Medical Marijuana Against Opioid Abuse: New Study Challenges Link

In the United States, federal law has severely limited our ability to study all the potential medical properties of cannabis. But, given some limited studies and many anecdotes, a number of states have decided to legalize marijuana for medical purposes. This has allowed some population-level studies of what is happening in the states, but they have faced additional complications, such as different rules from one state to the next and legalization in progress. recreational use disturbing the picture.

Last week, the publication of an article suggesting that one of the biggest successes of marijuana for medical purposes was illusory made all this confusing. Some initial studies indicated that states that had legalized marijuana use for medical purposes experienced a decline in opioid-related deaths. The new research replicates these results, but notes that the trend has reversed in recent years, with states currently recording an increase in deaths. Although the authors of the new study suggest that the initial findings were false, others suggest that the changing legal landscape and changes in substance abuse may have resulted in this change.

What is everyone on the agreement?

In 2014, researchers compared deaths due to opioid abuse in states with and without legalization of marijuana for medical purposes. Prior to 2010, the trend was clear: States that licensed marijuana for medical purposes had lower rates of opioid abuse deaths.

Although it was a correlation study that did not identify causal mechanisms, it was not too difficult to find a plausible explanation: one of the uses of marijuana for medical purposes was the treatment of intense pain, the same thing that opioids are used to treat. The substitution of marijuana for these analgesics is an obvious mechanism that could potentially explain the correlation. As subsequent studies have confirmed this trend, the findings have been used in ongoing policy debates on appropriate policies for marijuana use.

This paved the way for the new study, which uses data from previous work, but extends its scope to years up to and including 2017. Instead of a 20% drop, the study reveals a increase Deaths from opioid abuse in states that have legalized marijuana for medical purposes.

Superficially, this may seem like another large-scale case study that does not happen again. In fact, the authors note that if they cut data to 2010, they could replicate the results of the previous study. It is simply that, from around 2005, the trend of the correlation stabilized and then increased sharply around 2012. The changes prior to 2010 were too brief and less important to have a significant impact on the observed trend. in the longer dataset; those after 2012 were simply unavailable in the first study.

So everyone agrees that the initial trend was real and the analysis that revealed the most recent trend is scientifically valid. Where people differ, it is in the interpretation.

A fake connection?

So, what are the possibilities that could explain why a correlation would disappear over time? The simplest explanation, and the one advocated by the new articles, is that the correlation was wrong at first. Things lined up for a short time but eventually diverged because they were not related to each other.

The paper advances a number of arguments in favor of the falsity of the connection. It notes that cannabis users for medical purposes represent only 2.5% of the total population, which raises the question of whether they can have a significant effect on trends at the scale of the society. But they also downplayed this argument by noting that a separate study of medical cannabis had revealed that its users were more likely to consume and abuse prescription painkillers. This suggests that medical cannabis is more likely to influence trends in the population at risk of opioid overdose.

In the opinion of the authors of the paper, however, the link between medical marijuana use and analgesic consumption is inconsistent with the former limiting the latter. They add that there is no clear link between the number of opioid overdose deaths and the severity of the marijuana laws, which can range from strict limits to the types of cannabis available in Canada. medical purposes for recreational use. For the time being, however, the most extreme policies have been in place only recently and in a limited number of states. Therefore, their separate analysis leads to enormous statistical uncertainty. As such, it is really impossible to say anything about the effects of policy rigor.

But what did we learn from each other?

To get an additional perspective on this issue, we talked to one of the authors of the first article describing the correlation between marijuana for medical purposes and opioids. Chinazo Cunningham practices internal medicine, including drug treatment, at the Albert Einstein College of Medicine. It argued that the initial reasons for believing that the correlation could be significant are still valid and have been supported by additional data in the meantime. "Randomized clinical trials show that cannabis reduces pain in humans," Cunningham told Ars. "And we also have several studies that have shown that states that have medical cannabis have reduced opioid prescribing.We also know that patients report taking fewer opioids to relieve their pain when they are inactive." they consume cannabis. "

(While we were preparing this coverage, another document was published showing that marijuana laws for medical purposes are associated with a reduction in opioid prescriptions.) But it was found that marijuana laws at recreational purposes were not and the effects were specific to those younger than 55 years old.)

While this does not mean that the correlation is an indication of a real connection, Cunningham suggested that they are sufficient for it to be worth considering. And, if there was a link, it suggests that something had to change to decouple the two.

Cunningham had some ideas on what could explain this change. One is a change in the cause of overdose deaths from opioids. The increase in the number of deaths due to prescription opioids has stabilized around 2010, when the initial study was running out of data, and has remained virtually unchanged ever since. In contrast, heroin deaths began to increase dramatically at about the same time, resulting in an even faster increase in the number of deaths from synthetic opioids such as fentanyl, which began in 2015. It is possible that the shift in focus from prescription drugs to illicit drugs, or the high potency of fentanyl, has changed the relationship with marijuana that is supposed to be used for medical purposes.

Cunningham noted another potential confusing influence, namely that there may have been a population change due to states that have legalized cannabis for medical purposes since 2010. "We know that states with The highest opioid overdose deaths in Ohio, West Virginia and Pennsylvania have recently legalized medical cannabis, "she said. This does not mean that the initial correlation was definitively informative; rather, it suggests that we should not dismiss information as false without taking a closer look at these additional factors.

But the possible factors mentioned by Cunningham indicate that it will be difficult to understand everything. "There are a host of other things going on at the same time [that changes in] policies on medical cannabis are also being applied, "she said, as researchers try to track the evolution of drug abuse, the drugs consumed are changing, states that allow cannabis for medical purposes are changing. and the availability of cannabis is changing rapidly.

And Cunningham, along with the authors of the new paper, points out that all we can do for the moment is to track the correlation. "We need to do the studies to determine causality – the randomized controlled trial, and to do that, the federal government needs to change its policy," she told Ars, citing limitations on studies of marijuana. "Until that happens, we will all have to guess, or it will be a little bit of an act of faith as the states continue to move in. And really, it's terrible. Our policies should be guided by Science."

PNAS, 2019. DOI: 10.1073 / pnas.1903434116 (About the DOIs).