Monday, June 10, 2019

Medical Cannabis Does Not Prevent Opioid Overdoses

The political aspects of medical cannabis are undeniable. The legalization of cannabis for recreational purposes had no traction with American politicians or voters until it was promoted as a miracle drug.  With that widespread promotion medical cannabis is now legal in 33 states and recreational cannabis is legal in ten.  The legalization arguments also suggested that the US was behind other countries of the world when there are only two countries – Canada and Uruguay – where it is completely legal for medical or recreational sale and purchase.  In the world, 22 of 195 countries have legalized medical cannabis with widely varying restrictions on its use. The Netherlands is often cited as an example of recreational cannabis use, but most Americans don’t realize that it is illegal for recreational use and tolerated for use and sale only in specially licensed coffee shops.  The promotion of cannabis as a solution to the opioid overuse and chronic pain problems can be seen as an extension of the political arguments for legalization that outpace any science to back them up.

There was probably no greater hype about the purported benefits of medical cannabis than early data suggesting that it might decrease the rate of opioid overdoses (1). The sequence of events was supposed to be opioid users tapering off of opioids or using lower equivalent amounts because of medical cannabis use.  The original study covered the time period from 1999-2010 and suggested that states with medical cannabis laws had a lower mean opioid overdose mortality and that the annual rates of overdose progressively decreased over time.  The authors conclusion was:  “Medical cannabis laws are associated with significantly lower state-level opioid overdose mortality rates.”

Despite the usual caveats suggested by the authors in the original study the results of that study were heavily hyped by all cannabis promoters as was the discussion of many Internet forums.  The lay press, public, and politicians saw it as another reason to promote medical cannabis and recreational cannabis by association.

A study came out today in PNAS (2), that is an extension of the original data and it no longer comes to the same conclusion.  In this new study the authors replicated the opioid mortality estimates from the original study but when the data was extended from 2010 to 2017 – the improved opioid overdose mortality rates not only did not stay constant but they reversed themselves to that they were now on the average from -21% to +23%.  They provide an even more valuable analysis of this effect as spurious rather than a true positive or negative effect based on the low penetration of medical cannabis in the population at large (2.5%).  The authors focus on the problem of ecological fallacy – that is conclusions about individuals are drawn from aggregate data across the entire population.They point out that the states with the medical cannabis laws have a number of characteristics separating them from other states.  A recent good example of this fallacy was the New England Journal of Medicine (3,4) report that per capita chocolate consumption correlated with the number of Nobel Laureates in a particular country.  

This is a valuable lesson in scientific analysis. The political approach to the problem is all that most of the public sees. That approach is to grab any information that seems to agree with your viewpoint and run with it.  Big Cannabis and cannabis promoters have been doing this for almost 20 years now. The process of science on the other hand is slower and more deliberate.  It is not a question of a right answer but a dialogue that hopefully produces the right pathway. The authors of this study have added a lot to the dialogue about cannabis but also statistics and how statistical descriptions may not be what they seem to be. 

George Dawson, MD, DFAPA


1: Bachhuber MA, Saloner B, Cunningham CO, Barry CL. Medical Cannabis Laws and Opioid Analgesic Overdose Mortality in the United States, 1999-2010. JAMA Intern Med. 2014;174(10):1668–1673. doi:10.1001/jamainternmed.2014.4005 (full text)

2:  Shover CL, Davis CS, Gordon SC, Humphreys K.    Association between medical cannabis laws and opioid overdose mortality has reversed over time.  First published June 10, 2019  (full text)

3: Messerli FH. Chocolate consumption, cognitive function, and Nobel laureates. NEngl J Med. 2012 Oct 18;367(16):1562-4. doi: 10.1056/NEJMon1211064. Epub 2012 Oct 10. PubMed PMID: 23050509.

4:  Pierre Maurage, Alexandre Heeren, Mauro Pesenti, Does Chocolate Consumption Really Boost Nobel Award Chances? The Peril of Over-Interpreting Correlations in Health Studies, The Journal of Nutrition, Volume 143, Issue 6, June 2013, Pages 931–933,


Above figure is from the original article (reference 2): "This open access article is distributed under Creative Commons Attribution-Non Commercial No Derivatives License 4.0 (CC BY-NC-ND).y"  See this link for full conditions of this license.


  1. "Big cannabis"

    That made me laugh.

    Things have really come full circle. The Big Lebowski has replaced Big Tobacco.

    I wonder if, in the words of Don Henley, the CEOs have a Deadhead sticker on their Cadillac. Probably an Esplanade.

    Here in totally sane and completely enlightened all-about-the science-California, the geriatric Deadheads are enthusiastically pro-pot while in a hysterical tizzy about the popularity of vaping.

    They really need to ban sale of edibles and ban use of pot if you're under 25. It should be banned on all college campuses. And I'm pro-legalization. This will not happen in California where there are needles all over the place despite pot legalization. Dudeism is the official state religion.

    1. As an investor I have been tracking weed for a while. I predicted many years ago that Big Tobacco and Pharma were already researching it and that it would not surprise me if they had plant tissue culture operations and medicinal chemists working on products and waiting for the wholesale legalization and financial legitimization.

      A few signs of Big Cannabis" include:

      The Canada Cannabis Spot Index (CCSI) tracks the AWP of cannabis (currently $7.79/gram).

      OTCCQX - cannabis index that tracks 56 related Canadian cannabis stcoks

      ETFMG (Alternate Harvest ETF) aka NYSEARCA: MJ - first US ETF to track "the cannabis/marijuana industry".

      There is probably more evidence. I was considering speculating in this area but then realized this is currently just a commodity getting cheaper by the minute and the average user wants to grow their own. When people realize how cheap it will be, it will probably be as profitable as a liquor store and have the same pricing dynamics (30 progressively cheaper brands of vodka).

      I will stick to high tech and avoid needing to disclose a losing investment in weed.

  2. Also they have competition from criminals:

    That was another campaign would reduce crime.

    1. In that campaign discussion they never disclose that there are still illicit markets in both alcohol and tobacco. That's why we have an ATF. WHO estimated that at least 10-15% of the alcohol consumption in the countries they researched was consumed from illegal sources.

      I think the cannabis problem is even worse in Colorado. I heard their cannabis czar speak at one of our district branch meetings. He had detailed information on the subject and said he would send it to us on request. I requested and did not get any details back. There is a web site that tracks interstate police stops of cannabis shipments - but you have to be the police to log in and look at that traffic.

      I think the price will have to drop a lot lower than $7.80 a gram before illegal sources lose interest.

      So much for the legalization theory getting rid of the criminal element.