Yes, thank you to the Chair and the members of the committee for allowing me to speak. In fact, my colleagues Doctors Le Foll and Mizrahi have covered a lot of background that I think is very relevant to understanding addiction risk with cannabis and also its mental health affects.
I am an addiction psychiatrist by training who focuses on treating and understanding substance use disorders in people with serious mental illness like schizophrenia and bipolar disorder. I'm a professor in the Department of Psychiatry here at the University of Toronto, as well as the Chief of the Schizophrenia Division, and Medical Director of the Complex Mental Illness Program here at CAMH, which treats the majority of people with serious and persistent mental illness.
I've been involved in research in these populations for about 20 years now, and what I want to focus on is the necessity for treatment of cannabis use disorders, particularly in those who have high vulnerability to initiating and maintaining these disorders, such as people with mental illness like schizophrenia. We know that there are much higher rates for use of cannabis and other drugs. Most of my career has been spent on tobacco use in psychiatric populations, but the reasons for this increase and their inability to quit are less clear. I want to talk to you about some studies we've done in cannabis patients with schizophrenia that really point to the need for getting these people into treatment.
Over the last couple years, we've done a series of studies trying to understand what cannabis use does to the symptoms of schizophrenia and cognitive function—cognitive function being processes like memory, attention, concentration, judgment, and planning. Basically, what our studies have shown is that if you look at cognitive functions in these patients as a function of whether they are currently using cannabis and are dependent, whether they have a history of abusing but have recently stopped, or have never used it, you actually find no significant differences in cognitive functioning, particularly as assessed by certain forms of memory, like working memory.
However, what's of concern is that we find that the more people use cannabis over time—what we call cumulative use; that is total exposure over time—the more of that cumulative exposure over time, the more impairment of frontal lobe cognitive functioning such as working memory, judgment, attention they have. We think of the frontal lobes as sort of the master or CEO of the brain.
In fact, cannabis use over time impairs it in our patients, and we know that they have pre-existing deficits, so to know that cannabis use over time, heavy and persistent cannabis use over time, will further impair their cognitive function, which we know is associated with their success in functioning in the community. So that's of great concern to us.
At the same time, some of our studies have suggested that in those patients who have quit using cannabis for at least six months, those cognitive functions actually are restored and those deficits produced by heavy and persistent cannabis use actually start to normalize and reverse. So that's very important from a treatment implication because it suggests that we can develop effective pharmacological, that is medication, and behavioural treatments for treating cannabis-use disorder. We can significantly help outcomes in these high-risk patients with psychiatric disorders like schizophrenia.
We're in the midst of doing a study to look at what cannabis truly does by taking patients who are currently using cannabis and are dependent on it and withdrawing them from cannabis for up to 30 days. This is the first time that anyone, to our knowledge, has done this, and that data should be complete by this time next year. We're hoping to know truly what cannabis does to cognitive function, clinical symptoms, and outcomes in people with schizophrenia who are cannabis dependent, and non-psychiatric controls as a comparison route.
The other thing I want to point out, as Dr. Mizrahi says, is that many of these young people that go on to develop psychotic disorders like schizophrenia may be genetically predisposed to cannabis-induced worsening or initiation of their psychosis.
For example, there is a gene called catechol-O-methyltransferase, COMT, for short, that at least one form, which is present in about 36% of the general population, makes you five to ten times more vulnerable to having psychosis when you use cannabis. In fact, from a prevention point of view, if we knew something about the genetic background of these individuals—which is a controversial thing because having this kind of genetic information from a population base needs a lot of thinking in terms of how we would do it. However, suffice to say that if we had this information available to those who are at risk, we could design and tailor interventions, like behavioural interventions, to increasing knowledge about how cannabis could potentially worsen this subset of individuals.
The other thing I'll say, clinically, as an administrator here at CAMH, is that one of the in-patient units we have is called the early psychosis unit, and most of the young people who develop early psychosis, or have their first experience with psychosis, end up being admitted to this unit. We know that at least 50% of those admissions are associated with cannabis use. That's concerning, and again speaks to the importance of prevention.
I'll leave you with the following issue. In terms of decriminalization as relevant to this population, the concern with the current regulations is that to penalize this group who are vulnerable to cannabis addiction through legal penalties is potentially deleterious and could very well prevent these people from seeking treatment, which I hope we have underscored is the important thing.
The other point is that we know from the studies that have been done on decriminalization versus continued criminalization of cannabis that there is little or no evidence that decriminalization increases rates or uptake of cannabis. The concern has been that this would be seen in young people, whom Doctors Mizrahi and Le Foll have said that we worry cannabis can affect brain development in a negative way. However, we have seen little evidence of an increase in cannabis use with decriminalization.
Moreover, we tend to see that it's those people, who would have gone on to use cannabis anyway, who might start using at an earlier age. But, in fact, you see no increase in the rates of use. Again, it conjures to me the importance of a treatment approach, a public health integrated approach, and also educating young people about the potential harm.
There is the Monitoring the Future study, in the United States, that for many years has very clearly shown that if you can increase the perception of harm among youth, the rates of cannabis use goes down, and when harm is considered to be low, that's when cannabis use goes up. It speaks to the importance of a targeted public health and treatment-based approach. It is a call for us, as Canadians and as Canadian society, to embrace the fact that there is harm associated with cannabis, but it can be mitigated with proper education and treatment strategies.
Let me stop there. Thank you for the opportunity to speak to you.