From the Editor

On Oct. 17, 2018, the government of Canada will launch a national, uncontrolled experiment in which the profits of cannabis producers and tax revenues are squarely pitched against the health of Canadians. When Bill C-45 comes into force in mid-October, access to recreational marijuana will be legal, making Canada one of a handful of countries to legalize recreational use of the drug. Given the known and unknown health hazards of cannabis, any increase in use of recreational cannabis after legalization, whether by adults or youth, should be viewed as a failure of this legislation.

 – Dr. Diane Kelsall, Editor-in-Chief, CMAJ, October 2018

On Tuesday, Canada’s experiment with the legalization of cannabis for nonmedical purposes turned five. Did use go up? What about health care utilization? Have there been benefits from justice and social justice perspectives? Is it the failure that Dr. Kelsall feared?

Now is a good time to pause and review the impact of this change. In this Reading, we try to do just that. 

We start with a CMAJ commentary just published. Benedikt Fischer (of Simon Fraser University) and co-authors look at the evidence, including studies on use and ED presentations, as well as statistics on purchases. “A consideration of the evidence 5 years after implementation suggests that success in meeting policy objectives has been mixed, with social justice benefits appearing to be more tangibly substantive than health benefits.”

Dr. Leslie Buckley (of the University of Toronto) mulls this moment with some comments about the CMAJ paper, and the larger discussion. “[T]he legal changes were enacted and resulted in positive outcomes while the preventive changes which would require more financial investment and tight regulation received less attention.”

Finally, we look at three important papers on cannabis that have been featured in this series over the past five years, and another one that we haven’t looked at before.


“Outcomes associated with nonmedical cannabis legalization policy in Canada: taking stock at the 5-year mark”

Benedikt Fischer, Didier Jutras-Aswad, Wayne Hall

CMAJ, 10 October 2023

In October 2018, Canada was the first G-20 nation to implement the legalization of nonmedical cannabis use and supply for adults. Cannabis legalization in Canada had the primary objectives of improving cannabis-related public health and safety; reducing youth access to cannabis; and reducing cannabis-related crime and illegal markets, mainly by allowing adult cannabis use and related behaviours as a legal, regulated activity. We discuss whether, 5 years on, these objectives have been met, drawing on systematic reviews and recent primary studies for our observations.

So begins a paper by Fischer et al.

On use

“National survey data monitoring cannabis usage before and after cannabis legalization showed an increase in the prevalence of cannabis use (from 22% in 2017 to 27% in 2022), although rates of near-daily to daily use remained relatively stable (24%-25%). In contrast, significant increases in the prevalence of cannabis use (adjusted odds ratio [OR] 1.62…), daily cannabis use (adjusted OR 1.59…) and cannabis use–related problems (adjusted OR 1.53…) from 2001 to 2019 were shown in a study of the Ontario adult population. The prevalence of cannabis use among youth (30%-50%, depending on the survey) and perceived access to cannabis by minors have remained mostly stable at the high levels observed before legalization.” 

On ED visits

  • “A time-series analysis found a 20.0%… increase in emergency department presentations for cannabis-related disorders and poisonings among youth in Ontario and Alberta.”
  • “One population-based study in Ontario found a 12%-22% increase in cannabis-attributable adult emergency department visits since legalization to May 2021.” 
  • “Other Ontario studies have shown a 13-fold increase (0.26/100 000 people to 3.43/100 000 people) in monthly rates of emergency department presentations for cannabis hyperemesis syndrome, an increase in rates of emergency department visits for cannabis-induced psychosis (incidence rate ratio 1.30…) and a near doubling (11.0/100 000 people to 20.0/100 000 people) in acute episodes of pregnancy care in which cannabis was present…” 
  • “A recent repeated cross-sectional study reported an almost threefold increase in rates of emergency department visits related to cannabis poisoning among children (aged 0–9 yr) in 4 provinces in the year immediately after legalization, with further increases thereafter in those provinces allowing the sale of edible products.”

On legal purchases

“[T]wo-thirds of cannabis users purchase from legal sources, with levels varying between 50% and 80%, depending on the cannabis product type.”

On social justice

“[L]egalization significantly reduced enforced cannabis offences and arrests for adults (-74% females and -83% males…) and for youth, although to a lesser degree (-62% females and -53% males…), from 2015 to 2021. Before legalization, many criminal cannabis arrests were the result of highly arbitrary or discriminatory (e.g., racialized) enforcement practices, with many focusing on circumstances of personal cannabis consumption. The reduction in cannabis-related enforcement translates into substantive prevention of criminal penalties and criminal records – and the personal stigma and other adversities (e.g., restrictions on work, travel, social opportunities) arising from them for tens of thousands of Canadians – that occurred when use of recreational cannabis was legally prohibited in Canada.”

A few thoughts:

1. This commentary is an excellent review of the available evidence.

2. To summarize: a mixed picture. Use is up – but not among youth. There is greater health care utilization (at least ED visits). And cannabis-related crime is down.

3. Were some of these changes independent of legalization? The authors argue yes. “Some of the changing indicator rates or trends were evident before legalization, and the possibility that study findings represent an extension of these trends has not been assessed by all investigations.” 

4. How to understand this moment? Dr. Leslie Buckley makes some comments for the Reading of the Week below.

The full CMAJ commentary can be found here:

“Cannabis Policy: It’s Complicated”

Leslie Buckley

I read this CMAJ commentary with great interest. It is certainly true that even with the best of intentions and preliminary forecasting we do not always know what direction policy changes will take us. Measuring and summarizing outcomes are of the utmost importance. There were no surprises in the key points here, but there is much to consider in terms of why some policy goals were met while others were not. 

There is clear and substantial improvement noted with respect to social justice goals. It is a major win to see reductions in offenses and arrests which can have a profoundly negative impact on a person’s life. Data has shown that many arrests prior to legalization were highly arbitrary and biased towards marginalized groups. This is important progress and deserves an A+. In addition, with two-thirds of cannabis products now purchased legally, we have also seen progress here. 

But what about health outcomes? In this area, there is disappointment. With evidence of increasing use and increasing ED visits, we should be alarmed. The threefold increase in pediatric poisonings is unacceptable. Not noted in this paper is the recent evidence from CAMH scientists Hayley Hamilton and Yeshambel Nigatuu. Their Monitor Study e-Report 2022 documents a significant increase in the number of cannabis users reporting moderate to high risk of cannabis use problems (from 55 to 64%).

Why do we see these increases? There are many reasons why prevalence of use might increase including decreased deterrence, increased accessibility, and improved perceived safety of cannabis. We know that, in youth, perceived harm is a major factor in deciding whether to use cannabis. You can see how there could be cognitive misattribution such as: “they wouldn’t legalize cannabis if it was harmful?” In fact, there are other harmful substances that are legal and cannabis not being harmful was never part of the rationale behind legalization. Another factor related to increasing use may relate to a failure in the education and prevention goals of this policy change. With significant misinformation about cannabis present in media and considerable commercialization in recent years, there is an even greater need for prevention. It has been disappointing to see failed opportunities in terms of better regulation and prevention.

There are other factors at play as well. The report duly notes that COVID may have impacted use patterns and this could be different for youth and adults. For instance, adults may have increased use during COVID because of stress, while youth may have had less exposure and use because of decreased social contact. Further data collection in the coming years will more clearly illuminate prevalence trends. 

Why did only some recommendations get executed? One of the challenges of creating policy is that there are often multiple recommendations that are put forward related to the policy change, however, implementing all of these changes is extremely difficult. The recommendations may require cooperation amongst multiple levels of government and significant financial investment. In the case of cannabis, it seems that the legal changes were enacted and resulted in positive outcomes while the preventive changes which would require more financial investment and tight regulation received less attention. Many groups may sign on to a certain policy thinking all the recommendations will go forward and be disappointed in seeing a negative result because of the failure to carry through with the initial plan. This may be the case with cannabis in that we may be seeing a mixed outcome as a result of mixed implementation of recommendations. 

It is fortunate that we have examples of different strategies across provinces. Quebec, for instance, implemented a minimum age of 21, while Ontario chose 19, and we can follow use trends to see if this difference impacts youth use in each province. We can learn much about the impact of different policies through such natural experiments.

As a final note, I am worried about what we don’t yet know about cannabis. We don’t know enough about long-term physical harms and I believe we don’t know enough about the impact of higher THC products and more frequent use on mental health. A good take-home message from this commentary is to recognize the increasing use and harms of cannabis and therefore the importance of asking about cannabis in your practice. Providing good information about known harms and informing patients that cannabis does not improve anxiety and depression may go a long way in offsetting the opposite messages people may be hearing elsewhere. 

Dr. Leslie Buckley

Major Papers

Here are four must-read papers:

“Risks and Benefits of Cannabis and Cannabinoids in Psychiatry”

Kevin P. Hill, Mark S. Gold, Charles B. Nemeroff, et al.

The American Journal of Psychiatry, February 2022

What does the literature say? This paper is incredible – Dr. Kevin P. Hill (of Harvard University) and his co-authors review almost 850 papers and comment on everything from the potential therapeutic effects of cannabis to acute, chronic, and indirect effects of use on health. The final paper is lucid, clear, and highly relevant.

Hill et al. offer clear clinical guidance:

“The level of evidence supporting cannabinoids for treating anxiety is low, despite the anecdotal reports describing its efficacy. When patients report that cannabinoids provide subjective relief of anxiety, psychiatric clinicians have an opportunity to provide education about the current state of the evidence. Since the number needed to harm is likely to be much lower for THC-containing compounds than those with pure CBD, clinicians whose anxious patients are reporting benefits from THC may consider recommending a monitored trial of CBD instead.

“In general, however, prescribing clinicians should avoid initiating or recommending cannabinoid pharmacotherapy for most psychiatric patients. There are no clinical trials that support the use of cannabinoids as pharmacotherapy for mood disorders, and there is limited evidence supporting their use in PTSD. Converging lines of evidence suggest that THC-containing compounds are likely to cause harm in patients with existing psychosis or at high risk for psychosis.”

“Cannabinoids in psychiatry: they are here to stay”

Julia Jiyeon Woo, Emma van Reekum, Sagnik Bhattacharyya, Zainab Samaan  

The British Journal of Psychiatry, June 2022

Dr. Julia Jiyeon Woo (of McMaster University) and her co-authors consider cannabis from the perspectives of clinicians and patients. In a British Journal of Psychiatry paper, they note the growing enthusiasm of patients and the concern of providers, adding: “This growing discrepancy between clinicians’ and patients’ perspectives on cannabinoids can be extremely damaging to the therapeutic alliance.” 

They offer some advice to us clinicians:

  • “Substance use history is a vital aspect of any psychiatric assessment, but one that too often turns into a checklist of closed questions.”
  • “Questions such as these could go a long way in creating an environment where patients feel understood; one in which constructive discussions and education can take place. Better understanding of our patients’ patterns and perception of cannabinoid use would allow us to shape our psychoeducation accordingly.”
  • “Perhaps more transparency and humility are also needed from clinicians. We can let our patients know with relative confidence that (a) there is limited evidence that cannabinoids are effective in treating mental illnesses and (b) there is convincing evidence to suggest harms of regular, long-term use of cannabinoids, particularly THC. Beyond that, our current knowledge of cannabinoids is quite limited.”

More and more we need to speak to our patients about cannabis. This paper is relevant and helpful.

Canadian Network for Mood and Anxiety Treatments (CANMAT) Task Force Report: A Systematic Review and Recommendations of Cannabis use in Bipolar Disorder and Major Depressive Disorder” 

Smadar V. Tourjman, Gabriella Buck, Didier Jutras-Aswad, et al.

The Canadian Journal of Psychiatry, May 2023

Many people with mood disorders use cannabis. Dr. Smadar V. Tourjman (of the Université de Montréal) and her co-authors look at the impact of use with a systematic review, drawing on data from 56 studies, focused on bipolar and major depressive disorders, for a CANMAT task force report.

They conclude: “Cannabis use was associated with worsening course and symptoms of both mood disorders, with more consistent associations in bipolar disorder than major depressive disorder: increased severity of depressive, manic and psychotic symptoms in bipolar disorder and depressive symptoms in major depressive disorder. Cannabis use was associated with increased suicidality and decreased functioning in both bipolar disorder and major depressive disorder.”

Their recommendation? “Considering the consistent signal for the deleterious effects of cannabis in BD and based on the clinical experience of experts, CANMAT provides a strong recommendation against CU use in this disorder. On the other hand, the inconsistency of the signal regarding the effects of cannabis in MDD contributes to a qualified level of recommendation against its use in this disorder…”

“An examination of cannabis related information typically asked by consumers at retail cannabis locations: A Canadian survey of budtenders and managers”

Jameason D. Cameron, Rahim Dhalla, Taylor Lougheed, et al.

Canadian Pharmacists Journal, May/June 2023

What are people asking at licensed recreational cannabis stores? Jameason D. Cameron (of the University of Ottawa) et al. attempt to answer that question by surveying the people who are selling cannabis.

In all, 91 budtenders and 120 managers responded to their survey which has 22 questions. For the record, the vast majority – 87.7% of respondents – indicated that they “receive questions related to cannabis use for medical purposes and/or perceived medical benefit.” And the vast majority indicated that they “have been told by a customer that their physician sent them to obtain a cannabis-containing product for medical purposes.” Some of the most common questions included help with sleep. 

They conclude:

“An alarming proportion of budtenders and managers in Canada report that they are fielding medical cannabis questions. This situation has the potential to put individuals at risk for drug-drug interactions and drug-disease interactions and to increase unnecessary hospitalizations due to adverse effects.”

Many thanks to Dr. Buckley for her contribution to this week’s Reading. Dr. Tony George (of the University of Toronto) made suggestions for the papers to include – which is greatly appreciated.

Reading of the Week. Every week I pick articles and papers from the world of Psychiatry.