley C. Bradford, BA; W. David Bradford, PhD; Amanda Abraham, PhD; et al

"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...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."

• “Medical Cannabis Use Is Associated With Decreased Opiate Medication Use in a Retrospective Cross-Sectional Survey of Patients With Chronic Pain”; Kevin F.Boehnke, Evangelos Litinas, Daniel J.Clauw

"This article suggests that using medical cannabis for chronic pain (CP) treatment may benefit some CP patients. The reported improvement in quality of life, better side effect profile, and decreased opioid use should be confirmed by rigorous, longitudinal studies that also assess how CP patients use medical cannabis for pain management."

So what's to make of these "conflicting" conclusions?

Perhaps the conclusions and supporting data are not actually conflicting. Perhaps the headline is just slightly misleading and one needs to consider the context in which the experiments were conducted.

Caputi and Humphreys indicate that people who report consuming medical cannabis are more likely to also report any use of prescription drugs (medical or non-medical) compared to people who do not smoke medical cannabis.

However, a commentary that accompanies the paper notes that the level of prescription drug use in people may remain relatively high even if medical cannabis leads to reductions in prescription drug use.

Consider the following two people:

• Person 1: has severe chronic pain and began using medical cannabis after initially taking a high-dose opioid in addition to other analgesics (prescribed and unprescribed)
• Person 2: does not take medical cannabis; healthy and does not have chronic pain

Person 1's prescription drug use is obviously much higher than Person 2's. But this doesn't necessarily mean that medical cannabis caused Person 1 to use prescription drugs. Person 1 may even decrease his or her prescription drug use after starting a medical marijuana program, but would still use more prescription drugs than Person 2. The primary driver of the association between prescription drug use and medical marijuana in this hypothetical example is really Person 1's severe chronic pain!

Furthermore, the population of those who consume medical marijuana is skewed with individuals like Person 1 - individuals that seek medical marijuana to palliate severe chronic pain and other associated ailments. Although all medical marijuana patients do not seek treatments for chronic pain, a much greater proportion do so than is constituted in the general population:

"Even if we compare people who take medical cannabis with a sample of people selected from the general population that accesses health care and takes any prescription drug (as in Caputi and Humphreys’ subgroup analysis), prescription drug use may still be higher among people who take medical cannabis because they are still more likely to have severe chronic pain.

The authors of the commentary also offer several other key points to consider:

1. Taking a snapshot at any single point in time is not as useful as a longintudinal study that tracks individuals over time, because it does not provide as much detail on cause and effect.
2. Comparisons of patients with different underlying conditions cannot truly explain the influence of medical marijuana on prescription drug use, because the treatments are necessitated by the underlying conditions. For example, certain underlying conditions, like severe chronic pain, may drive medical marijuana or prescription drug use.
3. There may be sub-groups of medical marijuana users with "specific formulations, routes of administration, or delivery devices for medical cannabis that are associated with distinct impacts on patients."

How do we know what research to believe?

First, it's key to delve into the scientific research you are studying - don't just rely on headlines. There are numerous technicalities, nuances and conditions that accompany the methods and datasets that underlie scientific research. Headlines are often broad and designed to grab a reader's attention.

From a scientific and academic perspective, we need to conduct research in a manner that provides more insight into cause and effect over time, as the commentary's authors suggest:

"To fully understand the effect of medical cannabis on the use of other drugs, prospective longitudinal studies randomizing individuals to cannabis versus other treatments are urgently needed."

We often use conclusions from research done at a population or group level (i.e. studies involving Medicare Part D) to make inferences regarding individuals and vice versa. It's thus also important to consider the level at which the data is being gathered.

Although it does appear that marijuana may address the opioid epidemic, we may need to conduct more, improved scientific research on the issue to prevent us from jumping to false or premature conclusions.

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