UW ADAI - Symposium - 2024 - Reviewing the Evidence
(September 19, 2024) - Daniel Myran

2024-09-19 - UW ADAI - Symposium - 2024 - Reviewing the Evidence - Daniel Myran - Takeaways
[ Event Details ]

A researcher from the University of Ottawa in Canada discussed his country’s experience with legalization, including health studies he’d participated in, and addressed a couple of questions.

Here are some observations from the Thursday September 19th University of Washington Addictions, Drug, and Alcohol Institute (UW ADAI) Symposium titled, “Cannabis, Schizophrenia, and Other Psychotic Disorders: Moving Away from Reefer Madness Toward Science."

My top 4 takeaways:

  • Myran started by contextualizing Canadian legalization in 2018 and the resulting regulatory landscape which was significantly controlled at the provincial level (audio - 27m, video - UW ADAI, presentation).
    • Myran explained the policy framework used for 2018 legalization of adult use cannabis in Canada was designed to achieve "strict legal regulation.” He shared a chart illustrating “two spectrums of drug policy, where you move from total prohibition on the left to commercialization or commercial promotion on the right.” Myran elaborated that “the thought is, is that when you have total prohibition, you have an unregulated illicit market with a high degree of criminal justice harms and other health harms, and that if you get into the sweet spot of strict legal regulation, you can minimize those criminal justice harms and those health harms.”
    • However, “if you move too much into the area of an unregulated legal market with promotion and widespread commercial and for-profit motive,” public health risks from increased use become more pronounced, he noted. Moreover, Myran argued that the Canadian framework aimed to treat cannabis similarly to alcohol and tobacco, which "is insufficiently regulated" in Canada and many “high-income countries.” He’d seen the lawful cannabis market expand rapidly after legalization, and asserted self-reported surveys showed increases in cannabis use. Myran showed a chart illustrating total spending on cannabis in Canada from 2010 to 2022, including estimates on illicit sales, legal non-medical sales, and medical cannabis indicating “the legal market has expanded twice as fast as the estimated illicit market has contracted.” He stated that by 2022, self-reported cannabis spending had "increased 40%" from the start of legalization.
    • Myran’s presentation covered survey data showing that by 2023, “the number of adults who are reporting past year cannabis use is almost tripled relative to the number of people in 2010," and "a quarter to 40% of people in Canada who consume cannabis consume it daily, or near daily.” He was also troubled by the increased level of tetrahydrocannabinol (THC) in cannabis products sold legally in Canada. Myran showed data from a 2017 study in the New England Journal of Medicine tracking THC levels in cannabis seizures, which rose "from around 4% in 1995 to just under 12% in 2012,” when cannabis was first legalized in Washington and Colorado, adding "for context, what we're currently selling legally in Canada, almost all the products are in excess of…20% THC.”
    • Sales data for cannabis flower from the Ontario Cannabis Store (OCS), Ontario's government-run retailer, reflected that in 2022, "71% of all dried flower has more than 20% THC" sold through OCS, and if CBD-dominant strains are excluded, the figure rises to "93% [of flower sold was over] 20% THC.” He pointed out "the opening website of our government cannabis retailer" promoted "best-selling ounces" of flower withTHC levels "greater than 24%.”
  • Myran delved into his specific research on healthcare visits, correlation between cannabis use and schizophrenia, and another article on criminal justice data.
    • Myran described his first study using population-level data to analyze rates of emergency room (ER) visits and hospitalizations related to cannabis use in Canada between January 2016 and May 2021.
      • Because Canada has a universal healthcare system that covers 97% of residents, researchers had access to health care visit data for almost all Canadians, he explained, and could "specifically identify healthcare visits that are due to cannabis or related to cannabis" from diagnostic codes, plus "the clinical judgment of the team caring for that person.” When looking at ER visits and hospitalizations for "overall reasons due to cannabis,” their definition encompassed intoxication, poisoning, withdrawal and "a wide range of different conditions.”
      • “The rate of these visits has gone up enormously over time, very much in line with increasing cannabis potency and the number of people who are using cannabis,” remarked Myran. He said, "the largest increase has been for visits for cannabis-induced psychosis" during the study period.
        • Yale University School of Medicine Psychiatry Professor Deepak Cyril D’Souza, another panelist, spoke about how researchers used cannabis-induced psychosis as a diagnostic term.
    • Myran reviewed his second longitudinal study of population-level data, which focused on cannabis-related emergency room visits and the subsequent development of psychotic disorders and schizophrenia.
      • The study looked at individuals aged 14 to 65 who had never been treated for psychosis or schizophrenia, and who had at least one "first time visit for substance use.” Myran described how among individuals who had an ER visit for cannabis-induced psychosis, "26% of people will be diagnosed...will have a new diagnosis of schizophrenia, within three years.” By comparison, Myran explained the risk of developing schizophrenia in the general population during the same period was around 0.1%.
      • He explained that even among individuals who went to the ER for "cannabis use with intoxication or cannabis poisoning" but who did not have psychosis, "there still is a quite large elevation in the risk of schizophrenia" at almost 2% within three years. Myran described “a gradual increase over time" in the rate of these disorders, but "during the initial period after legalization, during the restricted market, there isn't really much of a change.”
      • Myran then examined national data from Canada on the incidence of schizophrenia hospitalizations for people aged 15 to 19 and 20 to 24, broken down by sex. His research found “the incidence of hospitalizations for schizophrenia have been rising over the study period," with a pronounced "jump that occurs...in 2021 and 2022 which is again, during the period of the COVID-19 pandemic, and when the legal markets are taking off in Canada.”
      • While acknowledging these trends don't necessarily show "that increasing cannabis use is changing the incidence of schizophrenia,” Myran clarified that "we should look at data like this with some caution" and that "further study is needed.” He stressed that because "the average time between first cannabis use and diagnosis of schizophrenia is around six years,” it was "too soon" to assess the impact of legalization on schizophrenia rates. Myran also recognized the difficulty of establishing causality between cannabis use and the risk of psychotic disorders due to confounding factors. He noted that "these are not causal studies" because the researchers had "no control over all sorts of confounders, including genetics.”
    • Myran described how Canadian legalization led to a decrease in criminal justice involvement for cannabis offenses, but questioned whether the same benefit could have been achieved through decriminalization, without a comparable increase in public health harms. Delving into data on cannabis arrest rates in Canada from 2010 to 2023, Myran noted "they were going down... Starting in 2011 they've been decreasing, and most of the decrease actually occurs in the lead up to legalization.”
    • Myran stated that legalizing cannabis in Canada "did not seem to accelerate increases in adult cannabis use harms", but that "there was a very strong trend of increasing harms and use in the lead up to legalization" that might have been driven by the expansion of the medical cannabis market and shifting social norms. He considered there to be no need to "sell cannabis infused gummies, or... sell cannabis chocolate with sprinkles on it, or have products with fluorescent promotion" to reduce cannabis-related arrests. Myran concluded that policymakers needed to "have a more nuanced conversation" around legalizing and/or commercializing cannabis, as some benefits of legalization might be achieved through decriminalization, without creating a commercial market.
    • Additional government publications, research, and media reporting on the impacts of cannabis legalization in Canada:
  • In the question and answer session following the panel, Myran replied to inquiries about the pesticides on cannabis, differences in use data based on sex, and the complexities around creating an effective, strict regulatory regime.
    • WSLCB Research Program Manager Sarah Okey asked if researchers had looked into "whether there's any relationship between the potency of cannabis and exposure to things like pesticides, fungicides" that could be confounding factors (audio - 2m, Video - UW ADAI).
      • Myran responded that "there's a lot of debate about the extent to which" differences in pesticide and fungicide exposure between high- and low-potency cannabis products "would confound the results.” 
      • D’Souza, suggested cannabis was "a component cause similar to cigarette smoking and lung cancer,” and that it "may interact with other factors, factors that we don't fully understand.”
    • Okey brought up Myran’s data on cannabis use disorder and cannabis-induced psychosis visits in Canada, asking him to speak about how it “showed differences between males and females" (audio - 1m, video - UW ADAI).
      • Myran replied that “it's nuanced and depends on the policy period, but in general, there were larger increases for females than males during the commercialization period.” He then said how “episodes of cannabis-induced psychosis [were] very hard to tease out…because of the overlap with the COVID-19 pandemic during that data period.” Myran suspected that “as more and more consumers come into a legal market, it could be…you have differential access to new products and patterns of use…for males and females.”
    • Okey regarded Myran's "discussion on policy changes and impacts with emergency department visits and healthcare visits [as] so timely in the US right now" since more states had legalized cannabis. She asked him to elaborate on "effective policy interventions" to mitigate cannabis-related harms (audio - 12m, video - UW ADAI).
      • Myran responded that the "evidence base for cannabis is growing, but is still early" and that policymakers could draw on the larger body of research on alcohol and tobacco when making policy decisions. He advised setting "higher minimum legal ages of purchase,” given that “some early data from Canada [showed] the higher you set it, the more protective effects there are,” and noted that U.S. states’ age limits were already higher than Canada, which had “gone to 18 in one of our provinces, and 19 for most of the rest of the country.”
      • He further called for using "financial levers" like taxation to “reduce the use of higher potency products,” and limiting or prohibiting the sale of cannabis edibles and vapor products.
      • “I see Quebec…has taken a very different approach for much of the rest of the country for legalization,” Myran observed. He indicated they didn’t allow edibles or vapor products to come to market and placed “limits on the potency of THC.” Along with the revenue the provincial government collected through the Société Québécoise du Cannabis (SQDC), “their experience so far has been that they have avoided some of the increases in cannabis use and harms that have occurred in other jurisdictions,” Myran stated.
      • Myran pointed out that "when we talk about legalization, it's often presented as a binary yes/no,” but legalization was really a "very complicated set of different regulatory choices” that included "real differences in implementation.”
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