Perceptions of the health risks of cannabis: estimates from national surveys in Canada and the United States, 2018-2019

Regular cannabis use modulates gamma activity in brain regions serving motor control

BACKGROUND

People who regularly use cannabis exhibit altered brain dynamics during cognitive control tasks, though the impact of regular cannabis use on the neural dynamics serving motor control remains less understood.

AIMS

We sought to investigate how regular cannabis use modulates the neural dynamics serving motor control.

METHODS

Thirty-four people who regularly use cannabis (cannabis+) and 33 nonusers (cannabis-) underwent structured interviews about their substance use history and performed the Eriksen flanker task to map the neural dynamics serving motor control during high-density magnetoencephalography (MEG). The resulting neural data were transformed into the time-frequency domain to examine oscillatory activity and were imaged using a beamforming approach.

RESULTS

MEG sensor-level analyses revealed robust beta (16-24 Hz) and gamma oscillations (66-74 Hz) during motor planning and execution, which were imaged using a beamformer. Both responses peaked in the left primary motor cortex and voxel time series were extracted to evaluate the spontaneous and oscillatory dynamics. Our key findings indicated that the cannabis+ group exhibited weaker spontaneous gamma activity in the left primary motor cortex relative to the cannabis- group, which scaled with cannabis use and behavioral metrics. Interestingly, regular cannabis use was not associated with differences in oscillatory beta and gamma activity, and there were no group differences in spontaneous beta activity.

CONCLUSIONS

Our findings suggest that regular cannabis use is associated with suppressed spontaneous gamma activity in the left primary motor cortex, which scales with the degree of cannabis use disorder symptomatology and is coupled to behavioral task performance.

Associations between noticing public health education campaigns about cannabis and risk perceptions in the northern Canadian territories: a cross-sectional study

This study investigated whether noticing cannabis education campaigns was associated with increased cannabis risk perceptions in Canada's three territories following non-medical cannabis legalization. Data were from the Cannabis Policy Study in the Territories, including 2452 participants, age ≥16 years residing in Yukon, Northwest Territories and Nunavut. Poisson regression with robust standard errors were used to estimate associations between noticing cannabis education campaigns and moderate to very high risk perceptions of daily cannabis smoking, vaping, edible use and exposure to second-hand cannabis smoke, adjusting for sociodemographic characteristics and cannabis-use frequency. Results were compared with associations with risk perceptions of daily alcohol consumption and cigarette smoking, not included in cannabis education campaigns. Interactions were examined between noticing education campaigns and age group and cannabis-use frequency. Cannabis education campaigns were noticed by 40.4% of respondents, with lower awareness among those with lower education and income. Noticing campaigns was associated with higher risk perceptions of daily cannabis smoking [adjusted risk ratio (RRadj) = 1.09, 95% confidence interval (CI): 1.02-1.16] and vaping (RRadj = 1.09, 95%CI: 1.02-1.16). Significant interactions were not found with age group or cannabis-use frequency. Findings are consistent with modest effects of cannabis education campaigns. Approaches are needed to increase reach of cannabis education campaigns, including among groups with lower education and income.

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.

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.

Substance Use and Educational Impacts in Youth With and Without Chronic Illness

INTRODUCTION

Alcohol, cannabis, and nicotine are commonly used psychoactive substances that affect adolescent neurocognition. Little is known about the educational impacts of their use on measures of educational performance, participation and problems, especially among youth with a chronic illness who may use these substances to alleviate stress and symptoms.

METHODS

Adolescents receiving general or subspecialty care were administered an electronic survey from 2016 to 2018. Data were analyzed in 2023. Using modified Poisson models, cross-sectional associations between past 12-month usage of alcohol, cannabis, and/or nicotine and educational impacts were estimated.

RESULTS

Among 958 adolescents (mean age 16.0 years (SD 1.3), 564 (58.9%) female gender, 445 (46.5%) in subspecialty care), 294 (30.7%), 220 (23.0%), and 126 (13.2%) reported past 12-month use of alcohol, cannabis, and nicotine respectively, while 407 (42.5%) reported ≥1 educational impact, including recent lower grades 210 (21.9%), past 3-month truancy from school 164 (17.1%) or activities 170 (17.7%), and detention 82 (8.6%). Use of cannabis, but not other substances, was associated with negative educational impacts: lower grades (mostly C's/D's/F's), adjusted prevalence ratios [APR, (95% CI)] 1.54 (1.13-2.11); past 3-month truancy from school [2.16 (1.52-3.07)]; detention [2.29 (1.33-3.94)]. The association between cannabis use and any negative educational impact was stronger among adolescents with a chronic illness (p<0.001).

CONCLUSIONS

Among adolescents, cannabis use was associated with a heightened risk of negative educational impacts, even after controlling for alcohol and nicotine use. Adolescents with chronic illness were especially likely to experience negative educational impacts. Findings underscore need for preventive interventions and messaging to reduce risks.

A systematic review of cannabis health warning research

Background

Cannabis legalization provides an opportunity to communicate with consumers through mandated health warnings on cannabis packaging. However, research on cannabis health warnings is a nascent field. Therefore, a review is needed to synthesize cannabis health warning research and inform ongoing policy discussions.

Methods

This paper used systematic review guidelines to search online databases, including PubMed Central, Scopus, Web of Science, Jstor, Communication and Mass Media Complete, Medline, PsycINFO, and Google Scholar. Search strings combined the terms "cannabis" or "marijuana" with "health warning" or "health warning message" or "warning label" or "health warning label" or "health information label." Results were synthesized narratively.

Results

The search identified 90 research articles. After screening, 17 studies on the impact of cannabis health warnings were retained. Retained studies focused on the hypothetical effects of cannabis health warnings (n = 11; 64.7 %) and "real world" effects of implementing warnings post-legalization (n = 6; 35.3 %). Evidence indicated mandated cannabis health warnings improved noticing and recall of health warning content. Cannabis health warnings describing risks of addiction were consistently rated the least effective. Pictorial cannabis health warnings generally outperformed text-only warnings when displayed on their own, while experiments with warnings on products had mixed results. Cannabis health warnings decreased product appeal, mainly when package branding was minimized.

Conclusions

Health warnings on cannabis packaging are an important strategy to communicate risk to consumers. Mandating warnings increased notice, recall, and health knowledge. Warnings with pictures and describing specific risks were most effective, as was showing warnings without product branding.

Screening for cannabis use disorder among young adults: Sensitivity, specificity, and item-level performance of the Cannabis Use Disorders Identification Test - Revised

The Cannabis Use Disorders Identification Test Revised (CUDIT-R) is a widely used screening tool. However, its utility in screening for cannabis use disorder (CUD) among young adults requires further investigation. The current study evaluated the accuracy of the CUDIT-R in distinguishing between young adults with and without CUD. We also examined the individual item properties of the CUDIT-R in this sample. A community sample of young adults (N = 153, ages 19-26 years) who reported at least one lifetime period of regular cannabis use (i.e., twice or more per month for at least six months) completed the CUDIT-R and the Structured Clinical Interview for DSM-5 (SCID-5) Substance Use Module. The CUDIT-R showed good accuracy in distinguishing between young adults with and without CUD as determined by the SCID-5 (area under the receiver operating characteristic curve = 0.84). A cut-point of nine yielded 87.80 % sensitivity and 70.42 % specificity, with positive and negative predictive values of 77.42 % and 83.33 %, respectively. Item response theory analyses revealed that CUDIT-R items assessing impaired control, failure to meet expectations, time devoted to use, and memory and concentration problems displayed high discrimination and were relatively difficult, whereas items assessing frequency of use and attempts to reduce use showed moderate discrimination and relatively low difficulty. Items assessing hours high and use with potential for physical hazard displayed poor discrimination. The CUDIT-R appears to validly distinguish between young adults with and without CUD and may be useful in screening for CUD in this high-risk population. Further research considering individual item properties is needed to refine the CUDIT-R for use among young adults.

Emerging adult perceptions of cannabis consumption: Examining changes in perceptions from pre-legalization to post-legalization

BACKGROUND

Emerging adults (EAs) have the highest rates of cannabis consumption in Canada and are vulnerable to the potential impacts of frequent cannabis consumption. This study assessed EAs' perceived risk of cannabis consumption across multiple domains of potential harm based on the age (14-year-old, 21-year-old, or 28-year-old) and sex (male or female) of the vignette character, time-point (pre- or post-legalization), and participant's gender.

METHODS

Secondary analyses were conducted on data from a pre-legalization study and post-legalization replication. Participants included EAs between 18 and 25 years of age and living in Newfoundland and Labrador. Participants from the pre- and post-legalization studies were matched based on demographic variables and the assigned vignette character. Participants responded to seven items of perceived risk based on their assigned vignette character's (varied by age or sex) almost daily cannabis consumption.

RESULTS

Participants (N = 689) viewed cannabis consumption to have greater risks for a 14-year-old compared to a 21- or 28-year-old in all domains except for social life. Prior to legalization, participants who identified as a woman felt that cannabis had more detrimental impacts on social life than participants who identified as a man. Findings also suggested that pre-legalization cannabis consumption by a female was perceived as more detrimental to their social life than pre-legalization consumption by a male and post-legalization consumption by a female.

CONCLUSION

EAs do not fully appreciate the risks of cannabis consumption, suggesting that it is imperative for public health strategies to promote increased awareness of the risks of frequent cannabis consumption, and improve cannabis health literacy in this population.

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.

The development of a Cannabis Knowledge Assessment Tool (CKAT)

BACKGROUND

Misconceptions about the health risks of cannabis remain prevalent, indicating the need to improve public health messaging and determine the effectiveness of educational programming. Our objective was to develop a standardized questionnaire to measure knowledge about cannabis in the context of cannabis legalization.

METHODS

A Cannabis Knowledge Assessment Tool (CKAT) was created using the Delphi method. A purposive sample of healthcare professionals, policymakers, academics, patients, and students served as the content and development experts. Principal component analysis from the codes identified from open-ended feedback guided the item development. Upon completion, the CKAT was administered as a pre- and post-test in four schools (7th and 9th Grade) in Canada. The data were analysed to determine whether knowledge scores changed after participating in a cannabis education program.

RESULTS

Twenty-four experts initially participated in the Delphi process and 18 (75% retention) continued throughout. Principal component analysis identified 3 domains: 1) effects of cannabis on the individual, 2) general information about cannabis, and 3) cannabis harm reduction. The final questionnaire consisted of 16 multiple-true-false questions (64 items) and received a Flesch-Kincaid Grade Level of 6.3, and a SMOG index score of 7.6. The CKAT was completed by 132 students; seventy-three 7th grade and fifty-nine 9th grade students. The baseline mean CKAT score was 46.2 (SD:5.5), which increased to 50.7 (SD:4.6) after the cannabis educational program (p<0.05).

CONCLUSIONS

A novel tool to measure knowledge of cannabis was developed and piloted in 7th grade and 9th grade students. Future studies are required to test usability and validity of the CKAT in other contexts.

A study of self-reported personal cannabis use and state legal status and associations with engagement in and perceptions of cannabis-impaired driving

Objective: The objectives of the current study were to (1) characterize predictors of perceived risk of driving within 2 h of cannabis use and driving after cannabis use in a sample of adults who have used cannabis in the past year and (2) determine whether the influence of these predictors vary by state legalizations status.Methods: Data for this study were from online surveys. Study participants from Colorado, Iowa, and Illinois were included if they reported being between 25 and 40 years old and had a history of cannabis use. Outcome variables included (1) days of cannabis use per month, (2) reported driving within 2 h of cannabis use (vs. not driving within 2 h as reference), (3) proportion of driving after cannabis use days per month (days of driving a car within 2 h of cannabis use per month/days of cannabis use per month), and (4) perception of safety of driving after cannabis use. Potential predictors included age of first use of cannabis, gender, education status, and state of residence. The SAS GLMSELECT Procedure was used for the analysis.Results: Increased age of first use of cannabis was associated with decreased days of cannabis use per month (B = -0.51 days/month per year), a reduction in the proportion of driving after cannabis use days per month (B = -0.02 per month), and decreased perception of safety of driving after cannabis use (B = -0.06 per year). Female gender was also associated with less use (B = -2.3 days per month), a lower proportion of driving following use (B = -0.06 days driving/days used), and decreased perception of safety (B = -0.29). In addition, residents of Colorado reported using the most days, had the highest likelihood of driving within 2 h of use, and had the most positive perceptions of being able to safely drive after cannabis use.Conclusions: The delay in onset of cannabis use may mitigate its use among adults and driving after cannabis use. This has important implications for driver safety. Intervention programs for reducing cannabis's effects on driving should focus on individuals with early onset of use, male drivers, and drivers in states where cannabis for adult recreational use is legalized.

Prevalence and factors associated with self-reported exposure to secondhand cannabis smoke in the United States and Canada in 2019

Little is known about exposure to secondhand cannabis smoke (SHCS) among residents of detached single-family homes and multiunit housing (MUH). Using data from the 2019 International Cannabis Policy Study, the prevalence of (a) self-reported exposure to SHCS at home (n = 33,024) and (b) self-reported SHCS incursions into MUH (defined as SHCS from another unit/the outdoors, n = 15,634) was estimated in (1) Canada; (2) US states where non-medical cannabis use was legal, and (3) US states where it remained illegal. Factors associated with exposures and incursions were assessed using weighted logistic regression. Overall, 16.9% of residents in Canada, 20.6% in US legal states, and 15.5% in US illegal states reported exposure to SHCS in their homes at least once in the previous month. One quarter (25.7%) of Canadian MUH residents, 26.6% from US legal states, and 20.1% from US illegal states reported at least monthly incursions. Sociodemographic factors associated with incursions suggested MUH residents reporting incursions lived in qualitatively different MUH than those not reporting incursions. Irrespective of the legality of non-medical cannabis use, smoke-free policies in MUH should protect residents from involuntary exposure to all types of secondhand smoke.