Association between non-medical cannabis legalization and emergency department visits for cannabis-induced psychosis

Clinical and public safety risks associated with cannabis legalization and frequency of cannabis use among forensic mental health patients

BACKGROUND

There are ongoing concerns regarding the impact of Canada's cannabis legalization and commercialization on vulnerable persons such as those with serious forms of mental illness, including persons with schizophrenia-spectrum disorders and users of forensic mental health services. The primary objective of this study was to investigate the potential harms and mental health-related impacts associated with cannabis legalization on a sample of forensic patients in Ontario (N = 187).

METHODS

Using a pseudo-prospective design, we investigated the frequency of cannabis use over a four-year period encompassing two years preceding and two years following the legislative change. We recorded clinical and public safety outcomes (i.e., mental health deterioration, length of stay in the forensic system, rates of hospital readmission, victimization and violence) over the same period to test relationships between these variables and rates of cannabis use.

RESULTS

We found that one-third of patients either self-reported or were discovered, via urine testing, to have used cannabis over the study period. Frequency of use was lower in the pre-legalization period, and then gradually and significantly increased after legalization. Compared to patients with no cannabis use, those with one or more instances of use were more likely to be readmitted to hospital and had higher rated static risk factors for violence. However, there were no observed differences in the actual rate of violence between patients using and not using cannabis, nor differences in the rate of violence over time. Over half of the patients who used cannabis experienced a worsening of their mental health status in the week following use.

CONCLUSIONS

Cannabis use among those with SMI is associated with adverse clinical outcomes. Results from this study suggest that the mental health burdens associated with cannabis use have risen in terms of delayed clinical recovery and progress through the forensic system since legalization.

"Like the Wild West": Health care provider perspectives on impacts of recreational cannabis legalization on patients and providers at a tertiary psychiatric hospital in Ontario, Canada

INTRODUCTION

Legalization has increased cannabis availability in Canada. Research shows complex relationships between cannabis use and mental health, and a need for health care providers to engage with patients about cannabis use. Providers have noted gaps in knowledge and research on the medical effects of cannabis as barriers to service delivery. It is unclear how providers and patients in mental health care settings have been impacted by legalization.

METHODS

From June 1 to July 2, 2021, we conducted a qualitative study involving semi-structured interviews with 20 health care providers in a range of roles (e.g., physicians, pharmacists, nurses) within a psychiatric hospital setting. Participants responded to open-ended questions with follow-up probes on various topics related to cannabis legalization. Topics included impacts on patient mental and physical health, clinical impacts, education and training, legal cannabis retail system and the medical cannabis access system.

RESULTS

Thematic analysis identified several themes in the data. Participants reported that legalization has had some positive impacts relating to clinical care and cannabis safety. They also expressed concerns with increased rates of cannabis use, risks to mental health and ongoing challenges engaging with patients about cannabis. Participants made recommendations for medical educators and regulators (e.g., updated curriculums, clinical guidelines), the mental health care sector (e.g., implementation of standardized screening), government (e.g., public health campaigns, safe use guidelines), the medical cannabis access system (e.g., increased regulation, research), and the legal cannabis system (e.g., zoning changes, point-of-sale information).

CONCLUSIONS

This study begins to address the paucity of data on impacts of legalization from mental health service delivery settings. Findings show that although legalization has had some positive impacts, there are ongoing patient concerns and unmet provider needs. More research is needed to understand the experiences of providers delivering care to populations experiencing mental health and/or substance use concerns who use cannabis in the post-legalization era.

Geographic clustering of cannabis stores in Canadian cities: A spatial analysis of the legal cannabis market 4 years post-legalisation

INTRODUCTION

Following the legalisation of non-medical cannabis in 2018, the number of cannabis stores in Canada has rapidly expanded with limited regulation on their geographic placement. This study characterised the clustering of cannabis stores in Canadian cities and evaluated the association of clustering with provincial policy and sociodemographic variables.

METHODS

Cross-sectional spatial analysis of cannabis store density in dissemination areas ('neighbourhoods', n = 39,226) in Canadian cities in September 2022. Cannabis store density was defined as the count of stores within 1000 m of a neighbourhood centre. Clusters of high-density cannabis retail were identified using Local Indicators of Spatial Autocorrelation. Associations between provincial policy (privatised vs. public market), sociodemographic variables and cannabis store density were evaluated using multivariable regression.

RESULTS

Clusters of high-density cannabis retail were identified in 86% of Canadian cities, and neighbourhoods in clusters had a median of 5 stores within 1000 m. Toronto, Canada's most populous city, had the most extreme clustering where neighbourhoods in clusters had a median of 10 stores (and a maximum of 25 stores) within 1000 m. Neighbourhoods in private versus public retail markets had a significantly higher neighbourhood-level density of cannabis stores (adjusted rate ratio [aRR] 63.37, 95% confidence interval [CI] 25.66-156.33). Lower neighbourhood income quintile was also associated with a higher neighbourhood-level density of cannabis stores (Q5 vs. Q1, aRR 1.28, 95% CI 1.17-1.40).

DISCUSSION AND CONCLUSIONS

Since cannabis was legalised, clusters of high-density cannabis retail have emerged in most Canadian cities and were more likely to form lower income neighbourhoods and in private retail markets.

The Züri Can study: Can regulated cannabis sales promote lower-risk cannabis use? Mini-review and study protocol

BACKGROUND AND AIMS

Recreational use of cannabis is illegal in most countries. Despite this, it is the third most commonly used psychoactive substance worldwide. As a result of this discrepancy, a growing number of countries have begun to reassess their legal approach to cannabis in recent years. While the health risks of cannabis and potential harm reduction measures are increasingly well understood, there are still significant gaps in knowledge about which regulatory and supply models are effective in promoting lower-risk cannabis use. In this paper, we outline the Züri Can study, which implements and evaluates a regulatory framework for cannabis sales in the city of Zurich, Switzerland, between 2023 and 2026. In addition, we illustrate how the study addresses current knowledge gaps to provide further insight into the potential future regulation of cannabis in Switzerland. To embed the study in the present scientific and political context, we first provide a brief overview of the state of knowledge on cannabis-related health risks and means of reducing them, along with lessons learned from other countries that have implemented varying regulatory systems.

DESIGN AND MEASUREMENTS

2,100 participants will be able to legally purchase cannabis either at a pharmacy, a cannabis social club, or the municipal drug information center over a three-year period. As part of this observational study, participants will be evaluated regarding their cannabis use habits and motives, their knowledge of lower-risk use, and their mental and physical health, among other parameters. Established harm reduction strategies are implemented as an integral part of the study design.

COMMENTS

The study will contribute to a better understanding of the impact of different cannabis distribution models on cannabis use patterns and related health outcomes. The results are expected to assist Swiss and international policy makers in developing evidence-based and public health-oriented regulatory frameworks for cannabis.

[Impact of the legalization of recreational cannabis on the risk of psychosis: A systematic review of the literature]

INTRODUCTION

Cannabis is the most consumed illicit substance in Europe. Although its sale and use remain generally prohibited, European public policies have evolved in recent years by legalizing cannabis for medical use and considering its legalization for recreational use. However, in the literature there are arguments in favor of a particular relationship between cannabis consumption and the development of psychotic symptoms. Thus, since cannabis consumption tends to increase with legalization, the aim of this review was to investigate the impact of the legalization of cannabis for recreational use on the risk of psychosis in regions of the world already concerned.

METHOD

A systematic review of the literature was carried out in April 2024 in the PubMed-Medline database according to PRISMA criteria. The sequence of keywords used was as follows: ("Cannabis" [Mesh] or cannabis) AND (("Psychotic Disorders" [Mesh] or Psychotic Disorders) or ("Schizophrenia Spectrum and Other Psychotic Disorders" [Mesh]) or ("Schizophrenia" [Mesh] or Schizophrenia)) AND legal use. The inclusion criteria applied for the selection of articles in this systematic review were: (1) any article investigating the potential impact of the legalization of cannabis for recreational use on the risk of psychosis (any type of psychosis diagnosed according to ICD-9, ICD-10, DSM-4 or DSM-5) by the intermediary of epidemiological (incidence or prevalence) and/or clinical (ambulatory consultations, emergency visits or hospitalizations) criteria, (2) any type of study (cross-sectional, longitudinal, prospective, retrospective, interventional and experimental) with a methodology including a temporal and/or geographic comparison of the risk of psychosis associated with the legalization of cannabis for recreational use with the exception of literature reviews and clinical cases descriptions, (3) absence of limitation for the age of the populations studied and for the date of publication, and (4) articles written in English or French. After evaluation by the two authors of the 160 articles identified, seven studies investigating the impact of the legalization of cannabis for recreational use on the risk of psychosis were included in this systematic literature review.

RESULTS

Four of the studies showed no increase in the use of health services for psychosis following the legalization of cannabis for recreational use whereas three other studies highlighted a negative impact of the legalization of cannabis for recreational use on the risk of psychosis. All of these studies were carried out in North America and were characterized by a low level of scientific evidence.

CONCLUSION

Given the complexity of assessing the impact of the legalization of cannabis for recreational use on the risk of psychosis, additional investigations through studies of better scientific quality are essential. However, based on the data already available, there is some evidence that there is a potential negative impact on mental health due to the legalization of cannabis for recreational use. In this context, in the event of legalization of cannabis for recreational use it seems essential to recommend lower risk use of cannabis (limit the frequency of use, delay the age of first consumption, control the THC content of products and promote prevention/education). Finally, in order to enable dynamic evolution of public health strategies the establishment of continued monitoring is essential as cannabis legalization evolves.

Changes in cannabis involvement in emergency department visits for anxiety disorders after cannabis legalization: a repeated cross-sectional study

Background

An increasing number of countries have or are considering legalizing cannabis. One concern is that legalization of cannabis will result in increased cannabis use and in turn a higher prevalence of anxiety disorders. We examined changes in emergency department (ED) visits for anxiety disorders with cannabis involvement in Ontario, over a period that involved medical and non-medical cannabis legalization.

Methods

This repeated cross-sectional population-based study identified all ED visits for anxiety disorders from residents of Ontario, Canada aged 10-105 between 2008 and 2022 (n = 15.7 million individuals). We used interrupted time series analyses to examine immediate and gradual changes in cannabis-involvement and alcohol-involvement (control condition) over four policy periods: medical cannabis legalization (January 2008-November 2015), expanded medical access (December 2015-September 2018), non-medical cannabis legalization with restrictions (October 2018-February 2020), and commercialization which overlapped with the COVID-19 pandemic (March 2020-December 2022). Poisson models were used to generate incidence rate ratios with 95% confidence intervals.

Findings

Over the 14-year study, there were 438,700 individuals with one or more ED visits for anxiety disorders of which 3880 (0.89%) individuals had cannabis involvement and 6329 (1.45%) individuals had alcohol involvement. During the commercialization/COVID-19 period monthly rates of anxiety disorders with cannabis-involvement were 156% higher (0.11 vs 0.29 per 100,000 individuals) relative to the pre-legalization period, compared to a 27% increase for alcohol-involvement (0.27 vs 0.35 per 1100,000 individuals). Rates of anxiety ED visits with cannabis involvement per 100,000 individuals increased gradually over the study period with no immediate or gradual changes after expanded medical access, legalization with restrictions or commercialization/COVID-19. However, during the commercialization/COVID-19 period there were large declines in total anxiety disorder ED visits and anxiety disorder ED visits with alcohol-involvement. Consequently, during this period there was an immediate 31.4% relative increase in the proportion of anxiety visits with cannabis-involvement (incidence rate ratio [IRR], 1.31; 95% CI 1.05-1.65).

Interpretation

We found large relative increases in anxiety disorder ED visits with cannabis involvement over a 14-year period involving medical and non-medical cannabis legalization. These findings may reflect increasing anxiety disorder problems from cannabis use, increasing self-medication of anxiety disorders with cannabis use, or both. The proportion of anxiety ED visits with cannabis involvement increased during the final period of the study but could have been the results of the market commercialization, COVID-19 or both and ongoing monitoring is indicated.

Funding

Canadian Institutes of Health Research (grant #452360).

A cross-sectional study of the relationship between frequency of cannabis use and psychiatric symptoms among people seeking mental health and addiction services in Nova Scotia (2019-21)

BACKGROUND

Cannabis use may be a modifiable risk factor for mental health problems; however, the role of cannabis use frequency in population seeking mental health and addiction services remains unclear. This study aimed to: 1) compare the prevalence and functional impact of psychiatric symptoms among frequent, infrequent, and non-users of cannabis; and 2) evaluate the associations between cannabis use frequency and functional impact of psychiatric symptoms in help-seeking individuals.

METHODS

Data from the Mental Health and Addictions (MHA) Central Intake system in Nova Scotia, Canada was used. Participants aged 19-64 who received MHA Intake assessments from September 2019 to December 2021 with complete information about substance use were included (N = 20,611). Cannabis use frequency over past 30 days was categorized into frequent (>4 times a month), infrequent (≤4 times a month), and non-use. Psychiatric symptomatology consists of five domains: mood, anxiety, psychosis, cognition, and externalizing behaviors. Multivariate ordinal logistic regression was used to examine the associations between cannabis use frequency and functional impact of psychiatric symptoms.

RESULTS

Frequent and infrequent cannabis users had a higher prevalence of psychiatric symptoms in each domain than non-users, while no significant differences were found between frequent and infrequent users. Frequent cannabis use was associated with greater functional impact of psychiatric symptoms in each domain compared to non-users, while infrequent use was only associated with greater functional impact of externalizing behaviors.

CONCLUSION

Frequent cannabis use is associated with increased prevalence and functional impact of psychiatric symptoms among adults seeking mental health services.

Neuromodulation for Cannabis Use: A Scoping Review

This scoping review explores the use of neuromodulation techniques in individuals with cannabis use. Our goal was to determine whether cannabis use alters cortical excitation and inhibition in the context of neuromodulation and to determine whether neuromodulation affects craving and cannabis use patterns. A systematic search was conducted using PubMed, OVID Medline, and PsycINFO from inception to 20 December 2022. Our review identified ten relevant studies, eight of which used Transcranial Magnetic Stimulation (TMS), while two employed Transcranial Direct Current Stimulation (tDCS). Findings from TMS studies suggest that cannabis users exhibit altered cortical inhibition, with decreased short interval intracortical inhibition (SICI) compared to non-users. Single sessions of rTMS did not have any impact on cannabis craving. By contrast, two studies found that multiple sessions of rTMS reduced cannabis use, but these changes did not meet the threshold for statistical significance and both studies were limited by small sample sizes. The two included tDCS studies found contradictory results, with one showing reduced cannabis craving with active treatment and another showing no effect of active treatment on craving compared to sham. Future studies should further explore the effects of multiple treatment sessions and different neuromodulation modalities.

The association between physical availability of cannabis retail outlets and frequent cannabis use and related health harms: a systematic review

An increasing number of regions have or are considering legalising the sale of cannabis for adult use. Experience from tobacco and alcohol regulation has found that greater access to physical retail stores is positively associated with increased substance use and harm. Whether this association exists for cannabis is unclear. We completed a systematic review examining the association between cannabis retail store access and adverse health outcomes. We identified articles up until July 20, 2023 by searching four databases. We included studies examining the association between measures of cannabis store access and adverse outcomes: frequent or problematic cannabis use, healthcare encounters due to cannabis use (e.g., cannabis-induced psychosis), and healthcare encounters potentially related to cannabis (e.g., self-harm episodes). Results were compared by study design type, retail access measure, and by subgroups including: children, adolescents, young adults, adults, and pregnant individuals. This review was registered with PROSPERO (CRD42021281788). The search generated 5750 citations of which we included 32 studies containing 44 unique primary analyses (unique retail measure and outcome pairs). Studies come from 4 countries (United States, Canada, Netherlands and Uruguay). Among the included analyses, there were consistent positive associations between greater cannabis retail access and 1) increased healthcare service use or poison control calls directly due to cannabis (10/12 analyses; 83%) (2) increased cannabis use and cannabis-related hospitalization during pregnancy (4/4; 100%) and 3) frequent cannabis use in adults and young adults (7/11; 64%). There was no consistent positive association between greater cannabis retail and increased frequent cannabis use in adolescents (1/4; 25%), healthcare service use potentially related to cannabis (2/6; 33%) or increased adverse neonatal birth outcomes (2/7; 26.8%). There is a positive association between greater cannabis store access and increases in cannabis harm. In countries with legal cannabis, retail restrictions may reduce use and harm.

Funding

Canadian Centre on Substance Use and Addiction (CCSA).

Impact of non-medical cannabis legalization with market restrictions on health service use and incident cases of psychotic disorder in Ontario, Canada

BACKGROUND

Cannabis is a risk factor in the onset and persistence of psychotic disorders. There is concern that non-medical cannabis legalization in Canada may have population-level impacts on psychotic disorders. We sought to examine changes in health service use and incident cases of psychotic disorder following cannabis legalization, during a period of tight restrictions on retail stores and product types.

METHODS

We conducted a cross-sectional interrupted time-series analysis using linked population-based health administrative data from Ontario (Canada) from January 2014 to March 2020. We identified psychosis-related outpatient visits, emergency department visits, hospitalizations, and inpatient length of stay, as well as incident cases of psychotic disorders, among people aged 14 to 60 years.

RESULTS

We did not find evidence of increases in health service use or incident cases of psychotic disorders over the short-term (17 month) period following cannabis legalization. However, we found clear increasing trends in health service use and incident cases of substance-induced psychotic disorders over the entire observation window (2014-2020).

CONCLUSION

Our findings suggest that the initial period of tight market restriction following legalization of non-medical cannabis was not associated with an increase in health service use or frequency of psychotic disorders. A longer post-legalization observation period, which includes expansion of the commercial cannabis market, is needed to fully understand the population-level impacts of non-medical cannabis legalization; thus, it would be premature to conclude that the legalization of non-medical cannabis did not lead to increases in health service use and incident cases of psychotic disorder.

Changes in Cannabis-Attributable Hospitalizations Following Nonmedical Cannabis Legalization in Canada

Importance

The impact of adult-use cannabis legalization and subsequent commercialization (ie, increasing store and product access) on hospitalizations in Canada is unclear.

Objectives

To examine changes in overall and subtypes of hospitalizations due to cannabis and associated factors following legalization in Canada and to compare changes between provinces.

Design, Setting, and Participants

This repeated cross-sectional analysis included all acute hospitalizations for individuals aged 15 to 105 years in Canada's 4 most populous provinces (Ontario, Quebec, Alberta and British Columbia, population 26.9 million individuals in 2018). Data were obtained from routinely collected health administrative databases. Immediate and gradual changes in the age- and sex-standardized rates of hospitalizations due to cannabis were compared using an interrupted time series design over 3 time periods: prelegalization (January 2015 to September 2018), legalization with product and store restrictions (October 2018 to February 2020), and commercialization, which overlapped with the COVID-19 pandemic (March 2020 to March 2021).

Main Outcomes and Measures

Rates of hospitalizations due to cannabis per 100 000 individuals and per 1000 all-cause hospital admissions.

Results

There were 105 203 hospitalizations due to cannabis over the 7-year study period, 69 192 of which (65.8%) were among male individuals, and 34 678 (33%) of which were among individuals aged 15 to 24 years. Overall, the age- and sex-standardized rate of hospitalizations increased 1.62 times between January 2015 (3.99 per 100 000 individuals) and March 2021 (6.46 per 100 000 individuals). The largest relative increase in hospitalizations was for cannabis-induced psychosis (rate ratio, 1.40; 95% CI, 1.34 to 1.47 during the commercialization period relative to the prelegalization period). Nationally, legalization with restrictions was associated with a gradual monthly decrease of -0.06 (95% CI -0.08 to -0.03) in hospitalizations due to cannabis per 100 000 individuals. Commercialization and the COVID-19 pandemic were associated with an immediate increase of 0.83 (95% CI, 0.30 to 1.30) hospitalizations due to cannabis per 100 000 individuals. There was provincial variation in changes, with provinces with less mature legal markets experiencing the greatest declines immediately following legalization.

Conclusions and Relevance

This cross-sectional study found that legalization with restrictions was not associated with an increase in hospitalizations due to cannabis but commercialization was. The findings suggest that commercialization of cannabis may be associated with increases in cannabis-related health harms, including cannabis-induced psychosis.