The Potential Impact of Recreational Cannabis Legalization on the Prevalence of Cannabis Use Disorder and Psychotic Disorders: A Retrospective Observational Study

Abstract

Objectives: The principal objective of our study was to document the short-term impact of the legalization of recreational cannabis on active cannabis use, cannabis use disorder, and various psychotic disorders. Methods: We carried out a retrospective observational study of patients who were at least 12 years old and who had visited a psychiatrist in the emergency unit of the Centre hospitalier universitaire de Sherbrooke (CHUS). We included all the consultations of this type over a 5-month period, immediately following the legalization of recreational cannabis in Canada. We then divided our population into an adult (over 18) and teenager group (12 to 17) compared the data to the data from consultations made 2 years earlier, using a generalized linear mixed model. Results: We examined consultations in patients over 18 years old in prelegalization ( n = 1,247) and postlegalization ( n = 1,368) groups. We observed a statistically significant increase in the use of cannabis (28.0% to 37.1%; odds ratio [ OR] = 1.81 [1.34 to 2.44], P = 0.00011) as well as an increase in diagnoses of active cannabis use disorder (17.7% to 24.3%; OR = 1.53 [1.13 to 2.08], P = 0.0064). The increase in cannabis use disorder was more prominent among patients between 18 and 24 years old (17.3% to 25.9%; OR = 2.27 [1.17 to 4.40], P = 0.015). We observed no statistically significant difference in terms of psychotic disorder diagnoses (27.4% to 29.2%; OR = 1.17 [0.84 to 1.63], P = 0.35)]. Conversely, we identified a greater proportion of patients who had a personality disorder diagnosis in the postlegalization period (39.6% to 44.9%; OR = 1.35 [1.02 to 1.80], P = 0.038). Examination of pediatric (under 18 years old) consultations revealed no statistically significant differences. Conclusion: Although an affirmative conclusion is tentative, the current findings suggest a first link between the legalization of cannabis in Canada and increased diagnoses of cannabis use disorder, as well as cannabis use in general among patients in a university hospital psychiatric emergency department.

Associations Between Canada's Cannabis Legalization and Emergency Department Presentations for Transient Cannabis-Induced Psychosis and Schizophrenia Conditions: Ontario and Alberta, 2015–2019

“…Our null results appear similar to those described in a recent medical-chart-review study comparing the prevalence of pre- versus post-legalization psychotic-disorder presentations ( n ≈ 741) occurring 2 years before and 5 months after legalization to two Sherbrooke, Québec psychiatric emergency department units, with the Sherbrooke-based study finding no evidence of any significant difference in the pre- versus post-legalization prevalence of a psychotic-disorder diagnosis in patients’ medical records. 30 As the authors noted, however, the comparison of the prevalence of pre- versus post-legalization psychotic-disorder presentations may have been confounded by treatment-service changes occurring during the study period via the initiation of new community-based psychiatric-treatment outreach programs [i.e., new availability of intensive psychiatric follow-ups services in the community; creation of a specialized first-episode (FEP) psychosis team], and such alterations may have differentially affected patterns of psychotic-disorder presentations to the psychiatric ED study sites across the pre- and post-legalization periods. 30 In relation to the current study, a number of factors may have contributed to the null results related to our target series.…”

“… 30 As the authors noted, however, the comparison of the prevalence of pre- versus post-legalization psychotic-disorder presentations may have been confounded by treatment-service changes occurring during the study period via the initiation of new community-based psychiatric-treatment outreach programs [i.e., new availability of intensive psychiatric follow-ups services in the community; creation of a specialized first-episode (FEP) psychosis team], and such alterations may have differentially affected patterns of psychotic-disorder presentations to the psychiatric ED study sites across the pre- and post-legalization periods. 30 In relation to the current study, a number of factors may have contributed to the null results related to our target series. First, key indicators of patterns of cannabis use in Alberta and Ontario showed relatively little change after legalization.…”

Developments and Changes in Primary Public Health Outcome Indicators Associated with the Legalization of Non-Medical Cannabis Use and Supply in Canada (2018): A Comprehensive Overview

“…It also found an increase in diagnoses of cannabis use disorder (17.7 to 24.3%; see source study for diagnostic standards) among adults but not underage patients. There were no differences in diagnoses of psychotic disorders (27.4 to 29.2%) but a greater proportion presented with a personality disorder (39.6 to 44.9%) after legalization (Vignault et al, 2021 ).…”

Changes in health harms due to cannabis following legalisation of non‐medical cannabis in Canada in context of cannabis commercialisation: A scoping review

“…Four studies examined changes in cannabis use disorder or harmful cannabis use (heavy cannabis use or cannabis use during pregnancy) following legalisation (Table 5) [8,25,34,35]. Studies examined multiple subgroups (pregnant women, general population, individuals seeking outpatient addiction services and individuals presenting at a psychiatric ED).…”

“…Studies examined multiple subgroups (pregnant women, general population, individuals seeking outpatient addiction services and individuals presenting at a psychiatric ED). All studies used different measures of cannabis use with two studies using a validated tool for cannabis use disorders (Cannabis Use Disorders Identification Test-Revised, where a score of eight or greater constitutes problematic use and takes frequency of use, quantity used and severity of misuse into account and Severity of Dependence Scale, which assesses the psychological components of dependence, including anxieties about drug use) [8,34] and one study using a diagnosis of cannabis use disorder [35]. One study (n = 2615) found a significant increase in the prevalence of diagnosed cannabis use disorder in adults presenting to a psychiatric ED in Quebec 6 months following legalisation [35].…”