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Cannabis use may increase the risk of self-harm, but whether legalization of cannabis is associated with changes in self-harm is unknown. We examined changes in cannabis-involvement in emergency department (ED) visits for self-harm after the liberalization of medical and legalization of non-medical cannabis in Canada. This repeated cross-sectional study used health administrative data to identify all ED visits for self-harm in individuals aged ten and older between January 2010 and December 2021. We identified self-harm ED visits with a co-diagnosis of cannabis (main exposure) or alcohol (control condition) and examined changes in rates of visits over four distinct policy periods (pre-legalization, medical liberalization, non-medical legalization with restrictions, and non-medical commercialization/COVID-19) using Poisson models. The study included 158,912 individuals with one or more self-harm ED visits, of which 7810 (4.9 %) individuals had a co-diagnosis of cannabis use and 24,761 (15.6 %) had a co-diagnosis of alcohol use. Between 2010 and 2021, the annual rate of ED visits for self-harm injuries involving cannabis per 100,000 individuals increased by 90.1 % (3.6 in 2010 to 6.9 in 2021 per 100,000 individuals), while the annual rate of self-harm injuries involving alcohol decreased by 17.3 % (168.1 in 2010 to 153.1 in 2021 per 100,000 individuals). The entire increase in visits relative to pre-legalization occurred after medical liberalization (seasonally adjusted Risk Ratio [a s RR] 1.71 95 % CI 1.09–1.15) with no further increases during the legalization with restrictions (a s RR 1.77 95%CI 1.62–1.93) or commercialization/COVID-19 periods (a s RR 1.63 95%CI 1.50–176). Cannabis-involvement in self-harm ED visits almost doubled over 12 years and may have accelerated after medical cannabis liberalization. While the results cannot determine whether cannabis is increasingly causing self-harm ED visits or whether cannabis is increasingly being used by individuals at high risk of self-harm, greater detection for cannabis use in this population and intervention may be indicated. • Of the 158,912 self-harm ED visits in Ontario, Canada between 2010 and 2021, 4.9 % involved cannabis. • The annual rate of self-harm ED visits with cannabis involvement increased by 90.1 %. • Medical cannabis liberalization was associated with these increases. [ABSTRACT FROM AUTHOR]

Despite evidence showing that recreational cannabis use is associated with a higher risk of psychotic disorders, this risk has not been well characterized for patients using medical cannabis. Therefore, this study assessed the risk of emergency department (ED) visits and hospitalization for psychotic disorders (the study outcome) among adult patients authorized to use medical cannabis. We performed a retrospective cohort study on patients authorized to use medical cannabis in a group of Ontario cannabis clinics between 2014 and 2019. Using clinical and health administrative data, each patient was matched by propensity scores to up to 3 population-based controls. Conditional Cox proportional hazards regressions were used to assess the risk. Among 54,006 cannabis patients matched to 161,265 controls, 39 % were aged ≤50 years, and 54 % were female. Incidence rates for psychotic disorders were 3.00/1000 person-years (95%CI: 2.72–3.32) in the cannabis group and 1.88/1000 person-years (1.75–2.03) in the control group. A significant association was observed, with an adjusted hazard ratio of 1.38 (95%CI: 1.19–1.60) in the total sample and 1.63 (1.40–1.91) in patients without previous psychotic disorders. The results suggest that cannabis authorization should include a benefit-risk assessment of psychotic disorders to minimize the risk of events requiring emergency attention. [ABSTRACT FROM AUTHOR]

• Examined risk perceptions of driving under the influence of cannabis (DUIC) and alcohol (DUIA). • Compared perceptions of non-medical (ie. recreational) to medical or dual-purpose cannabis users. • Medical or dual-purpose users were more likely to agree that DUIC is safer than DUIA. • No difference found in perception that DUIC increases collision risk. • No difference found in perception that risk of police enforcement is higher for DUIA than DUIC. Reduced perception of potential harm resulting from cannabis use is associated with greater risk of driving under the influence of cannabis (DUIC). Understanding risk perceptions of DUIC among subgroups of users will positively inform targeting and content of anti-DUIC driver education and public awareness campaigns. The current study compared DUIC-related risk perceptions among individuals who use cannabis exclusively for non-medical purposes versus those who use cannabis for exclusively medical or for both medical and non-medical purposes (i.e., dual-purpose users). Data were drawn from a regionally stratified cross-sectional general population telephone survey of adults (18 + years) in Ontario, Canada conducted in 2017. Respondents who reported past-year use of cannabis and answered questions regarding DUIC risk perceptions were selected (weighted N = 343). Modified Poisson regression models with robust standard error estimation were conducted for three attitudes: disagree that DUIC increases motor vehicle collision risk, agree that DUIC is safer than driving under the influence of alcohol (DUIA), agree that chances of being caught by police for DUIA higher than DUIC. In addition to type of cannabis user (non-medical only versus medical or dual-purpose), covariates included demographic characteristics and past-year alcohol and cannabis use frequency. Adjusting for other covariates, regression analyses indicated that medical or dual-purpose cannabis users were 45 % more likely than non-medical users to agree that DUIC is safer than DUIA (Adjusted Prevalence Ratio = 1.45, 95 %CI = 1.10, 1.91, p = 0.007). No other differences in risk perception between medical or dual-purpose and non-medical cannabis users were found. Although no difference between medical or dual-purpose and non-medical cannabis users was found in perceptions of collision risk associated with DUIC or risk of police enforcement, the perception that DUIC is safer than DUIA was stronger among medical or dual-purpose than non-medical users. Recognizing that the shift in public perception of DUIA as a high-risk behaviour contributed to reductions in incidence of DUIA, results of the current study support education and awareness campaigns that target medical or dual-purpose users and emphasize that, like DUIA, DUIC is also a high-risk behaviour. [ABSTRACT FROM AUTHOR]

• What is already known on this topic ? Cannabis is increasingly used to treat many conditions including depression without conclusive evidence of its safety and effectiveness for most of the treated conditions. Recreational cannabis use is associated with increased risk of mental health disorders. • What this study adds ? This study assessed the data of 54,006 patients who received medical cannabis authorization and 161,265 matched controls and showed that medical cannabis authorization was associated with an increased risk of emergency department visits or hospitalization for depressive disorders. • How this study might affect research, practice or policy ? The finding highlights the need for a careful risk-benefit assessment when authorizing cannabis, particularly for patients who seek cannabis to treat a depressive condition. There is an increase in the medical use of cannabis. However, the safety of medical cannabis, particularly for mental health conditions, has not yet been clearly established. Thus, this study assessed the risk of emergency department (ED) visits and hospitalization for depressive disorders among medical cannabis users. We conducted a retrospective longitudinal cohort study of patients who received medical authorization to use cannabis from 2014 to 2019 in Ontario, matched (1:3 ratio) to population-based controls using propensity scores. Conditional Cox regressions were used to assess the association between cannabis authorization and the outcome. A total of 54,006 cannabis-authorized patients and 161,265 controls were analyzed. Approximately 39% were aged under 50 years, 54% were female, and 16% had a history of anxiety or mood disorders. The adjusted hazard ratio (aHR) for depressive disorders was 2.02 (95%CI: 1.83–2.22). The aHR was 2.23 (1.95–2.55) among subjects without prior mental health disorders. The interaction between sex (or age) and exposure was not significant. In conclusion, medical cannabis authorization was associated with an increased risk of depressive disorders. This finding highlights the need for a careful risk-benefit assessment when authorizing cannabis, particularly for patients who seek cannabis to treat a depressive condition. [ABSTRACT FROM AUTHOR]

Background: Some studies suggest cannabis use negatively affects tobacco cessation outcomes, but findings have been mixed. We examined whether cannabis use was associated with tobacco cessation outcomes in a real-world primary care setting.Methods: The analytic dataset consisted of 35,246 patients who enrolled between 2014 and 2016 in a primary care-based smoking cessation program in Ontario, Canada. Past 30-day cannabis use, for recreational or medical purposes, was self-reported at enrollment. Thirty-day point prevalence tobacco smoking abstinence was self-reported via online or telephone survey at 6 months post-enrollment.Results: Thirty days prior to enrollment, 79.9 % of patients had not used cannabis, 16.3 % used cannabis for recreational purposes only, and 3.8 % used cannabis for medical purposes. Unadjusted and adjusted odds of tobacco cessation at 6 months were reduced for patients using cannabis compared to non-users (ORs = 0.76-0.86, ps<0.05). When cannabis use was categorized by purpose, both unadjusted and adjusted odds of cessation were significantly lower for recreational users (ORs = 0.77-0.84, ps<0.05). Medical users had decreased odds of cessation in unadjusted analysis (OR = 0.74, 95 % CI = 0.61-0.89, p = 0.001), but not after adjustment for potential confounders. However, post-estimation contrasts did not indicate a significant difference between the effect of recreational and medical cannabis use.Conclusions: In a large real-world sample of patients seeking smoking cessation treatment, concurrent cannabis use was associated with decreased success with quitting smoking. Recreational cannabis use was consistently related to poorer cessation outcomes, but medical use was not. Additional research is needed to inform treatment strategies for this growing sub-population of smokers. [ABSTRACT FROM AUTHOR]