Cannabis legalization and cannabis use, daily cannabis use and cannabis-related problems among adults in Ontario, Canada (2001-2019)

Association of recreational cannabis legalization with changes in medical, illegal, and total cannabis expenditures in Canada

BACKGROUND

Recreational cannabis legalization (RCL) is being adopted by a growing number of jurisdictions internationally. RCL aims to displace the illegal cannabis market and has the potential to disrupt the medical market, yet few studies have examined these dynamics empirically.

METHODS

We used interrupted time series analysis to evaluate whether RCL (legislative passage in October 2017/implementation in October 2018) was associated with changes in quarterly national household expenditures on medical cannabis, illegal cannabis, and all cannabis types combined (licensed, illegal, and medical) in Canada from 2001 to 2023, adjusting for price fluctuations.

RESULTS

When RCL was passed, medical cannabis represented 11.8 % of the market and illegal cannabis 88.2 %. At five years post-RCL implementation, medical cannabis decreased to 3.7 %, illegal cannabis decreased to 24.3 %, and licensed cannabis took over 72.0 % of the market. The overall cannabis market increased in size by 75 % over these 5 years. Illegal cannabis expenditures increased between RCL passage and implementation but decreased immediately post-implementation and had a significant decreasing trend. Medical cannabis had a significant decreasing trend following RCL passage, and to a lesser extent following RCL implementation. Total cannabis expenditures increased immediately following RCL implementation and showed a significant increasing trend over time. Some caution should be used in interpreting these findings given uncertainty in data quality, particularly for illegal cannabis expenditures (and overall expenditures by extension).

CONCLUSIONS

Recreational cannabis legalization in Canada appears to be achieving one of its primary goals by displacing the illegal cannabis market, and medical users also appear to be transitioning to the recreational market. However, overall cannabis expenditures have also grown substantially since legalization, which could have adverse implications for public health.

Cannabidiol exerts teratogenic effects on developing zebrafish through the sonic hedgehog signaling pathway

The increasing legalization and decriminalization of cannabis for therapeutic and recreational purposes in various regions have influenced public perceptions and attitudes toward cannabidiol (CBD)-containing products, including their use during pregnancy. However, there is a knowledge gap regarding the effect of CBD on fetal development, and the mechanisms by which CBD induces developmental deficits have not been well studied. In this study, we investigated whether the teratogenic effects of CBD on developing zebrafish are mediated through Sonic hedgehog signaling (Shh), a critical pathway in development. Embryonic exposure to CBD reduced hatching and survival rates and suppressed Shh pathway activity, leading to decreased ptch2 expression-a regulatory receptor expressed in response to Shh signaling. Larval swimming activity was impaired by CBD exposure. However, coexposure to CBD and a synthetic Shh pathway activator significantly improved developmental outcomes, including decreased mortality, increased hatching rates, elevated ptch2 expression, and increased locomotor activity. These findings underscore the developmental risks associated with CBD use during pregnancy and highlight the involvement of the Shh signaling pathway in driving these effects. The results of this study can inform regulations for cannabis use during pregnancy and emphasize the need to develop therapeutic guidelines for the safe use of CBD-based treatments.

Risk of Dementia in Individuals With Emergency Department Visits or Hospitalizations Due to Cannabis

Importance

Cannabis use is associated with short-term memory impairment and long-term changes in brain structure; however, little is known about whether disordered cannabis use is associated with an increased risk of a dementia diagnosis.

Objective

To investigate the association between emergency department visits or hospitalizations (acute care encounters) due to cannabis and future dementia diagnosis.

Design, Setting, and Participants

Population-based, retrospective, matched cohort study using health administrative data from Ontario, Canada, between 2008 and 2021 (with follow-up until 2022) including all individuals aged 45 to 105 years living in Ontario who were eligible and did not have a diagnosis of dementia at cohort entry (2 620 083 individuals excluded).

Exposure

Individuals with incident acute care due to cannabis use, defined using International Classification of Diseases and Related Health Problems, Tenth Revision coding.

Main Outcomes and Measures

We used cause-specific adjusted hazard models to compare new diagnoses of dementia (from a validated algorithm) between individuals with acute care due to cannabis use with (1) individuals with all-cause acute care (excluding cannabis), (2) the general population, and (3) individuals with acute care due to alcohol use.

Results

The study included 6 086 794 individuals, of whom 16 275 (0.3%) had incident acute care due to cannabis use (mean age, 55.2 [SD, 8.3] years; 60.3% male). Annual rates of incident acute care due to cannabis use increased 5.0-fold in individuals aged 45 to 64 years (from 10.16 to 50.65 per 100 000) and 26.7-fold in individuals aged 65 years or older (from 0.65 to 16.99 per 100 000) between 2008 and 2021. Individuals with incident acute care due to cannabis use were at a 1.5-fold and 3.9-fold increased risk of dementia diagnosis within 5 years relative to individuals with all-cause acute care and the general population of the same age and sex, respectively (absolute rates of dementia diagnosis: 5.0% for cannabis-related acute care, 3.6% for all-cause acute care, and 1.3% in the general population). After adjustment for sociodemographics and chronic health conditions, individuals with acute care due to cannabis use remained at elevated risk relative to those with all-cause acute care (adjusted hazard ratio [aHR], 1.23; 95% CI, 1.09-1.39) and the general population (aHR, 1.72; 95% CI, 1.38-2.15). Individuals with acute care due to cannabis use were at lower risk than those with acute care due to alcohol use (aHR, 0.69; 95% CI, 0.62-0.76).

Conclusions and Relevance

Individuals with cannabis use severe enough to require hospital-based care were at increased risk of a new dementia diagnosis compared with those with all-cause hospital-based care or the general population. These findings have important implications considering increasing cannabis use among older adults.

Cannabis Use and Misuse Following Recreational Cannabis Legalization

Importance

An increasing number of jurisdictions have legalized recreational cannabis for adults, but most evaluations have used repeated cross-sectional designs, preventing examination of within-person and subgroup trajectories across legalization.

Objective

To examine changes in cannabis use and misuse in the 5 years following legalization in Canada both overall and by prelegalization cannabis use frequency using a longitudinal design.

Design, Setting, and Participants

This prospective cohort study included data from community-dwelling adults who participated in up to 11 biannual assessments from September 2018 to October 2023 in Ontario, Canada. Data were analyzed from November 2023 to January 2024.

Exposure

Five years of recreational cannabis legalization (baseline wave was immediately prior to legalization).

Main Outcome and Measures

Primary outcomes were cannabis use frequency and cannabis misuse, assessed using Cannabis Use Disorder Identification Test - Revised (CUDIT-R) score. Prelegalization cannabis use frequency, age, and sex were examined as moderators. Secondary outcomes included changes in cannabis product preferences over time.

Results

The final cohort included 1428 community-dwelling adults aged 18 to 65 years (859 [60.2%] female; mean [SD] age, 34.5 [13.9] years). Mean retention was 90% across all waves. Linear mixed-effects modeling found a significant increase in cannabis use frequency, such that the mean proportion of days using cannabis increased by 0.35% (95% CI, 0.19% to 0.51%) per year (P < .001) in the overall sample (1.75% over 5 years). In contrast, CUDIT-R scores (on scale of 0 to 32) decreased significantly overall (β = -0.08 [95% CI, -0.10 to -0.06] per year; -0.4 over 5 years; P < .001), most notably with the onset of the COVID-19 pandemic. Interaction analyses indicated that prelegalization cannabis use frequency significantly moderated changes for both outcomes (P < .001). Specifically, cannabis use and misuse decreased among prelegalization frequent consumers and modestly increased among occasional users and nonusers. Cannabis product preferences shifted away from dried flower, hashish, concentrates, oil, tinctures, and topicals to edibles, liquids, and vape pens.

Conclusions and Relevance

In this prospective cohort study of community-dwelling adults in Canada, cannabis use frequency increased modestly in the 5 years following legalization, while cannabis misuse decreased modestly. These changes were substantially moderated by prelegalization cannabis use, with more frequent consumers of cannabis before legalization exhibiting the largest decreases in both outcomes. Although longer-term surveillance is required, these results suggest Canadian recreational cannabis legalization was associated with modest negative and positive consequences among adults.

Cannabis Use in HIV: Impact on Inflammation, Immunity and the Microbiome

PURPOSE OF REVIEW

This review explores how cannabis impacts the gut microbiome, immune system, and ART outcomes in people with HIV (PWH). Given the increasing prevalence of cannabis use among PWH, we investigated its potential to reduce chronic inflammation and enhance gut health, both of which can influence HIV pathogenesis.

RECENT FINDINGS

Cannabis has immunomodulatory and anti-inflammatory effects, including reducing systemic inflammatory biomarkers (such as MCP-1 and IP-10) and improving gut barrier integrity through increased short-chain fatty acid (SCFA) production. Studies have shown that cannabis use is associated with increased gut mucosal immunity, decreased immune activation, and a unique microbiome composition. Preliminary evidence indicates that cannabis may influence HIV reservoirs, although the results remain inconclusive. Cannabis shows promise in managing inflammation, gut dysbiosis, and immune dysfunction in PWH. However, its effects on HIV reservoirs, adherence to antiretroviral therapy, and long-term outcomes need further investigation through rigorous clinical trials using standardized formulations.

Changes in Incident Schizophrenia Diagnoses Associated With Cannabis Use Disorder After Cannabis Legalization

Importance

Despite public health concerns that cannabis legalization may increase the number of cases of schizophrenia caused by cannabis, there is limited evidence on this topic.

Objective

To examine changes in the population-attributable risk fraction (PARF) for cannabis use disorder (CUD) associated with schizophrenia after liberalization of medical cannabis and legalization of nonmedical cannabis in Canada.

Design, Setting, and Participants

This population-based cohort study was conducted in Ontario, Canada, from January 1, 2006, to December 31, 2022, among 13 588 681 people aged 14 to 65 years without a history of schizophrenia.

Exposures

Diagnosis of CUD in the emergency department or hospital setting (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Canada [ICD-10-CA] codes F12x and T40.7).

Main Outcome and Measures

Changes in the PARF for CUD associated with schizophrenia (ICD-10-CA codes F20x and F25x and Diagnostic and Statistical Manual of Mental Disorders [Fourth Edition] [DSM-IV] code 295x) over 3 policy periods: prelegalization (January 2006 to November 2015), liberalization of medical and nonmedical cannabis (December 2015 to September 2018), and legalization of nonmedical cannabis (October 2018 to December 2022). A secondary outcome was diagnosis of psychosis not otherwise specified (NOS) (ICD-10-CA code F29x and DSM-IV code 298x). Segmented linear regression was used to examine changes after the liberalization of medical cannabis in 2015 and the legalization of nonmedical cannabis in 2018.

Results

The study included 13 588 681 individuals (mean [SD] age, 39.3 [16.1] years; 6 804 906 males [50.1%]), of whom 118 650 (0.9%) had CUD. A total of 91 106 individuals (0.7%) developed schizophrenia (80 523 of 13 470 031 [0.6%] in the general population without CUD vs 10 583 of 118 650 [8.9%] with CUD). The PARF for CUD associated with schizophrenia almost tripled from 3.7% (95% CI, 2.7%-4.7%) during the prelegalization period to 10.3% (95% CI, 8.9%-11.7%) during the legalization period. The PARF in the postlegalization period ranged from 18.9% (95% CI, 16.8%-21.0%) among males aged 19 to 24 years to 1.8% (95% CI, 1.1%-2.6%) among females aged 45 to 65 years. The annual incidence of schizophrenia was stable over time, while the incidence of psychosis NOS increased from 30.0 to 55.1 per 100 000 individuals (83.7%) in the postlegalization period relative to the prelegalization period. The PARF for CUD associated with schizophrenia increased steadily over the study with no accelerations after cannabis policy changes, while increases in the PARF for CUD associated with psychosis NOS accelerated after medical cannabis liberalization.

Conclusions and Relevance

In this cohort study of individuals aged 14 to 65 years in Ontario, Canada, the proportion of incident cases of schizophrenia associated with CUD almost tripled during a period of substantial liberalization of cannabis policy. Ongoing research is indicated to understand the long-term associations of cannabis policy with the prevalence of psychotic disorders.

"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.

Changes in prenatal cannabis-related diagnosed disorders after the Cannabis Act and the COVID-19 pandemic in Quebec, Canada

BACKGROUND AND AIMS

Public health concerns regarding pregnant women's health after the enactment of the Cannabis Act in Canada (CAC) (a law that allowed non-medical cannabis use), and the potential impact of the COVID-19 pandemic, call for a contemporary assessment of these two events. Our study measured associations between the CAC, the COVID-19 pandemic and the monthly prevalence rates of cannabis-, all drug- and alcohol-related diagnosed disorders among pregnant women in the province of Quebec.

DESIGN, SETTING AND PARTICIPANTS

This was a quasi-experimental design applying an interrupted time-series methodology in the province of Quebec, Canada. The participants were pregnant women aged 15-49 years, between January 2010 and July 2022.

MEASUREMENTS

Administrative health data from the Québec Integrated Chronic Disease Surveillance System were used to classify pregnant women according to cannabis-, all drug (excluding cannabis)- and alcohol-related disorders. The CAC (October 2018) and the COVID-19 pandemic (April 2020) were evaluated as (1) slope changes and (2) level changes. Cannabis-, all drug (excluding cannabis)- and alcohol-related disorders were measured by total monthly age-standardized monthly prevalence rate of each disorder for pregnant women aged 15-49 years.

FINDINGS

Before the CAC, the prevalence rate of cannabis-related diagnosed disorders significantly increased each month by 0.5% [95% confidence interval (CI) = 0.3-0.6] in the pregnant population. After the CAC, there were significant increases of 24% (95% CI = 1-53) of cannabis-related diagnosed disorders. No significant changes were observed for all drug (excluding cannabis)- and alcohol-related diagnosed disorders associated with the CAC. A non-significant decrease of 20% (95% CI = -38 to 3) was observed during the COVID-19 pandemic in alcohol-related disorders.

CONCLUSIONS

The monthly incidence rates of diagnosed cannabis-related disorders in pregnant women in Quebec increased significantly following the enactment of the Cannabis Act in Canada. Diagnoses of all drug (excluding cannabis)- and alcohol-related disorders remained relatively stable.

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).

Changes in medical cannabis use in Ontario, Canada (2014 to 2019): Trajectory of trends, medical authorization patterns and association with recreational cannabis legalization

Objectives

We characterized trends in medical cannabis use; examined characteristics associated with medical cannabis use without medical authorization; and examined the association between recreational cannabis legalization and medical cannabis use in Ontario, Canada.

Methods

Data were from a repeated, population-based, cross-sectional survey of adults (N = 19,543; 2014-2019). Cannabis use was categorized as either medical cannabis use, recreational cannabis use or no cannabis use. The analytical strategy included jointpoint regression, logistic regression and multinomial logistic regression.

Results

Medical cannabis use increased from 4 % to 11 % (Annual Percentage Change [APC]: 25 %, 95 % Confidence Interval [CI]: 17 %-33 %) and recreational cannabis use increased from 9 % to 15 % (APC: 9 %, 95 % CI: 3 %-15 %) between 2014 and 2019. Being 18 to 29 years old compared with being 65+ years old was associated with an increased likelihood of medical cannabis use without medical authorization (Odds Ratio [OR]: 4.05, 95 % CI: 2.12-7.72), while being of fair or poor self-perceived health compared with excellent, very good or good self-perceived health (OR: 0.61, 95 % CI: 0.40-0.95) was associated with a decreased likelihood of medical cannabis use without medical authorization. Recreational cannabis legalization was associated with an increased likelihood of medical cannabis use compared with no cannabis use (OR: 1.48, 95 % CI: 1.19-1.85) and of recreational cannabis use compared with no cannabis use (OR: 1.35, 95 % CI: 1.11-1.65).

Conclusions

Although medical cannabis use increased, it was largely used without medical authorization. Guidance and education that encourages medical usage under clinical supervision is recommended, and mitigation of known barriers to medical cannabis authorization.

Changes in modes of cannabis consumption pre- and post-legalization and their correlates among adults in Ontario, Canada: 2017-2022

Background: Despite an increase in the varieties of cannabis products available for consumption, limited evidence is available about the patterns of cannabis consumption methods before and after legalization.Objectives: To examine the changes in modes of cannabis use and their correlates among adults in Ontario, Canada both prior to and following cannabis legalization in 2018.Methods: Data were utilized from the 2017 to 2022 Centre for Addiction and Mental Health's (CAMH) Monitor study, a repeated cross-sectional survey of adults 18 years of age and older (n = 2,665; 56% male). The surveys employed a regionally stratified sampling design using computer-assisted telephone interviews and web surveys. Multinomial regression was performed to examine different modes of cannabis use.Results: The exclusive use of cannabis through ingestion methods increased from 4.0% in 2017 to 16.6% in 2022 (p < .001). However, the exclusive use of inhalation-based cannabis decreased from 49.4% in 2017 to 25.5% in 2022 (p < .001). Relative to inhalation-based modes, adults were about five times more likely to use ingestion-based modes in 2020 [RRR = 4.65 (2.94-7.35)] and 2022 [RRR = 4.75 (2.99-7.55)] than in 2019, after accounting for sociodemographic factors.Conclusions: Ingestion-based cannabis use among adults increased fourfold between 2017 and 2022, a period during which recreational cannabis use was legalized in Canada. The increase was especially evident after the legalization of cannabis edibles.

Risk-Taking, Social Support, and Belongingness Contribute to the Risk for Cannabis Use Frequency in University Students

Background: Cannabis use and misuse is known to be associated with a variety of negative health, academic, and work-related outcomes; therefore, it is important to study the factors that contribute to or moderate its use. Objectives: The aim of this study was to determine whether risky behavior, belongingness and social support as clustering variables play a role in cannabis use frequency. Method: In a university student sample, participant data on risky behavior, belongingness and social support were used to generate vulnerability profiles through cluster analysis (low vulnerability with low risk, low vulnerability with high belonging, moderate vulnerability, and high vulnerability). Using an analysis of variance, the vulnerability profiles were compared with respect to cannabis use frequency and quantity. Through chi-square tests we assessed whether these profiles are overrepresented in certain demographics. Results: The cluster analysis yielded four groups, which differed in their vulnerability for cannabis use. The most vulnerable cluster group had higher cannabis use frequency relative to the two least vulnerable groups. Low income vs. high income was also associated with high vulnerability group membership. International students were overrepresented in the low vulnerability with high belonging group relative to the low vulnerability with low-risk group. The opposite was observed for domestic students. Conclusions: This research adds to the expanding body of literature on cannabis use and misuse in Canada, which may contribute to public health policy and the prevention and treatment of cannabis addiction by providing new insight on who may be at risk.

How have cannabis use and related indicators changed since legalization of cannabis for non-medical purposes? Results of the Canadian Cannabis Survey 2018-2022

BACKGROUND

Cannabis use for non-medical purposes was legalized and regulated in Canada through the Cannabis Act in October 2018. This paper examined trends in use of cannabis for non-medical purposes and related indicators from pre- to post-legalization in Canada (2018-2022).

METHODS

Data from 5 years of the Canadian Cannabis Survey, an annual web-based survey administered to Canadians 16 years of age or older, were used in the analysis (n2018=12,952; n2019=11,922; n2020=10,821; n2021=10,733; n2022=10,048). Cannabis measures include questions about use, types of products, sources, risk perceptions and beliefs, and exposure to public education campaigns and health warnings. Adjusted logistic regression models tested differences in outcomes over time.

RESULTS

Past 12-month cannabis consumption increased among Canadians from 22 % in 2018 to 27 % in 2022 (AOR=1.41;99 % CI:1.28-1.54). Similarly, daily/almost daily (DAD) consumption increased from 5 % in 2018 to 7 % in 2022 (AOR=1.36;99 % CI:1.16-1.59). Consumption of dried flower, hash/kief, and concentrates/extracts (e.g., wax, shatter, budder) decreased since 2018, whereas consumption of edibles, beverages and vape pens/cartridges increased (p < 0.001). Legal purchasing increased from 4 % in 2018 to 69 % in 2022, while accessing cannabis through social and illegal sources decreased over time (p < 0.001).

CONCLUSION

More Canadians are reporting cannabis consumption since legalization and regulation of cannabis for non-medical purposes, continuing a pre-existing trend despite an increase in awareness of the risks of consuming cannabis. Trends in product use indicate a transition from dried flower and concentrates/extracts towards consumption of cannabis foods, drinks and vape pens/cartridges. The legal market is increasingly displacing the illicit cannabis market in Canada.

Marijuana use among community-dwelling older adults: A population-based study

OBJECTIVES

There is a paucity of population-level data on marijuana use and mental health and functioning in older adults.

METHODS

We analyzed cross-sectional data (n = 910) from a well-characterized cohort, the Monongahela-Youghiogheny Healthy Aging Team (MYHAT) study. MYHAT is an age-stratified random sample of the population age 65 years and older from a small-town in the USA. Half the sample was female and half were over 75 (Mean age = 77). Most participants were non-Hispanic White. Marijuana use was assessed by self-report and symptoms of mood disorders were screened using the modified Centers for Epidemiological Studies-Depression Scale and the Generalized Anxiety Disorder screener. Cognition was assessed by the Mini-Mental State Examination and a neuropsychological test battery; functioning using the OARS Activities of Daily Living and Instrumental Activities of Daily Living; and overall assessment using the Clinical Dementia Rating (CDR®).

RESULTS

One in five MYHAT participants had a history of marijuana use and 5% reported recent use, primarily for pain (41%) and recreation/relaxation (37%). Recent use was associated with cigarette and alcohol use, symptoms of depression or anxiety, and impairments in attention.

CONCLUSIONS

Twenty-percent of community-dwelling older adults living in a US state where recreational marijuana use is illegal had a history of marijuana use. Recent marijuana use was less common but, consistent with prior research, associated with other substance use and poorer mental health.

Cannabis use and incident atrial fibrillation in a longitudinal cohort

BACKGROUND

Cannabis use is increasing worldwide. While prior studies have reported an association between cannabis use and a higher risk of atrial fibrillation (AF), most were cross-sectional and generally relied on diagnostic coding to identify cannabis users, which may not be representative of the typical recreational cannabis user.

OBJECTIVE

The purpose of this study was to examine the association between recreational cannabis use and lifetime AF risk.

METHODS

We evaluated the AF risk of participants of the UK Biobank cohort who completed the cannabis use lifestyle questionnaire. Cannabis exposure was categorized as "Occasional Use" for less than 100 times used, "Frequent Use" for more than 100 times used, and "Never" users. AF events were identified using International Classification of Diseases codes. Cox models were used to estimate the hazard ratios (HRs) between cannabis use and incident AF and were subsequently adjusted for age, sex, race, alcohol, coffee, smoking, education, and baseline cardiovascular comorbidities.

RESULTS

A total of 150,554 participants (mean age 63.4 ± 7.7 years; 86,487 (57.4%) female; and 33,442 (22.2%) using cannabis at least once) were followed for a mean period of 6.1 ± 0.6 years. After multivariable adjustment, there were no statistically significant differences in incident AF among occasional users (HR 0.98; 95% confidence interval 0.89-1.08) nor frequent users (HR 1.03; 95% confidence interval 0.81-1.32) as compared with never users.

CONCLUSION

In a large prospective cohort study, there was no evidence that cannabis use was associated with a higher risk of incident AF. An evaluation of cannabis ingestion methods and quantification was not possible using the current data set.

Effects of cannabis legalisation on patterns of cannabis consumption among adolescents in Ontario, Canada (2001-2019)

INTRODUCTION

Cannabis legalisation was enacted on 17 October 2018 in Canada. Accordingly, the effects of cannabis legalisation on patterns of cannabis consumption were examined among adolescents, including on cannabis initiation, any cannabis use, daily cannabis use and cannabis dependence.

METHODS

Data from a biennial population-based, cross-sectional survey of students in Ontario were pooled in a pre-post design (2001-2019; N = 89,238). Participants provided self-reports of cannabis initiation, any cannabis use, daily cannabis use and cannabis dependence. Long-term trends in these patterns of cannabis consumption over two decades of observation were characterised to provide a broader context of usage. The effects of cannabis legalisation on patterns of cannabis consumption were quantified using logistic regression analyses.

RESULTS

Long-term trends over the two decades of observation indicated that cannabis initiation decreased and then increased (p = 0.0220), any cannabis use decreased and daily cannabis use decreased (p < 0.0001 and p = 0.0001, respectively) and cannabis dependence remained unchanged (p = 0.1187). However, in comparisons between the pre-cannabis legalisation period (2001-2017) and the post-cannabis legalisation period (2019), cannabis legalisation was not associated with cannabis initiation (odds ratio; 95% confidence interval 1.00; 0.79-1.27), but it was associated with an increased likelihood of any cannabis use (1.31; 1.12-1.53), daily cannabis use (1.40; 1.09-1.80) and cannabis dependence (1.98; 1.29-3.04).

DISCUSSION AND CONCLUSIONS

Cannabis legalisation was not associated with cannabis initiation, but it was associated with an increased likelihood of any cannabis use, daily cannabis use and cannabis dependence.

Using publicly available data to predict recreational cannabis legalization at the county-level: A machine learning approach

BACKGROUND

There is substantial geographic variability in local cannabis policies within states that have legalized recreational cannabis. This study develops an interpretable machine learning model that uses county-level population demographics, sociopolitical factors, and estimates of substance use and mental illness prevalences to predict the legality of recreational cannabis sales within each U.S. county.

METHODS

We merged data and selected 14 model inputs from the 2010 Census, 2012 County Presidential Data from the MIT Elections Lab, and Small Area Estimates from the National Surveys on Drug Use and Health (NSDUH) from 2010 to 2012 at the county level. County policies were labeled as having recreational cannabis legal (RCL) if the sale of recreational cannabis was allowed anywhere in the county in 2014, resulting in 92 RCL and 3002 non-RCL counties. We used synthetic data augmentation and minority oversampling techniques to build an ensemble of 1000 logistic regressions on random sub-samples of the data, withholding one state at a time and building models from all remaining states. Performance was evaluated by comparing the predicted policy conditions with the actual outcomes in 2014.

RESULTS

When compared to the actual RCL policies in 2014, the ensemble estimated predictions of counties transitioning to RCL had a macro f1 average score of 0.61. The main factors associated with legalizing county-level recreational cannabis sales were the prevalences of past-month cannabis use and past-year cocaine use.

CONCLUSION

By leveraging publicly available data from 2010 to 2012, our model was able to achieve appreciable discrimination in predicting counties with legal recreational cannabis sales in 2014, however, there is room for improvement. Having demonstrated model performance in the first handful of states to legalize cannabis, additional testing with more recent data using time to event models is warranted.

The effect of non-medical cannabis retailer proximity on use of mental health services for psychotic disorders in Ontario, Canada

BACKGROUND

Cannabis is associated with the onset and persistence of psychotic disorders. Evidence suggests that accessibility of substances is associated with an increased risk of use-related harms. We sought to examine the effect of residing in proximity to non-medical cannabis retailers on the prevalence of health service use for psychosis.

METHODS

We conducted a cross-sectional study using linked health administrative data, and used geospatial analyses to determine whether people in Ontario, Canada (aged 14-60 years) resided within walking (1.6 km) or driving (5.0 km) distance of non-medical cannabis retailers (open as of February-2020). We identified outpatient visits, emergency department (ED) visits, and hospitalizations for psychotic disorders between 01-April-2019 and 17-March-2020. We used zero-inflated Poisson regression models and gamma generalized linear models to estimate the association between cannabis retailer proximity and indicators of health service use.

RESULTS

Non-medical cannabis retailers were differentially located in areas with high levels of marginalization and pre-existing health service use for psychosis. People residing within walking or driving distance of a cannabis retailer had a higher rate of psychosis-related outpatient visits, ED visits, and hospitalizations, compared to people living outside these areas. This effect was stronger among those with no prior service use for psychosis.

CONCLUSIONS

Proximity to a non-medical cannabis retailer was associated with higher health service use for psychosis, even after adjustment for prior health service use. These findings suggest that opening of non-medical cannabis retailers could worsen the burden of psychosis on mental health services in areas with high-risk populations.

Behavioral economic analysis of legal and illegal cannabis demand in Spanish young adults with hazardous and non-hazardous cannabis use

BACKGROUND

In October 2021, a legal framework that regulates cannabis for recreational purposes in Spain was proposed, but research on its potential impacts on cannabis use is currently limited. This study examined the reliability and discriminant validity of two Marijuana Purchase Tasks (MPTs) for measuring hypothetical legal and illegal cannabis demand, and to examine differences in demand of both commodities in young adults at hazardous vs. non-hazardous cannabis use risk levels.

METHODS

A total of 171 Spanish young adults [Mage = 19.82 (SD = 1.81)] with past-month cannabis use participated in a cross-sectional study from September to November 2021. Two 27-item MPTs were used to estimate hypothetical demand for legal and illegal cannabis independently. The Cannabis Use Disorder Identification Test (CUDIT-R) was used to assess hazardous cannabis use and test for discriminant validity of the MPTs. Reliability analyses were conducted using Classical Test Theory (Cronbach's alpha) and Item Response Theory (Item Information Functions).

RESULTS

The MPT was reliable for measuring legal (α = 0.94) and illegal (α = 0.90) cannabis demand. Breakpoint (price at which demand ceases), and Pmax (price associated with maximum expenditure) were the most sensitive indicators to discriminate participants with different levels of the cannabis reinforcing trait. No significant differences between legal and illegal cannabis demand in the whole sample were observed, but hazardous vs. non-hazardous users showed higher legal and illegal demand, and decreased Breakpoint and Pmax if cannabis were legal vs illegal.

CONCLUSION

The MPT exhibits robust psychometric validity and may be useful to inform on cannabis regulatory science in Spain.

Cannabis legalization and driving under the influence of cannabis and driving under the influence of alcohol among adult and adolescent drivers in Ontario, Canada (2001-2019)

BACKGROUND

The impacts of cannabis legalization on driving under the influence of cannabis and driving under the influence of alcohol among adults and adolescents were examined in Ontario, Canada.

METHODS

Data were sourced from adult (N=38,479) and adolescent (N=23,216) populations-based surveys (2001-2019). The associations between cannabis legalization and driving within an hour of using cannabis and driving within an hour of drinking two or more drinks of alcohol were quantified using logistic regression, with testing of multiplicative interactions between cannabis legalization and age and sex. All analyses were conducted separately for adults and adolescents and restricted to participants with a valid driver's license.

RESULTS

Cannabis legalization was not associated with driving within an hour of using cannabis among adults (OR, 95% CI: 1.21, 0.69-2.11). However, a multiplicative interaction indicated that there was an increased likelihood of driving within an hour of using cannabis among adults ≥55 years of age (4.23, 1.85-9.71) pre-post cannabis legalization. Cannabis legalization was not associated with driving within an hour of using cannabis among adolescents (0.92, 0.72-1.16), or with driving within an hour of consuming two or more drinks of alcohol among adults (0.78, 0.51-1.20) or adolescents (0.87, 0.42-1.82).

CONCLUSIONS

An increased likelihood of driving under the influence of cannabis among adults ≥55 years of age was detected in the year following cannabis legalization, suggesting the need for greater public awareness and education and police monitoring and enforcement concerning driving under the influence of cannabis, particularly among older adults.

Analysis of Dispensing and Utilization Patterns of Medical Cannabis Products in State Licensed Cannabis Dispensaries

Background: To understand real-world dispensing and utilization patterns of medical cannabis (MC) and its financial impact on patients, we analyzed the database of a cannabis company licensed in New York state. Objectives: To evaluate the tetrahydrocannabinol (THC)/cannabidiol (CBD) dose ratios, association of various medical conditions to THC/CBD dose, and the cost of products in registered patients receiving MC from four licensed state dispensaries. Design: Retrospective analysis conducted on anonymized data between January 1, 2016 and December 31, 2020 listing 422,201 dispensed products from 32,845 individuals aged 18 years and older. Setting/Subjects: Adult patients with medical certification for cannabis use in New York, USA. Measurements: The database included patient's age, gender, qualifying medical condition, type and dose of product, medication directions, and amount of product dispensed. Results: Findings showed a median age of 53 years with 52% of patients female. Males were found to use more products than females (1.06:1). Pain (85%) was the most common medical condition and inhalation (57%) the most common route except when used for cancer-directed treatment and neurological conditions. Individuals received a median of six prescriptions costing a median of $50/product. Average THC:CBD ratios were 28:0.5 mg/day and 12:0.25 mg/dose. Neurological conditions demonstrated the highest average cost [mean (95% confidence interval {CI}): $73 ($71-$75)] and average CBD/dose per product [mean (95% CI): 5.89 (5.38-6.40)]. Individuals with a history of substance use disorder utilizing MC as an alternative substance displayed the highest average THC/dose [mean (95% CI): 14.25 (13.36-15.14)]. Conclusion: MC was utilized for various medical conditions with variability in THC:CBD ratio seen depending on the condition. Cost variation was also observed based on the individual's medical condition.

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.

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

A major public health concern of cannabis legalization is that it may result in an increase in psychotic disorders. We examined changes in emergency department (ED) visits for cannabis-induced psychosis following the legalization and subsequent commercialization (removal of restrictions on retail stores and product types) of non-medical cannabis in Ontario, Canada (population of 14.3 million). We used health administrative data containing the cause of all ED visits to examine changes over three periods; 1) pre-legalization (January 2014-September 2018); 2) legalization with restrictions (October 2018 - February 2020); and 3) commercialization (March 2020 - September 2021). We considered subgroups stratified by age and sex and examined cocaine- and methamphetamine-induced psychosis ED visits as controls. During our study, there were 6300 ED visits for cannabis-induced psychosis. The restricted legalization period was not associated with changes in rates of ED visits for cannabis-induced psychosis relative to pre-legalization. The commercialization period was associated with an immediate increase in rates of ED visits for cannabis-induced psychosis (IRR 1.30, 95% CI 1.02-1.66) and no gradual monthly change; immediate increases were seen only for youth above (IRR 1.63, 1.27-2.08, ages 19-24) but not below (IRR 0.73 95%CI 0.42-1.28 ages, 15-18) the legal age of purchase, and similar for men and women. Commercialization was not associated with changes in rates of ED visits for cocaine- or methamphetamine-induced psychosis. This suggests that legalization with store and product restrictions does not increase ED visits for cannabis-induced psychosis. In contrast, cannabis commercialization may increase cannabis-induced psychosis presentations highlighting the importance of preventive measures in regions considering legalization.

Cannabis Use Frequency and Cannabis-Related Consequences in High-Risk Young Adults Across Cannabis Legalization

Importance

A key concern about recreational cannabis legalization is increases in use and adverse consequences, particularly among young adults (aged 18-29 years) who have the highest prevalence of cannabis use, and especially in higher-risk, more vulnerable young adults. However, few longitudinal studies have examined patterns of cannabis consumption in high-risk young adults over the course of legalization.

Objective

To examine changes in cannabis use frequency and cannabis-related consequences over recreational cannabis legalization in Canada in a longitudinal sample of high-risk young adults.

Design, Setting, and Participants

Longitudinal observational cohort study following young adults in Ontario, Canada, aged 19.5 to 23.0 years who reported regular heavy episodic drinking (65% past-month cannabis use) at enrollment. Participants were surveyed every 4 months for 3 years between February 2017 and February 2020 (3 prelegalization waves, 4 postlegalization waves). Data were analyzed from March to May 2023.

Exposures

Recreational cannabis legalization in Canada and 4 potential moderators of change: sex, income, education, and prelegalization cannabis use frequency.

Main Outcomes and Measures

Cannabis use frequency and cannabis-related adverse consequences.

Results

In a cohort of 619 high-risk young adults (baseline mean [SD] age, 21.0 [1.2] years; 346 female participants [55.9%]), omnibus model testing revealed significant overall decreases in both cannabis use frequency (F = 2.276, 3000.96; P = .03) and cannabis-related consequences (F = 10.436, 3002.21; P < .001) over time, but these changes were substantially moderated by prelegalization frequency (frequency: F = 7.5224, 3021.88; P < .001; consequences: F = 7.2424, 2986.98; P < .001). Follow-up tests showed individuals who used cannabis more frequently prelegalization significantly decreased their use and cannabis-related consequences postlegalization. In contrast, individuals who did not use cannabis prelegalization exhibited a small magnitude increase in frequency over time but nonsignificant changes in cannabis-related consequences. Sex, income, and education did not moderate changes over time.

Conclusions and Relevance

In this cohort study of high-risk young adults, individuals using cannabis frequently prelegalization showed significant reductions in use and consequences over time, reflecting an aging out pattern. Small increases in use among participants with no prelegalization use were observed over time, but without parallel changes in cannabis-related consequences. The results did not reveal substantive adverse near-term outcomes across the legalization period, although a within-participants design cannot rule out the possibility of alternative trajectories in the absence of legalization.

Cannabis-Involved Traffic Injury Emergency Department Visits After Cannabis Legalization and Commercialization

Importance

The impact of nonmedical cannabis legalization on traffic injuries and cannabis involvement in traffic injuries is unclear.

Objective

To examine changes in the number and characteristics of cannabis-involved traffic injury emergency department (ED) visits from before to after legalization and subsequent commercialization (ie, increased retail store and product availability) of cannabis in Ontario, Canada.

Design, Setting, and Participants

This repeated cross-sectional study examined changes in cannabis- and alcohol-involved traffic injury ED visits in Ontario, Canada, during 3 time periods: prelegalization (January 2010-September 2018), legalization with product and retail store restrictions (October 2018-February 2020), and commercialization with new products and expanded number of stores, which coincided with the COVID-19 pandemic (March 2020-December 2021). All individuals aged 16 years and older eligible for Ontario's Universal Health Coverage were included. Season- and time-adjusted quasi-Poisson models were used to generate rate ratios with 95% CIs. Data were analyzed from March to April 2023.

Main Outcomes and Measures

Quarterly counts of cannabis-involved ED visits for traffic injury.

Results

There were 947 604 traffic injury ED visits, of which 426 (0.04%) had documented cannabis involvement and 7564 (0.8%) had documented alcohol involvement. Of the 418 individuals with documented cannabis involvement, 330 (78.9%) were male, 109 (25.6%) were aged 16 to 21 years (mean [SD] age at visit, 30.6 [12.0] years), and 113 (27.0%) had an ED visit or hospitalization for substance use in the 2 years before their traffic injury ED visit. Annual rates of cannabis-involved traffic injury ED visits increased 475.3% over the study period (0.18 visits per 1000 total motor vehicle collisions in 2010 to 1.01 in 2021). Over the same period, alcohol-involved traffic injury ED visits increased by 9.4% (8.03 in 2010 to 8.79 per 1000 traffic injury ED visits in 2021). Legalization with restrictions was associated with a 94% increase in the quarterly rate of cannabis involvement in traffic injury ED visits relative to prelegalization (adjusted rate ratio [aRR], 1.94; 95% CI, 1.37-2.75). Commercialization/COVID-19 was associated with a greater increase of 223% in rates (aRR, 3.23; 95% CI, 2.42-4.33). After adjusting for time trends before legalization, only commercialization/COVID-19 was associated with increased rates. Male sex (adjusted odds ratio [aOR], 3.38; 95% CI, 2.66-4.29), living in the lowest-income neighborhood (aOR, 1.92; 95% CI, 1.39-2.67), being aged 19 to 21 years (aOR, 4.67; 95% CI, 3.27-6.67), and having a prior cannabis-related ED visit (aOR, 8.03; 95% CI, 5.85-11.02) were all positively associated with cannabis involvement during a traffic injury ED visit.

Conclusions and Relevance

This cross-sectional study found large increases in cannabis involvement in ED visits for traffic injury over time, which may have accelerated following nonmedical cannabis commercialization. Although the frequency of visits was rare, they may reflect broader changes in cannabis-impaired driving. Greater prevention efforts, including targeted education and policy measures, in regions with legal cannabis are indicated.

Impacts of recreational cannabis legalization on use and harms: A narrative review of sex/gender differences

Legalization of cannabis use for non-medical (recreational) purposes is changing the global cannabis landscape. As attitudes toward cannabis use become more positive and prevalence of use increases in complex ways, concerns emerge about the potential for increased cannabis-attributable harms. Understanding the who, why, and when of this likely increase in cannabis-attributable harms is thus an important public health priority. Both sex and gender contribute to variability in the use, effects, and harms of cannabis and thus sex/gender considerations are important when evaluating the impacts of cannabis legalization. The goal of this narrative review is to broadly discuss sex/gender differences in attitudes toward and prevalence of cannabis use, whether there are sex/gender differences in the impacts of cannabis legalization, and why these sex/gender differences might exist. One of our strongest conclusions is that men have always been more likely to use cannabis than women, yet the sex/gender gap in prevalence of cannabis use has narrowed over time, and this might be partly due to cannabis legalization. The existing evidence suggests that there have also been sex/gender differences in the impacts of legalization on cannabis-attributable harms such as cannabis-involved motor vehicle collisions and hospitalizations, though these results are more variable. The body of literature reviewed has focused almost exclusively on samples of cisgender research participants, and thus future research should encourage inclusion of transgender and gender-diverse participants. More consideration of sex- and gender-based analysis in research evaluating long-term impacts of cannabis legalization is a clear research priority.