It’s no secret that the United States is having some serious issues with narcotic abuse, with a 12.9-fold increase in opioid overdose deaths between 2007–2017. Most of these deaths are attributable to non-prescription narcotics, but it’s widely believed that an increase in opioid prescriptions has led to increased rates of illicit use. As states scramble to find a solution and stem the tide of overdose deaths, many point to what they see as a potential alternative — medical marijuana.
Why look to medical marijuana?
If marijuana were a legal alternative for pain relief, proponents argue, we would see reduced rates of opioid use and fewer overdose deaths. This argument isn’t completely without merit. Fewer opioid prescriptions are written in states where marijuana is legal for either medical or recreational use. Several studies have shown that it is useful as a pain reliever. And while marijuana is addictive, addicts don’t form a physical dependency on the drug, and it’s certainly not as addictive as opioids. Finally, no one has ever died from a marijuana overdose, so on that front it is considerably safer.
That said, these arguments all come with caveats. This is a quote from the article linking marijuana legalization with prescription rates:
“[…]as with any observational study, we cannot definitively establish causality between marijuana liberalization and opioid prescribing.”
In other words, one might have nothing to do with the other. As far as pain relief goes, there is far from a scientific consensus on the subject. Pain is impossible to measure objectively and is highly susceptible to the placebo effect. While a placebo is better than nothing, analgesics like NSAIDS (aspirin and ibuprofen) and opiates work whether you believe in them or not, and are generally stronger in their effect.
Medical marijuana’s proponents were vindicated in 2014 by a paper published in JAMA Internal Medicine, an academic journal affiliated with the American Medical Association. In this paper, the authors found that states with medical marijuana had 24.8% fewer opioid-related deaths than states that didn’t. The article made a big splash in both the scientific and popular press. It’s been cited nearly four-hundred times in the scientific literature, discussed in national and international news outlets, and has spurred new research into the use of marijuana to treat both chronic pain and opioid addiction. Clearly, this was a big win for medical marijuana.
However, new research shows that marijuana may not be the key to solving our opioid epidemic after all. A new article published in Procedings of the National Academy of Sciences re-examined the conclusions of that 2014 paper, replicating the original work and also including data for a longer period of time. Using the new data, they found that states with medical marijuana laws actually had 22.7% higher rates of opioid-related overdose deaths compared to those without.
Who do we listen to?
How can we explain these differing results? It’s tempting to say that one group simply screwed up somewhere, especially if the results of one paper or the other bolsters your pre-existing views. However, this is very unlikely. Both groups were using the same data, which was collected by a third party, the Centers for Disease Control and Prevention. The second group also used the same statistical methods since one of their primary goals was to replicate the first group’s findings. In fact, when they considered opioid overdose deaths for the years between 1999–2010, as the first group did, they got approximately the same result. Therefore, it’s not an issue of the input or the methodology.
The difference comes from the amount of data each group had to draw on. In the first paper, the authors noticed that opioid deaths kept going down each year after the passage of medical marijuana laws. The second group found the same thing… but here’s the kicker: if you keep going, the effect levels off, and then reverses in 2013. In effect, both groups interpreted their results correctly, it’s just that the first group didn’t have enough data to see the fluctuating trends.
Will medical marijuana solve the opioid crisis?
What, if anything, does this tell us about marijuana legalization and the fight against opioid addiction? If there is a connection between the two, it is most likely indirect, and the effect is quite small. These papers did consider a handful of other possible explanations for the observed effect, such as unemployment rates and state laws regarding patient monitoring for opioid abuse, but there are many others that were not included. Further, only ~2.5% of the general population smokes marijuana regularly. Therefore, it’s unlikely that such a small population would account for such a massive swing in the number of opioid deaths.
The simplest explanation is that one does not affect the other. Remember, these studies detect correlations, not causes. Unfortunately, it’s very easy to confuse the two, as often happens when the popular press gets hold of scientific work, and especially on topics as divisive as this one. No doubt we’ll see marijuana’s detractors pointing to this second study as further proof that marijuana is a “gateway drug” that is worsening the opioid crisis. This is an example of why we can’t make policy or personal decisions based on single studies, tempting though it may be. The only way forward is more research and careful journalism.
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About the author:
J. Brandon Lowry holds a PhD from the Institute of Molecular Biology at the University of Oregon. A digital nomad and freelance writer, he writes about cannabis, science, health, and travel. He is also assistant editor at Midnight Mosaic Fiction.