Good afternoon, honourable members of Parliament. I appreciate the opportunity to address this committee on this important topic.
At McMaster University and St. Joseph's Healthcare Hamilton, I hold the Peter Boris chair in addictions research, and I direct the Peter Boris Centre for Addictions Research and the Michael G. DeGroote Centre for Medicinal Cannabis Research.
I've dedicated my career to understanding addiction and, more recently, to advancing the science of medical cannabis.
With regard to the DeGroote Centre, I want to note that the central operations of the centre are supported by philanthropy, not by industry. Our mission is to develop an evidence-based understanding of medical cannabis both in terms of positive therapeutic effects and potential negative side effects.
Our highest priority is the objective study of cannabis, just like any other drug in medicine.
We exist not because we believe that cannabis is or is not an effective medicine, but because we're sure there's a need for more research on the topic.
I've personally published research documenting both the risks and harms from cannabis use and also its potential therapeutic applications. I'm neither pro-cannabis nor anti-cannabis. I am pro-evidence, and I'm pro evidence-based medicine and pro evidence-based policy.
As a preface to my comments, I am mindful of the sacrifices that are made by veterans. As part of my clinical training, I was at the U.S. Providence veterans administration hospital working directly with veterans. I'm aware of how common the conditions they often use cannabis for are and that those conditions are often a result of their service.
Moreover, over 8,000 Canadian veterans are currently authorized for medical cannabis, and I know that the decisions around policies will have significant effects on their lives.
My comments today are from the perspective of trying to use the best available evidence to advance the health and well-being of Canadian veterans.
I'm aware of the six priority topics, and I will comment on three areas where I have the greatest expertise. I'm happy to discuss other topics also.
The first priority topic is the scientific basis for the policy for reimbursement of up to three grams of cannabis in general and up to 10 grams with additional approval, and that's daily.
Is this amount the right amount? Is it too high? Is it too low? Unfortunately, precise dosing is not available from the current research. This is one of the ways that medical cannabis is different from traditional medicine.
The reality is that this is not a drug with a DIN, a drug identification number, like other drugs have. It's a plant, not a pill. It's a plant that has dozens of different compounds that interact with the body's internal endogenous cannabinoid system. The interaction of these compounds is believed to be part of the reason for its positive effects.
In addition, there are many different routes of administration, not just as a capsule, like most medications, but via inhalation and other routes. This could affect the effects, also.
To put this in context, for non-medical users three grams daily would be considered a very high level of use, and 10 grams daily would be considered an extremely high level of use. In research, we standardize a gram as being equivalent to about four cannabis cigarettes, or joints. These numbers equate to 12 and 40 joints per day, which would be a large amount of cannabis.
The reality is that pharmacology doesn't make any distinction between medical use and non-medical use. The more cannabis a person consumes, the higher the risk of adverse consequences.
A person who's consuming, for example, 10 grams of cannabis each day would be more likely to experience physiological dependence and other adverse side effects, such as cognitive difficulties, motor impairment, or risk for cannabis-use disorder, the technical term for addiction to cannabis. It's also the case that withdrawal symptoms would be more likely in high-dose patients.
In this context, I am not proposing or recommending any immediate changes or restrictions. The reality is that abruptly reducing access or making other policy changes that would dramatically increase the cost of cannabis to active medical patients could have adverse consequences.
I do believe, however, it's important that veterans who are using medical cannabis do so closely in contact with their treatment providers to monitor their progress and minimize potential harms.
With regard to the second topic, evidence for medical cannabis for chronic pain and PTSD, unfortunately, the utilization of cannabis in these contexts has outpaced the research on this topic.
For chronic pain, a recent review of numerous studies suggested that there is a small therapeutic effect on pain, but there were high rates of side effects, and the side effects were more common than the positive response.
In another recent review, when restricted to neuropathic pain, there was again evidence of a positive effect, this time larger than for general pain, but side effect rates were very high and patients who were taking medical cannabis for pain were more likely to drop out of trials.
On balance, both of these reviews concluded that although there is positive evidence for pain, the evidence for side effects may suggest that the benefits are outweighed by the harms. It's also worth noting that in these reviews, no trials to date have been conducted on Canadian veterans, so all of this is by analogy, rather than based on evidence we have in this population.
With regard to PTSD and other anxiety disorders, there are intriguing preclinical findings using animal models. There are anecdotal and case study reports that are promising, but there are no gold standard randomized controlled trials that show evidence of efficacy, either in civilian or veteran populations. At this point, there is insufficient evidence that cannabis is effective in treating PTSD or other anxiety disorders.
These are my personal conclusions, but they are very similar to the conclusions reached in a recent report by the U.S. Department of Veterans Affairs with regard to the benefits and harms of cannabis for pain and PTSD for United States veterans.
There are other circumstances in which cannabis has been shown to be helpful: reducing chemotherapy-induced nausea and vomiting, reducing spasticity in multiple sclerosis and reducing seizure frequency in children with rare pediatric seizure disorders. These are all areas where the evidence is more robust. That is not the case for pain and PTSD.
On the topic of how legalization will affect medical cannabis for veterans, there's a risk that individuals who have current authorizations may augment the amount available with additional non-medical cannabis that is legal. It's also possible that veterans who are considering getting an authorization will simply explore it and self-medicate without engaging with a health care provider. This could result in harms by way of individuals inadvertently accessing products that would be considered high risk. High THC products that have low rates of CBD can have a cannabidiol, a constituent that's believed to be responsible for the therapeutic actions to an extent.
The other reality is that, because there are known risks, any medical use, in my opinion, should take place in collaboration with a health care provider.
Finally, given that the market for recreational cannabis will necessarily be much larger than the medical cannabis market, it's possible that the products used primarily for medical purposes will become increasingly unavailable. Those are products like oral capsules, oral oils or high CBD products. In my opinion, it's important that Health Canada's dual system for medical and recreational cannabis be fully implemented and supported.
In this context, I would argue that there's a high need for large scale, coordinated research on medical cannabis for veterans in Canada. There are literally thousands of veterans who are effectively accessing what could most charitably be described as an experimental medicine, rather than an evidence-based medicine. Because there is evidence from U.S. veteran populations of the association of cannabis with suicidality and self-harm, the risk for true harm is present.
In terms of the research that we need, we need observational research to understand the effects that are happening among individuals who are currently using cannabis. We also need randomized control trials to actually test, using gold standards, cannabis for pain and PTSD. We also need more knowledge translation and guideline development efforts to make veterans aware of the realities of risks, and to give clinicians clear recommendations about best practices.
As a final point, it's important to remember that Canada still has a major opioid epidemic that has not abated. Increases in access to opioids, and a combination of overestimated efficacy and underestimated risk has contributed to the current epidemic. Those are lessons to be learned in the context of medical cannabis and for cannabis post-legalization in general. In my opinion, the bottom line is that excessive optimism can lead to real harm here.
Thank you for the opportunity to serve as a witness for this committee.