Medical cannabis is not a solution to the opioid crisis

Contrary to previous researches and preconceived ideas, the legalization of cannabis for medical purposes and the wider access to it have not made it possible to reduce the rates of opioid overdose deaths.

A study done at Stanford University in California has shown no protective effect of medical cannabis. In fact, states that legalized medical cannabis reported a 22.7% increase in the number of opioid overdose deaths.

"People and the cannabis industry have been touted by the idea that the adoption of a cannabis law was a way to achieve this," explained the ###################################################################################### 39 author Chelsea L. Shover, PhD, epidemiologist and postdoctoral fellow in psychiatry. , Stanford University School of Medicine in Palo Alto, California, said Medscape Medical News.

"The important point to note from our study is that medical cannabis laws do not seem to reduce opioid overdoses at the population level, but that does not mean we should not continue our research and carry out political discussions on cannabis laws, "she said. I said.

The results were published online on June 10 in Proceedings of the National Academy of Sciences.

"Sensational" findings

An earlier study published in JAMA Internal Medicine in 2014 showed that from 1999 to 2010, states with cannabis laws for medical purposes experienced a slower increase in the number of opioid overdose deaths. This study analyzed the period from 1999 to 2017.

The first study "caused a stir by showing that national laws on medical cannabis were associated with lower than expected opioid overdose mortality rates from 1999 to 2010," the authors write.

The enthusiasm for this approach was expressed "despite the reservations of the [original study] authors and others to be cautious when using ecological correlations to draw causal conclusions at the individual level, "note the researchers.

Between the conclusion of the previous study and the closing date of this study (2010 – 2017), 32 states have enacted medical cannabis laws, 17 of which authorize medical cannabis containing low levels of tetrahydrocannabinol (THC, the psychoactive compound of cannabis), and 8 states have enacted cannabis laws for recreational purposes.

Nevertheless, the number of opioid overdose deaths has increased significantly over this period.

The researchers wanted to return to the question using the same methods as those used in the initial study, but by extending the period of 7 years.

In addition, they created a model that took into account the presence of cannabis laws for recreational use, which presumably presupposes better access to cannabis or a restriction of low THC content, which explains a more limited access.

Therefore, if broader access to cannabis rather than medical cannabis is associated with lower opioid overdose mortality, "we would expect to see the most negative association between the states. with the least negative (or even positive) laws on recreation and association in low-THC-only states, "the authors note.

Compose the problem?

The authors reanalyzed the period 1999-2010 and obtained similar estimates to those of the initial study.

However, they also found slight differences that were likely due to missing values ​​from 30 State / Year combinations – for example, previous study investigators estimated a 24.8% reduction in the number of deaths per 100,000 locals associated with the introduction of a law on cannabis for medical purposes, while researchers in this study have estimated a decrease "statistically indistinct" of 21.1%.

Also following the findings of the original model, Shover and colleagues found that none of the four time-varying covariates, including the annual unemployment rate in the state and the presence of a prescription drug monitoring program, Laws on the supervision of pain treatment centers and laws requiring or allowing pharmacists to seek identification, were significantly associated with opioid overdose mortality.

On the other hand, the data from 1999 to 2017 revealed that the trend in cannabis laws for medical purposes was reversed: States adopting a law on cannabis for medical purposes recorded an increase of 22.7 % (95% confidence interval, 2.0, 47.6) of overdose deaths.

Their additional robustness test allowed estimating models with linear state-specific temporal trends, as well as fixed state and year effects.

The results of this analysis also showed that the "sign of the effect of cannabis law for medical purposes has shifted from negative to positive once the data expands until 2017", although the Magnitude was "diminished" and that the estimate was not found to be statistically significant in either case. specification.

For the final dates between 2008 and 2012, the association was negative; however, the association became statistically indistinguishable from scratch and then became positive in 2017.

The expanded model included indicators for different types of cannabis laws and showed that having a global law on medical cannabis was associated with a higher opioid overdose mortality of 28.2% (1,2, 62.4), while estimates for other laws were insignificant.

The association between a recreational cannabis law and opioid overdose mortality was -14.7% (-43.6, 29.0), while the association between a cannabis law for recreational purposes and opioid overdose mortality was -14.7% (-43.6, 29.0), while the association with a low THC cannabis law was -7.1% (-29.1, 21.7).

"If the evaluation criterion had been between 2008 and 2012, the results would have been comparable to those obtained by Bachhuber et al," note the authors.

"However, the association became ambiguous in 2013 [and] by 2017, the situation had reversed, so a study conducted this year could lead some to conclude that cannabis laws for medical purposes exacerbate opioid overdose mortality, "he added. they.

What works, what does not work

Shover distinguished two questions about the relationship between opioids and medical cannabis.

"We wanted to know if cannabis could be a potential solution to the opioid crisis and overdose mortality and we found that this was not the case at the population level."

The second question "is whether [cannabis] is an effective pain relief for some people, which is an important issue that hopefully will allow more people to get to the bottom of things. "

The separation of these issues was the "main contribution of this study," said Shover.

"On the one hand, we want to avoid deaths from overdoses and we do not spend more time on strategies that do not work, but we do not spend more on finding strategies that work or developing those that we already know. "

An important intervention is to reform the incarceration "because, just after his release from prison, people are particularly vulnerable to overdose because they have not used it [opioids] in prison and when they are released, they use the same amount that they had used before incarceration and they overdose, "she said.

A better way to prevent overdose of opioids is to increase access to naloxone, "which we know works."

It is also important to "facilitate access to treatments for opioid use disorders, including drugs such as suboxone, methadone and naltrexone as well as non-pharmacological treatments," Shover observed. .

Making treatments more available, de-stigmatizing treatments and providing "solid coverage" for treatment are essential elements for treating opioid overdoses.

"We have a lot of evidence about what works, so the challenge is to have the political will and support of the health system to make it accessible to people," she said.

Controversial Policy Areas

Commenting on the study for Medscape Medical NewsDan Berlau, PhD, an associate professor of pharmaceutical science at the Regis University School of Pharmacy in Denver, Colorado, said the findings compel "scientists to reassess their assumptions about cannabis and opioids."

Much more research "needs to be conducted specifically on causal relationships and individual patient analyzes" because "the ecological sophistry described here is a very real phenomenon," said Berlau, who did not participate in the study. # 39; study.

The study "further highlights the need for federally funded cannabis research, which is currently very limited and extremely difficult to achieve," he noted.

"Once real tangible benefits or cannabis can be established (or excluded), clinicians can then properly educate their patients," he added.

"The non-robustness of the previous results also highlights the challenges of controlling scientific messages in controversial policy areas," the authors note.

"Business actors (for example, the medical cannabis industry) with deep pockets have a substantial capacity to promote positive outcomes, and people who suffer are desperate for effective solutions," he said. they.

Indeed, cannabinoids have "proven therapeutic benefits, but the reduction in opioid overdose mortality at the population level does not appear to be part of it," they conclude.

Shover has benefited from the support of the National Institute for Combating Drug Abuse of the National Institutes of Health and the Wu Tsai Neuroscience Institute. Sources of support from other authors were listed on the original document. Berlau has not disclosed any relevant financial relationship.

PNAS. Posted online June 10, 2019. Summary

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