A position statement developed by the Canadian Psychiatric Association's (CPA) Research Committee and approved by the CPA's Board of Directors on May 13, 2020.# 
The Canadian Psychiatric Association (CPA; www.cpaapc.org) is the professional association for over 4,700 psychiatrists and 900 psychiatry residents in Canada. In addressing its mission, the CPA uses evidence-based methods to not only educate and inform the public and its own membership but also to develop mental health programs, services and policies.
In response to the federal government legalizing and regulating access to cannabis in 2017, the CPA published a position statement with respect to cannabis use and adverse health consequences in youth and young adults 1 based on the accumulating evidence of negative consequences of early sustained use (e.g., National Academies of Sciences and Medicine, 2017). 2 However, psychiatrists and other mental health professionals are also being asked about the potential therapeutic uses of cannabis and cannabinoid products for mental illnesses; information is widely distributed on cannabis use being associated with mental wellness and suggesting cannabis use as a treatment for a variety of mental health concerns. As the CPA is evidence based, it is prudent to examine the existing research in this area to inform our membership needs and thus the public.
In Canada, before a new medication can be approved (or, an existing medication can be prescribed to treat a previously unrecognized condition), it must pass through Health Canada's regulatory approval process. As part of this process, clinical trial data must show a positive therapeutic effect on symptoms and that this effect is not associated with significant risks (e.g., potential side effects). For therapeutic indications and clinical decision making, Level 1 evidence is usually required. Level 1 evidence includes systematic reviews of randomized control trials (RCTs) or high-quality individual RCTs (see Centre for Evidence-based Medicine for details, http:// www.cebm.net.)
The CPA has systematically reviewed the existing literature on RCTs examining potential beneficial uses of cannabis and cannabinoid products to treat mental illness. This review incorporated studies in adults only (greater than 18 years old). Of the 1,982 papers identified, 29 RCTs were available to review (see Figure 1 for systematic review flow diagram). Methodological quality for each study was assessed using Cochrane Collaboration guidelines. 3 The 29 publications were in the following clinical areas: anxiety disorders (three RCTs),  posttraumatic stress disorder (one RCT), 7 psychotic disorders (six RCTs),  anorexia nervosa (two RCTs), 14,15 cannabis dependence management (nine RCTs),   The Canadian Psychiatric Association-Position Statement nicotine/opioid dependence (five RCTs),  attentiondeficit hyperactivity disorder (one RCT) 30 and Tourette's disorder (two RCTs). 31,32 The clinical trials identified followed accepted designs (parallel or crossover design methodology); however, sample sizes were relatively small in most of the RCTs, which weakens the conclusions, and they evaluated a variety of naturally derived and synthetic tetrahydrocannabinol (THC; e.g., nabilone, dronabinol, nabiximols) and cannabidiol products at varying doses across studies, making comparisons difficult. Results were often not specific to the primary psychiatric symptoms that the trial was designed to address. Of note, no studies used combustible dried cannabis or cannabis edibles. Results of some studies showed atypical doseresponse effects. Also, there were no RCTs investigating the potential benefits of cannabinoid products in major depressive disorder (i.e., clinical level depression) or bipolar disorders. While different inclusion and exclusion criteria were used for manuscript selection, the results discussed here are comparable to another recent systematic review and meta-analysis on this topic. 33 With respect to the use of cannabis and cannabinoid products in mental illness, based on the current evidence, the CPA: