Thank you very much. Good afternoon, honourable members of Parliament. I appreciate the opportunity to address the House of Commons Standing Committee on Veterans Affairs.
As noted, I'm an associate professor in the department of anaesthesia here at McMaster as well as the associate director in our cannabis research institute.
The cannabis research institute here is funded by philanthropic donation. We receive no industry funding, and our mission is to develop an evidenced-based understanding of cannabis, both in terms of its potential therapeutic benefits and also its associated harms.
Our centre's activities broadly include the synthesis and dissemination of current best evidence, the conduct and support of innovative research in areas where evidence is lacking, and the creation of a research network including both faculty members at McMaster and external partners including Dr. David Pedlar, the scientific director of the Canadian Institute for Military and Veteran Health Research.
My research in particular focuses on evidenced-based medicine, chronic pain, disability management, opioids and cannabis.
We note that military service is associated with health risks. Recent surveys have found 41% of military personnel report the experience of chronic pain and 23% report intermittent pain. Military personnel develop higher rates of psychiatric disorders such as PTSD and anxiety than members of the general public, and they are at greater risk for both suicide attempts and completion.
Regarding the potential role of medicinal cannabis to assist our veterans, we have at present moderate quality evidence that suggests cannabis may reduce chronic pain, but effects are typically modest. Our group here at McMaster is currently revising and updating this evidence synthesis. We anticipate our work will be completed in the first half of 2019.
Regarding the current evidence to support a therapeutic role and management of symptoms associated with anxiety or PTSD, we have anecdotes but we have very little evidence to make conclusions either supporting a benefit or refuting a role.
We have some observational evidence that has shown that, in areas where cannabis becomes available for medicinal use, suicide rates in general seem to track down. We also have observational evidence that veterans who present with cannabis use disorder are at higher risk for suicide attempts. This is another area where more research is needed before we can make firm conclusions.
There are a number of side effects associated with cannabis. These include dizziness, fatigue, euphoria, confusion, disorientation. Cannabis use disorder or addiction occurs in about 7% of regular users over their lifetime, and the adverse events associated with cannabis are predominantly tied to one cannabinoid, THC. The cannabis plant contains more than 100 active cannabinoids, the most studied of which being THC and CBD. CBD may have some therapeutic properties, but it is neither psychoactive nor addictive.
This suggests that cannabis products that contain predominantly CBD may be associated with much fewer adverse events than the plant as a whole. Despite the limited evidence for benefits and the known and suspected harms, the general perception about cannabis seems to be increasingly enthusiastic.
A 2017 survey of more than 16,000 Americans in the general public found that 81% believed cannabis had health benefits; 9% believed it had no risks; 22% believed it was not addictive. These perceptions are not in line with current evidence.
We also know that authorization for medicinal use is increasing in Canada. According to Health Canada's registry of patients, there were about 8,000 who were authorized to use medicinal cannabis in 2014, and at present this figure is closer to a quarter of a million. The rapidly expanding therapeutic use of cannabis suggests a triumph of marketing over evidence. I would suggest there may be some relevant lessons to be learned from Canada's experience with opioids for chronic pain.
At present, over 7,000 veterans in Canada have been authorized to receive medicinal cannabis, and the matter of dosing has been contentious. The precise dosing is not available from current evidence, and a dose of cannabis does not consider the potency, particularly the percentage of THC that may be available in a product. In addition to that, the product of cannabis can be consumed either through inhalation or through ingestion and the way in which you take it in affects both the time of onset and the duration of effects.
VAC currently reimburses up to three grams per day in general for medicinal cannabis and up to 10 grams with approval for exceptional cases. These are not excessively conservative policies relative to other countries. For example, Israel reimburses only one and a half grams per day, the Netherlands 0.68 grams per day. If you look at the data from Health Canada regarding how much cannabis those who are authorized to use it for medicinal purposes are currently accessing, on average it's about 0.75 grams per day. The likelihood of an individual consuming the very high end of what's allowed, 10 grams per day, suggests they are at higher risk for developing dependence and possibly cannabis use disorder. The result of this means that withdrawal symptoms would result if their dose were tapered rapidly or if the product were made unavailable to them, and as such there is a need for both caution and compassion considering veterans who are currently using medicinal cannabis, in particular at higher amounts.
What is needed to promote evidence-based authorization of medicinal cannabis? We need randomized controlled trials to establish effectiveness of cannabis for promising indications. Observational data, which is what we have most of, cannot establish causation, and such trials should enrol adequate numbers of patients to make firm conclusions, follow individuals for a long period of time, six months to a year, and consider capturing both benefits and harms of cannabis use. We require more real-world observational data at the same time. Veterans and other medicinal cannabis users can be enrolled in research cohorts and followed forward in time to look at patterns in change of use, the effect on their symptoms and the development of both long-term and rare events.
We also need guidelines to help veterans, other patients and clinicians make evidence-based decisions around medicinal cannabis. The most applicable area for this would be chronic pain. That's where we currently have the bulk of evidence for the application of medicinal cannabis.
At the same time, evidence alone is not sufficient to make clinical decisions. Because of the likely modest benefits, and the known and suspected adverse events, the decision to pursue a trial of therapeutic cannabis is not straightforward. We require values and preference research so we understand what patients are willing to trade off, given the evidence for potentially modest benefits and the development decision aids would help facilitate shared care decision-making.
On a positive note, with the dedication of appropriate resources, given the current legalization of cannabis and the interest in research, Canada has the opportunity to become an international leader in medicinal cannabis research for both veterans and in general.
In closing, I thank you for the opportunity to serve as a witness for this committee.