Good afternoon, bonjour, honourable members of the committee and my esteemed colleagues. I would like to express my sincerest gratitude for the honour to be here today.
My name is Dr. Yanbo Zhang. I am a clinician scientist from the department of psychiatry in the college of medicine at the University of Saskatchewan. As a psychiatrist, I treat patients with mental health conditions like depression, anxiety and PTSD. As a researcher, I use animal models to study the therapeutic effects and underlying mechanisms of cannabis as well as other normal treatments for psychiatric and neurological disorders such as depression, PTSD, multiple sclerosis and also traumatic brain injury.
I want to declare my funding sources and potential conflicts of interest. I received research grants from the University of Saskatchewan and also the Saskatchewan Health Research Foundation. I have an ongoing supply agreement from a cannabis company for my animal research, but the company does not influence my experiment design or the outcome of the research. I do not have any financial support or grants received from any industry.
I'm also the secretary-treasurer and the board executive for the Canadian Psychiatric Association. It’s a national professional organization for Canada's psychiatrists and trainees, but here all my opinions are my own, and I do not really represent any of our association’s opinions.
Military veterans have at least a twofold risk of developing PTSD when compared to the general Canadian population. Individuals with PTSD relive trauma through flashbacks and nightmares, and they suffer from extreme fear, irritability, hyper-arousal and negative emotions. Untreated PTSD causes severe and chronic impairment in their cognition, physical health and social functioning.
Psychotherapies are considered the primary interventions for PTSD. Trauma-focused cognitive behavioural therapy, called CBT, is by far the best supported method. CBT aims to change patients’ dysfunctional post-traumatic memories and beliefs and then to reduce or to decrease their response and avoidance towards the traumatic memory. However, due to the stigma, the service access, the cost and the time consumption, few patients engage in psychotherapy. Most patients with PTSD also receive medications like antidepressants, antipsychotics and mood stabilizers, but seldom stay on the medications due to side effects or lack of observed benefit.
Overall, the treatment of PTSD and the outcome are not promising. Studies also suggest that combat-related PTSD is more refractory to current treatments, which is probably due to high a comorbidity of brain injuries, chronic pain, addiction and also some other comorbidities. Medical cannabis has been allowed for PTSD treatment in a few countries, such as, Israel, Holland and Canada.
Although increasing preclinical studies suggest a critical role of the endocannabinoid system in PTSD and the potential of cannabis in treating PTSD, the clinical evidence remains inconsistent. Most trials have limitations, such as, a small sample size or the use of some healthy participants to elicit the anxiety symptoms rather than a real-world PTSD patient. They also use a synthesized cannabis product rather than the whole plant. In addition, the therapeutic dose range and the ratio of different compounds and their effects is unknown.
The systematic reviews, which are the strongest evidence that we normally use to guide treatment, cannot come with the conclusion of any definite therapeutic effects or benefits in terms of cannabis treatment for PTSD.
With little information, the physicians, pharmacists and patients cannot make an informed decision because there's no high quality of randomized and controlled trials on the whole planet of cannabis, which is the major product that has been distributed. It's really difficult for us to make a decision to see whether it should be used or not and what the benefit would be.
Also, there's consistent evidence showing that the heavy and regular use of cannabis with a high THC content is associated with increased risks of cognitive impairment, psychosis and cannabis use disorder, especially in adolescents and young adults, and also in individuals with pre-existing mental health conditions. Given the high comorbidity of depression, traumatic brain injury and substance abuse in veterans with PTSD, the potential benefit of cannabis may be shadowed by the increased risks of cognitive impairment and addiction.
As psychiatrists we are trained to practise evidence-based medicine, which requires us to examine the scientific evidence and to balance the risks and benefits before providing treatment. Thus, many psychiatrists, including myself, are really hesitant to authorize cannabis for treating any psychiatric disorders because we do not know the long-term outcome and we do not know whether the benefit will trump the risk.
On the other hand, effectively treating PTSD is quite a challenging thing. We have to explore new interventions that can benefit our patients. That's why it is critical to understand the therapeutic and adverse effects of cannabis products with different doses and with different ratios of THC and CBD. Research to compare the efficacy of cannabis use and also the currently available treatment, like antidepressants and psychotherapies, are highly needed, so we can find a benefits versus risks profile. Also, we need to determine the long-term effects of cannabis use on the patient's mental, physical and social functions, which is largely lacking at this stage.
The third part is we know that there's a high comorbidity of chronic pain and brain injury and substance use in patients with PTSD. They have a really complicated bidirectional relationship. Adding more studies on the interactions will help us to understand the prevention and the treatment options for the future.
Before obtaining further evidence, the low-risk cannabis use recommendations made by medical professionals should be applied, such as using a high CBD content oil versus using or smoking products with a high content of THC. I believe that the safe integration of medical cannabis can potentially improve the quality of care for the patient, but the robust, large-scale and blind and unbiased studies are needed to achieve this.
Thank you.