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Canada’s cannabis legalization and drivers’ traffic-injury presentations to emergency departments in Ontario and Alberta, 2015-2019
Abstract
Background
Worldwide momentum toward legalization of recreational cannabis use has raised a common concern that such policies might increase cannabis-impaired driving and consequent traffic-related harms, especially among youth. The current study evaluated this issue in Canada.
Methods
Utilizing provincial emergency department (ED) records (April 1, 2015-December 31, 2019) from Alberta and Ontario, Canada, we employed Seasonal Autoregressive Integrated Moving Average (SARIMA) models to assess associations between Canada’s cannabis legalization (via the Cannabis Act implemented on October 17, 2018) and weekly provincial counts of ICD-10-CA-defined traffic-injury ED presentations. For each province (Alberta/Ontario), SARIMA models were developed on two driver groups: all drivers, and youth drivers (aged 14-17 years in Alberta; 16-18 years, Ontario).
Results
There was no evidence of significant changes associated with cannabis legalization on post-legalization weekly counts of drivers’ traffic-injury ED visits in: (1) Alberta, all drivers (n = 52,752 traffic-injury presentations), an increase of 9.17 visits (95% CI -18.85; 37.20; p = 0.52); (2) Alberta, youth drivers (n = 3,265 presentations), a decrease of 0.66 visits (95% CI -2.26; 0.94; p = 0.42); (3) Ontario, all drivers (n = 186,921 presentations), an increase of 28.93 visits (95% CI -26.32; 84.19; p = 0.30); and (4) Ontario, youth drivers (n = 4,565), an increase of 0.09 visits (95% CI -6.25; 6.42; p = 0.98).
Conclusions
Implementation of the Cannabis Act was not associated with evidence of significant post-legalization changes in traffic-injury ED visits in Ontario or Alberta among all drivers or youth drivers, in particular.
... Eight studies focused on the most populated provinces: Québec, Ontario, Alberta, and British Columbia [63][64][65][66][67][68][69][70]. Two studies collected data across two provinces: Leatherdale et al. [71] in Ontario and Québec, and Callaghan, Sanches et al. [72] in Ontario and Alberta. Additionally, one study focused on undergraduates in Atlantic Canada, though the sample included students from other provinces [73]. ...
... The second category encompassed twelve studies examining cannabis-related injuries and emergency department (ED) visits attributable to cannabis [53,62,64,72,74,77,81,83,84,86,87,93]. While most studies in this category examined the rates of ED visits since legalization, two examined trends related to vaping [53,62], and one study examined traffic injury presentations related to cannabis in EDs [72]. ...
... The second category encompassed twelve studies examining cannabis-related injuries and emergency department (ED) visits attributable to cannabis [53,62,64,72,74,77,81,83,84,86,87,93]. While most studies in this category examined the rates of ED visits since legalization, two examined trends related to vaping [53,62], and one study examined traffic injury presentations related to cannabis in EDs [72]. It is important to note that although two studies examined hospital visits during the COVID-19 pandemic [81,86], we grouped them with the ED visits, rather than the COVID-19 category because the primary focus was ED visits and cannabisrelated injuries. ...
Background
Canada legalized recreational cannabis in 2018, and one of the primary objectives of the Cannabis Act was to protect youth by reducing their access to cannabis and providing public education. Canada has the highest prevalence of cannabis use worldwide, particularly among youth and young adults under the age of 25. Cannabis use is linked with many adverse effects for youth and young adults including psychosis, anxiety, depression, respiratory distress, cannabinoid hyperemesis syndrome, and impaired cognitive performance. Despite the high prevalence of cannabis use and the evolution of policies in Canada and globally, significant knowledge and research gaps remain regarding youth and young adult cannabis use. The aim of this scoping review is to map the extent, nature, and range of evidence available on youth and young adult cannabis use in Canada since its legalization, in order to strengthen policies, services, treatments, training, and public education strategies.
Methods
Using a scoping review framework developed by Arksey and O’Malley, along with the PRISMA-ScR guidelines, we conducted a rigorous search in five academic databases: MEDLINE, Embase, APA PsycINFO, CINAHL and Web of Science Core Collection. We included empirical studies that collected data in Canada after the legalization of recreational cannabis (October 2018) and focused on youth or young adults < 30. Two reviewers independently screened articles in two stages and extracted relevant information from articles meeting the inclusion criteria.
Results
Of the 47 articles meeting our inclusion criteria, 92% used quantitative methods, 6% were qualitative, and 2% used a mixed-methods approach. Over two-thirds (68%) used secondary data. These studies were categorized into six focus areas: (1) prevalence, patterns, and trends, (2) cannabis-related injuries and emergency department (ED) visits, (3) rates and patterns during the pandemic, (4) perceptions of cannabis use, (5) prevention tools, and (6) cannabis-related offenses. Key findings from the studies reviewed include an increase in cannabis use among 18-24-year-olds post-legalization, with mixed results for youth under 18. ED visits for intentional and unintentional cannabis-related injuries have increased in young children and teens. Perception studies show a mix of concern and normalization of cannabis use. Though limited, prevention studies are promising in raising awareness. A decline in cannabis-related offenses was noted by one study. The review highlights several research gaps, including the need for more qualitative data, disaggregation of demographic data, intervention research, and comprehensive studies on the physical and mental health impacts of cannabis use among youth and young adults.
Conclusion
Maintaining a public health approach is critical, with a focus on reducing the high prevalence of cannabis use among youth and young adults. This involves implementing prevention strategies to minimize harms, enhancing public education, minimizing commercialization, reducing youth access to cannabis, promoting guidelines for lower-risk cannabis use and harm reduction strategies, and increasing training for healthcare providers.
... Of the 29 articles included in this review, eight focused on the legalization of medical cannabis [22][23][24][25][26][27][28][29], with respect to recreational cannabis, there were 13 papers that addressed the impact of its legalization with respect to traffic accidents [3,[30][31][32][33][34][35][36][37][38][39][40][41], two papers included both medical and recreational cannabis [42,43], and seven papers discussed the decriminalization and legalization of cannabis in general [8,[43][44][45][46][47][48]. ...
... Tables 3 and 4 list the studies that have addressed the impact of recreational cannabis legalization in relation to traffic accidents. Eleven studies have compared the effect of legalization at two time points, before and after legalization [3,[30][31][32][34][35][36][38][39][40][41], and six studies have compared states that have legalized recreational cannabis versus states that have not [3,33,37,[39][40][41]. Rotermann (2020) [35] t-test statistics. ...
... In relation to the legalization of recreational cannabis, seven studies have found an increase in traffic accidents in some of the states that legalized recreational cannabis after its legalization [3,31,32,34,36,38,41]. One study indicates increases after the opening of dispensaries [40], while two studies found no effect on road safety [30,39]. Meanwhile, of the studies that compared states that have legalized cannabis with those that have not, four found a greater effect in states that have legalized recreational cannabis [3,33,40,41], and two studies find no significant effect [37,39]. ...
Background:
Legalizing medical and recreational cannabis and decriminalizing this substance may have unanticipated effects on traffic safety. The present study aimed to assess the impact of cannabis legalization on traffic accidents.
Methods:
A systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) declaration of the articles included in the Web of Science (WoS) and Scopus databases. The number of papers included in the review was 29.
Results:
The results show that in 15 papers, there is a relationship between the legalization of medical and/or recreational cannabis and the number of traffic accidents, while in 5 papers, no such relationship is observed. In addition, nine articles indicate a greater number of risk behaviors related to driving after consumption, identifying young, male, and alcohol consumption together with cannabis as the risk profile.
Conclusions:
It can be concluded that the legalization of medical and/or recreational cannabis has negative effects on road safety when considering the number of jobs that affect the number of fatalities.
... Few studies have investigated differences in relative risk estimates when using biological samples or self-reported exposure data (see Asbridge et al for alcohol and cannabis) (see Khanjani, Mousavi, Dehghanian, et al 2017, for cannabis) and only one study used a combination of information from both sources. 11 25 Asbridge et al found that cannabis increases the risk of RTI in a model using exposure by blood samples but not selfreport data on cannabis, which was also observed by Khanjani et al. 14 Interestingly, combining blood and self-reports had a significant impact on estimates for cannabis but was negligible when both exposure measurements for alcohol were combined. 11 This has yet to be replicated. ...
... Because Mexico is undergoing changes in the legalisation/ decriminalisation of cannabis, we recommend further studies on the potential effects of cannabis legalisation on crash fatalities and injuries, as has been done in other countries in the region such as Uruguay 34 35 and Canada. 25 Using two sources of exposure in the hazard period has been reported before 11 14 in case-crossover. Combining self-report data for alcohol in our study increased the amount of information yet barely affected the estimates for alcohol as a risk factor for RTI, as reported by Asbridge. ...
Bacterkground
There is debate on whether cannabis affects road traffic injuries (RTIs) separately from the effects of alcohol. Our goals are to report the possible increase in risk of an RTI among alcohol and cannabis users by type of exposure (biological, self-reported and combined) and the possible interaction of alcohol and cannabis in patients with an RTI in an emergency department in Mexico City.
Methods
A case–crossover study with 433 cases of RTI (as a pedestrian, driver or passenger) during the period January–April 2022. A breath sample, an oral sample for cannabis detection and self-reported alcohol and cannabis use 6 hours prior to the RTI and in two control periods were used. We report ORs and 95% CIs from conditional logistic regressions for the case–crossover estimates.
Results
Alcohol alone increased the risk of an RTI (OR=6.02, 95% CI 3.29 to 10.99) for most RTIs, regardless of whether we used information from self-reports or a breath sample in the hazard period. Conversely, cannabis only increased the RTI when we added information in the hazard period from self-reports or oral samples. Nevertheless, this increase in risk disappeared (OR=2.06, 95% CI 0.90 to 4.70) among those who only used cannabis. We also found no evidence of interaction between alcohol and cannabis in the risk of an RTI.
Conclusions
Alcohol is the most commonly used substance in Mexico and a high-risk factor for RTI in Mexico City. Although cannabis alone was not associated with an RTI, continuous monitoring of its effects is required.
... [5][6][7][8] Two Canadian studies have also examined population-level changes in total traffic injury visits following legalization. 9,10 One study found no increase in traffic injury emergency department (ED) visits in Ontario and Alberta during the first year following legalization. Another study also found no increase in total traffic injury hospitalizations in Canada over 2.5 years following legalization. ...
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.
... In Oregon and Washington, 3 years after their respective CRULs were passed, no changes in traffic fatalities were observed compared to non-CRUL states where road traffic pre-conditions were similar [10,11]. In the Canadian provinces of Ontario and Alberta, enactment of CRULs was not found to be associated with significant changes in traffic injuries [12]. ...
Introduction:
In the past decade, a group of studies has begun to explore the association between cannabis recreational use policies and traffic crashes. After these policies are set in place, several factors may affect cannabis consumption, including the number of cannabis stores (NCS) per capita. This study examines the association between the enactment of Canada's Cannabis Act (CCA) (18 October 2018) and the NCS (allowed to function from 1 April 2019) with traffic injuries in Toronto.
Methods:
We explored the association of the CCA and the NCS with traffic crashes. We applied two methods: hybrid difference-in-difference (DID) and hybrid-fuzzy DID. We used generalised linear models using CCA and the NCS per capita as the main variables of interest. We adjusted for precipitation, temperature and snow. Information is gathered from Toronto Police Service, Alcohol and Gaming Commission of Ontario, and Environment Canada. The period of analysis was from 1 January 2016 to 31 December 2019.
Results:
Regardless of the outcome, neither the CCA nor the NCS is associated with concomitant changes in the outcomes. In hybrid DID models, the CCA is associated with non-significant decreases of 9% (incidence rate ratio 0.91, 95% confidence interval 0.74,1.11) in traffic crashes and in the hybrid-fuzzy DID models, the NCS are associated with nonsignificant decreases of 3% (95% confidence interval - 9%, 4%) in the same outcome.
Discussion and conclusions:
This study observes that more research is needed to better understand the short-term effects (April to December 2019) of NCS in Toronto on road safety outcomes.
... Four studies found a significant increase in traffic fatalities after RCL in the US and Uruguay [7][8][9][10], two found an increase in traffic fatalities after RCL only in certain states [11,12] and three did not report any significant changes in traffic fatality in US states after RCL [13,14]. Only one study has been done in Canada, which found no change in emergency department (ED) visits for non-fatal traffic injury after RCL [15]. ...
Aims:
To measure the impact of Canada's recreational cannabis legalization (RCL) in October 2018 and the subsequent impact of the COVID-19 lockdowns from March 2020 on rates of emergency department (ED) visits and hospitalizations for traffic injury.
Design:
An interrupted time series analysis of rates of ED visits and hospitalizations in Canada recorded in population-based databases from January/April 2010 to March 2021.
Setting:
ED visits in Ontario and Alberta and hospitalizations in Ontario, Alberta, British Columbia, Prairies [Manitoba, Saskatchewan], and Maritimes [Nova Scotia, New Brunswick, Newfoundland, Prince Edward Island]. Cases Monthly counts of presentations to the ED or hospital for motor vehicle injury or pedestrian/cyclist injury, used to calculate monthly rates per 100,000 population.
Measurements:
An occurrence of one or more International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Canada (ICD-10-CA) code for motor vehicle injury (V20-V29, V40-V79, V30-39, V86) and pedestrian/cyclist injury (V01-V09, V10-V19) within the National Ambulatory Care Reporting System and Discharge Abstract Database.
Findings:
There were no statistically significant changes in rates of ED visits and hospitalizations for motor vehicle or pedestrian/cyclist injury after RCL after accounting for multiple testing. After COVID-19, there was an immediate decrease in the rate of ED visits for motor vehicle injury that was statistically significant only in Ontario (level change ß = -16.07 in Ontario, 95% confidence interval [CI] -20.55 to -11.60, p=0.000; ß = -10.34 in Alberta, 95% CI -17.80 to -2.89, p=0.008; alpha of 0.004) and no changes in rates of hospitalizations.
Conclusions:
Canada's recreational cannabis legalization (RCL) did not notably impact motor vehicle and pedestrian/cyclist injury. The rate of emergency department visits for motor vehicle injury decreased immediately after COVID-19, resulting in rates below post-RCL levels in the year after COVID-19.
... For example, in the present study, the most recent national surveys indicate that 25% to 27% of Canadian adults use cannabis annually, 33 representing a 5% increase since the initial 2017 survey-and a 22% increase since the first Canadian cannabis survey in 1985. However, available public health data on changes in the prevalence of cannabis-related harms, such as cannabis-related traffic accidents 34,35 and emergency department visits for cannabis intoxication, [36][37][38][39] have been inconsistent. Given the evidence that there has been a clear increase in the prevalence of cannabis use postlegalization, this is a key contribution to ongoing appraisals of cannabis legalization in Canada. ...
Aims
To estimate temporal trends in cannabis consumption in the Canadian household population using national survey data and map changes in cannabis consumption postlegalization in 2018.
Methods
In a 2-step meta-analysis approach, we first analyzed each survey year separately by estimating the weighted past-year prevalence (%) of self-reported cannabis use (including just once) with its 95% confidence intervals (CIs). In the next step, to produce aggregate data for each survey year, we pooled prevalences using the DerSimonian and Laird random-effects (determined a priori) meta-analysis model packages in R to estimate the between-study variance (τ ² ) for the inverse variance method, and the Freeman-Tukey Double arcsine transformation.
Results
In total, 29 Statistics Canada survey iterations met eligibility for inclusion in the meta-analysis. Reported past-year prevalences for cannabis use ranged from 4.2% in 1993 to 27% in 2021. The overall prevalence of past-year cannabis use was 11.4% (95% CI, 9.7%–13.3%; 22 surveys; 53,712/474,888 participants; I ² =99.8%; τ ² =0.0048). There was a significant increase in cannabis past-year prevalence in subgroup meta-analyses ( P <0.0001) comparing postlegalization [2018–2021: 25.0% (95% CI, 23%–27%), I ² =96%] to prelegalization [1985–2017: 9.9% (95% CI, 9%–11%), I ² =99%]. There was also a significant time trend, with a steady increase in the reported past-year cannabis prevalence over time from 1985 through 2021. Notably, the most recent national estimate of cannabis prevalence from 2021 was nearly 6 times the first estimate from 1985 (27% vs. 5%).
Conclusions
The present study is the first to synthesize Canadian household survey data to estimate the temporal trends in cannabis consumption and is the first meta-analysis examining both the prevalence and changes postlegalization of cannabis use in Canada. The evidence indicates increasing past-year cannabis consumption and time, with a statistically significant increase postlegalization. The public health implications of these changes require further study.
Objectifs
Estimer les tendances temporelles de la consommation de cannabis dans les populations des ménages canadiens à l’aide de données d’enquêtes nationales et cartographier les changements dans la consommation de cannabis après la légalisation en 2018.
Méthodes
Dans une approche de méta-analyse en deux étapes, nous avons d’abord analysé chaque année d’enquête séparément en estimant la prévalence pondérée (%) au cours de la dernière année de la consommation de cannabis auto-déclarée (y compris une seule fois) dans ses intervalles de confiance à 95% (IC à 95%). Dans l'étape suivante, pour produire des données agrégées pour chaque année d’enquête, nous avons regroupé les prévalences à l’aide de la méthode d’effets aléatoires de DerSimonian et Laird (déterminé a priori) version de modèles de méta-analyse en R pour estimer la variance entre les études (2) pour la méthode de la variance inverse, et la transformation de Freeman-Tukey à double arc-sinus.
Résultats
Au total, 29 itérations de l’enquête de Statistique Canada répondaient aux critères d’admissibilité à l’inclusion dans la méta-analyse. Les prévalences de consommation de cannabis signalées au cours de l’année précédente variaient de 4,2% en 1993 à 27% en 2021. La prévalence globale de la consommation de cannabis au cours de l’année précédente était de 11,4% (IC à 95%, 9,7-13,3%; 22 enquêtes; 53 712/474 888 participants; I ² =99,8%; 2=0,0048). Il y a eu une augmentation significative dans la prévalence du cannabis au cours de l’année précédente dans les méta-analyses de sous-groupes (valeur p;0,0001) comparant les périodes post légalisation (2018–2021: 25,0% [IC à 95%, 23%–27%], I ² =96%) à la période pré-légalisation (1985–2017: 10% [IC à 95%, 9%–11%], I ² =99,3%). Une tendance temporelle significative a également été observée, avec une augmentation constante du nombre de cas de consommation de cannabis au cours de l’année écoulée, de 1985 à 2021. Il est à noter que l’estimation nationale la plus récente sur la prévalence du cannabis en 2021 était près de six fois la première estimation de 1985 (27% contre 5%).
Conclusions
La présente étude est la première à synthétiser les données d’enquêtes auprès des ménages canadiens afin d’estimer les tendances temporelles de la consommation de cannabis. C’est aussi la première méta-analyse examinant à la fois la prévalence et les changements après la légalisation de la consommation de cannabis au Canada. Les données indiquent une augmentation de la consommation de cannabis au cours de l’année écoulée, avec une augmentation statistiquement significative après la légalisation. Les implications de ces changements en matière de santé publique nécessitent une étude plus approfondie.
Objective:
We investigated associations between the retail distribution of recreational marijuana in Colorado and (i) past 30-day marijuana use and (ii) driving after marijuana use (DAMU) among a representative sample of public high school students using four waves of data from a state surveillance system.
Methods:
Past 30-day marijuana use was assessed among all sampled students (n = 85,336). DAMU was assessed among students 15 years or older who indicated driving (n = 47,518). Modified Poisson regression with robust variance estimates was used to estimate prevalence ratios (PR) comparing the pre-distribution (2013) and post-distribution (2015, 2017, 2019) periods for marijuana-related behaviors. Frequency of behavioral engagement was assessed using a multinomial approach.
Results:
An estimated 20.3% of students engaged in past 30-day marijuana use and 10.5% of student drivers engaged in DAMU. Retail distribution of recreational marijuana was not significantly associated with the prevalence of any marijuana use or DAMU. However, it was associated with 1.16 (95% CI: 1.04-1.29) times the prevalence of using marijuana one or two times in the last 30 days, 1.27 (1.03, 1.55) times the prevalence of DAMU one time, and 0.82 (0.69, 0.98) times the prevalence of DAMU six or more times. No significant associations were observed for the remaining frequency categories.
Conclusions:
Approximately 1 in 10 students who drive reported DAMU. Varying prevalence in the frequency of past 30-day marijuana use and DAMU was observed following the retail distribution of recreational marijuana in Colorado. Care should be taken to properly educate adolescent drivers regarding the dangers of DAMU.
Objective:
To determine the effect of recreational cannabis legalization (RCL) and/or recreational cannabis commercialization (RCC) on emergency department (ED) visits, hospitalizations, and deaths due to substance use, injury, and mental health among those aged 11 years and older.
Methods:
A systematic review of six electronic databases up to February 1, 2023. Original, peer-reviewed articles with interrupted time series or before and after designs were included. Four independent reviewers screened articles and assessed risk of bias. Outcomes with 'critical' risk of bias were excluded. Protocol registered on PROSPERO (# CRD42021265183).
Results:
After screening and risk of bias assessment, 29 studies were included which examined ED visits or hospitalizations for cannabis use or alcohol (N = 10), opioid mortality (N = 3), motor vehicle fatalities or injury (N = 11), and intentional injury/mental health (N = 5). Rates or number of cannabis-related hospitalizations increased after RCL in Canada and the USA. Immediate increases in rates of cannabis-related ED visits were found after both RCL and RCC in Canada. Rates of traffic fatalities increased after RCL and RCC in certain jurisdictions in the USA.
Conclusions:
RCL was associated with increased rates of cannabis-related hospitalizations. RCL and/or RCC was associated with increased rates of cannabis-related ED visits, consistently shown across sex and age groups. The effect on fatal motor vehicle incidents was mixed, with observed increases found after RCL and/or RCC. The effect of RCL or RCC on opioids, alcohol, intentional injury, and mental health is not clear. These results inform population health initiatives and international jurisdictions considering RCL implementation.
Aims:
We provide a narrative summary of research on changes in cannabis arrests, cannabis products and prices, cannabis use and cannabis-related harm since legalization.
Methods:
We systematically searched for research on the impacts of cannabis legalization in Canada in PubMed, Embase, Statistics Canada and government websites and Google Scholar, published between 2006 and 2021.
Results:
Cannabis legalization in Canada has been followed by substantial reductions in cannabis-related arrests and cannabis prices. It has also increased adults' access to a diverse range of cannabis products, including edibles and extracts. The prevalence of cannabis use among young adults has increased, but there have been no marked increases or decreases in use among high school students or changes in the prevalence of daily or near-daily use. Legalization has been associated with increased adult hospital attendances for psychiatric distress and vomiting, unintentional ingestion of edible cannabis products by children and hospitalizations for cannabis use disorders in adults. There is conflicting evidence on whether cannabis-impaired driving has increased since legalization. There is suggestive evidence that presentations to emergency departments with psychoses and cannabis use disorders may have increased since legalization.
Conclusions:
Legalization of cannabis in Canada appears to have reduced cannabis arrests and increased access to a variety of more potent cannabis products at lower prices. Since 2019, recent cannabis use in Canada has modestly increased among adults but not among adolescents. There is evidence of increased acute adverse effects of cannabis among adults and children.
Background:
Recreational cannabis policies are being considered in many jurisdictions internationally. Given that cannabis use is more prevalent among people with depression, legalisation may lead to more adverse events in this population. Cannabis legalisation in Canada included the legalisation of flower and herbs (phase 1) in October 2018, and the deregulation of cannabis edibles one year later (phase 2). This study investigated disparities in cannabis-related emergency department (ED) visits in depressed and non-depressed individuals in each phase.
Methods:
Using administrative data, we identified all adults diagnosed with depression 60 months prior to legalisation (n = 929 844). A non-depressed comparison group was identified using propensity score matching. We compared the pre-post policy differences in cannabis-related ED-visits in depressed individuals v. matched (and unmatched) non-depressed individuals.
Results:
In the matched sample (i.e. comparison with non-depressed people similar to the depressed group), people with depression had approximately four times higher risk of cannabis-related ED-visits relative to the non-depressed over the entire period. Phases 1 and 2 were not associated with any changes in the matched depressed and non-depressed groups. In the unmatched sample (i.e. comparison with the non-depressed general population), the disparity between individuals with and without depression is greater. While phase 1 was associated with an immediate increase in ED-visits among the general population, phase 2 was not associated with any changes in the unmatched depressed and non-depressed groups.
Conclusions:
Depression is a risk factor for cannabis-related ED-visits. Cannabis legalisation did not further elevate the risk among individuals diagnosed with depression.
Introduction:
The legalisation of cannabis in Canada in 2018, and subsequent increase in prevalence of use, has generated interest in understanding potential changes in problematic patterns of use, including by socio-demographic factors such as race/ethnicity and neighbourhood deprivation level.
Methods:
This study used repeat cross-sectional data from three waves of the International Cannabis Policy Study web-based survey. Data were collected from respondents aged 16-65 prior to cannabis legalisation in 2018 (n = 8704), and post-legalisation in 2019 (n = 12,236) and 2020 (n = 12,815). Respondents' postal codes were linked to the INSPQ neighbourhood deprivation index. Multinomial regression models examined differences in problematic use by socio-demographic and socio-economic factors and over time.
Results:
No evidence of a change in the proportion of those aged 16-65 in Canada whose cannabis use would be classified as 'high risk' was noted from before cannabis legalisation (2018 = 1.5%) to 12 or 24 months after legalisation (2019 = 1.5%, 2020 = 1.6%; F = 0.17, p = 0.96). Problematic use differed by socio-demographic factors. For example, consumers from the most materially deprived neighbourhoods were more likely to experience 'moderate' vs 'low risk' compared to those living outside deprived neighbourhoods (p < 0.01 for all). Results were mixed for race/ethnicity and comparisons for high risk were limited by small sample sizes for some groups. Differences across subgroups were consistent from 2018 to 2020.
Discussion and conclusions:
The risk of problematic cannabis use does not appear to have increased in the 2 years following cannabis legalisation in Canada. Disparities in problematic use persisted, with some racial minority and marginalised groups experiencing higher risk.
In 2018, Canada enacted the Cannabis Act, becoming only the second country (after Uruguay) to legalize the recreational consumption of cannabis. Although there is ongoing global disagreement on the risk-benefit profile of cannabis with increasing legalization in many parts of the world, the evidence of rising cannabis use prevalence postlegalization has been consistent. In contrast, postlegalization changes in various cannabis-related metrics have been inconsistent in Canada and other parts of the world. Furthermore, the implications of cannabis legalization on substance-related harms and benefits for people who use unregulated drugs, particularly opioids, remain unclear. Finally, although Canada did not legalize cannabis to address the opioid crisis, there is rising scientific and popular interest in the therapeutic potential of cannabis to mitigate opioid-related harms. This perspective highlights the implications of cannabis legalization on substance-related benefits and harms for people who use opioids, the current state of Canadian research, and suggestions for future directions.
Background
Investigation of cannabis use trends among emerging adults (EA, aged between 18 and 24 years) following 2018 Canadian Recreational Cannabis Legislation (RCL) is critical. EAs report the heaviest cannabis use in Canada and are particularly vulnerable to the onset of problematic substance use.
Objectives
To describe and compare post-RCL use of cannabis and other state-altering substances, as well as the prevalence of impaired driving, among EA postsecondary students in both rural and urban settings, studying on one of five campuses in either Manitoba, Ontario, or Quebec.
Methods
For this quantitative cross-sectional study, a self-report survey was administered to 1496 EA postsecondary students in the months following RCL (2018–2019). Multiple logistic regression analyses were conducted to explore the influence of provincial and urban/rural living contexts on recreational cannabis use, other state-altering substance use and impaired driving behaviours, adjusting for sociodemographic variables.
Results
Statistically significant differences were observed between cohorts in almost all measures. Quebec students were more likely to have consumed cannabis during their lifetime (AOR = 1.41, 95% CI [1.05, 1.90]) than all other cohorts. Rural cohorts all had greater odds of reporting consumption of cannabis during the previous year compared to urban cohorts (AOR = 1.32, 95% CI [1.04, 1.67]). However, the relation between cannabis use in the last month and operating a motor vehicle after using cannabis (lifetime and past month) and living context differed between subjects in Quebec and those in the two other provinces. Quebec’s students having lived mostly in urban contexts had greater odds of using cannabis in the past month and operating a motor vehicle after using cannabis (lifetime and past month) than those in rural contexts; the opposite was observed in Manitoba and Ontario. Differing interprovincial prohibitive/permissive legislation and licit cannabis infrastructure appeared to have little impact on post-RCL substance use.
Conclusions
In Manitoba and in Ontario, rural/urban living context seems to better predict substance use and related road-safety practices, suggesting these trends supersede permissive/prohibitive provincial legislation and licit cannabis-related infrastructures. Further investigation into sociodemographic factors influencing state-altering substance use and impaired driving, and maintaining tailored cannabis misuse prevention campaigns, is warranted on Canadian campuses.
Introduction:
Although there is momentum towards legalising adult recreational cannabis use worldwide, the extent of youth cannabis-related harm associated with legalisation is still uncertain. The current study aimed to assess whether the initial implementation of Canada's cannabis legalisation (via the Cannabis Act) on 17 October 2018 might be associated with youth harm, as assessed by emergency department visits for cannabis-related disorders/poisoning.
Methods:
We used Ontario and Alberta, Canada emergency department data from 1 April 2015 to 31 December 2019. We identified all cannabis-related disorders/poisoning (ICD-10 CA: F12.X, T40.7) emergency department visits of youth (n = 13,615), defined as patients younger than the minimum legal cannabis sales age (18 years, Alberta; 19 years, Ontario). Seasonal Autoregressive Integrated Moving Average (SARIMA) models were employed to assess the impact of legalisation on weekly counts of cannabis-related harms.
Results:
The final SARIMA intervention (step) parameter indicated a post-legalisation increase of 14.7 (95% confidence interval [CI] 5.0; 24.3, p < 0.01) weekly youth cannabis-related disorder/poisoning presentations to Ontario/Alberta emergency department settings, equivalent to an increase of 20.0% (95% CI 6.2%; 33.9%). There was no evidence of associations between cannabis legalisation and comparison series of youth alcohol, opioid or appendicitis emergency department episodes.
Discussion/conclusion:
Our findings require replication and extension but are consistent with the possibility that the implementation of the Cannabis Act was associated with an increase in youth cannabis-related presentations to Ontario/Alberta emergency departments.
Canada legalized non-medical cannabis use and supply for adults in 2018. We examined developments and changes associated with the legalization policy reform on key indicators for public health, namely cannabis (including frequent/problematic) use prevalence, cannabis-related hospitalizations, cannabis-impaired driving, and cannabis sourcing. We identified peer-reviewed and “grey” study data that featured population-level or other quasi-representative samples and comparable outcome data for pre- and post-legalization periods, including possible trends of changes over time. Cannabis use has increased in select population groups, with use modes shifting away from smoking. Evidence on cannabis-related hospitalizations (e.g., for mental health) is mixed. The prevalence of cannabis-impaired driving appears to be generally steady but THC exposure among crash-involved drivers may have increased. Increasing proportions of users obtain cannabis products from legal sources but some—especially regular—users continue to use illicit sources. Overall, data suggest a mixed and inconclusive picture on cannabis legalization’s impacts on essential public health indicators, including select extensions in trends from pre-legalization.
Issue:
On 17 October 2018, Canada legalised non-medical cannabis. Critically, the cannabis market in Canada has changed considerably since legalisation. In this scoping review, we identified available evidence on changes in cannabis-related health harms following legalisation and contextualised findings based on legal market indicators.
Approach:
Electronic searches were conducted to identify studies that compared changes in cannabis-related health harms pre- and post-legalisation. We contextualised each study by the mean per capita legal cannabis stores and sales during the study period and compared study means to per capita stores and sales on October 2021-3 years following legalisation.
Implications and conclusions:
Some measures of cannabis harms have increased since legalisation but studies to date have captured periods of relatively low market maturity. Longer-term monitoring of health harms as the market continues to expand is indicated.
Cannabis legalization for non-medical purposes (subsequently referred to as “cannabis legalization” or “legalization”) took place in Canada in October 2018. One of the federal government's stated goals with cannabis legalization was to protect Canadian youth from cannabis-related harms. The main objective of this narrative review is to describe the impact of cannabis legalization on Canadian youth. To that end, we discuss the regulation of the Canadian cannabis market, outline changes in the epidemiology and parameters of cannabis use (modes of use, potency of cannabis) among youth, and discuss prevention and education initiatives related to cannabis. The Canadian model differs from other jurisdictions that legalized recreational cannabis use, especially with regard to a higher degree of government regulation of the cannabis market. Another difference is the development and endorsement of lower-risk cannabis use guidelines to educate the public and health professionals. The results available for this review cover only 3 years post-legalization. Cannabis legalization in Canada brought an apparent increase in use among Canadian older than 25. However, results for youth are mixed, with the majority of studies showing no pronounced increase. Notably, the trend of a decrease in adolescents' cannabis use seen pre-legalization may have reversed. Emerging evidence also suggests that cannabis-related hospitalizations and emergency department visits among Canadian youth may have increased due to cannabis legalization. Data about changes in the age of initiation, the influence of legalization on sex and gender, and race/ethnicity are limited, with evidence suggesting that the age of initiation slightly increased. So far, there is limited data about the impact of cannabis legalization on Canadian youth. Further long-term monitoring and research to assess the effects of cannabis legalization on Canadian youth.
Impaired driving has been a considerable social problem in the U.S. for decades, but efforts to reduce it have stalled after the initial reductions in the 1980’s. As a result, legislators continue to develop more polices aimed at deterring impaired driving. Although alcohol has historically been the focus of these efforts, recently there has been increased concern about marijuana impaired driving policies as well. However, alcohol and marijuana impaired driving differ in many ways. This paper explores the costs and benefits of new zero-tolerance policies such as the reduction of the per-se Blood Alcohol Concentration (BAC) level from .08 to .05 for alcohol and the establishment of similar per-se limits for marijuana. These policies are not based on actual impairment and reflect a net widening effect that will criminalize unimpaired drivers, divert criminal justice resources away from the most problematic impaired drivers, and will have little impact on impaired driving crashes. As such, they have the potential to do more harm than good.
Marijuana use impairs driving,¹ but researchers have not yet conclusively determined if a state’s legalizing recreational marijuana is associated with traffic fatality rates. Two early studies reported no significant change in roadway deaths following legalization in Colorado and Washington,²,3 whereas a study including Oregon reported a temporary increase.⁴ A more recent study, including 2017 data, found a statistically significant increase in fatal crashes only after commercial stores opened, suggesting that the effect of legalization may take more time to observe.
Objectives
Non-medical cannabis recently became legal for adults in Canada. Legalization provides opportunity to investigate the public health effects of national cannabis legalization on presentations to emergency departments (EDs). Our study aimed to explore association between cannabis-related ED presentations, poison control and telemedicine calls, and cannabis legalization.
Methods
Data were collected from the National Ambulatory Care Reporting System from October 1, 2013, to July 31, 2019, for 14 urban Alberta EDs, from Alberta poison control, and from HealthLink, a public telehealth service covering all of Alberta. Visitation data were obtained to compare pre- and post-legalization periods. An interrupted time-series analysis accounting for existing trends was completed, in addition to the incidence rate ratio (IRR) and relative risk calculation (to evaluate changes in co-diagnoses).
Results
Although only 3 of every 1,000 ED visits within the time period were attributed to cannabis, the number of cannabis-related ED presentations increased post-legalization by 3.1 (range -11.5 to 12.6) visits per ED per month (IRR 1.45, 95% confidence interval [CI]; 1.39, 1.51; absolute level change: 43.5 visits per month, 95% CI; 26.5, 60.4). Cannabis-related calls to poison control also increased (IRR 1.87, 95% CI; 1.55, 2.37; absolute level change: 4.0 calls per month, 95% CI; 0.1, 7.9). Lastly, we observed increases in cannabis-related hyperemesis, unintentional ingestion, and individuals leaving the ED pre-treatment. We also observed a decrease in co-ingestant use.
Conclusion
Overall, Canadian cannabis legalization was associated with small increases in urban Alberta cannabis-related ED visits and calls to a poison control centre.
Acute cannabis use results in inattention, delayed information processing, impaired coordination, and slowed reaction time. Driving simulator studies and epidemiologic analyses suggest that cannabis use increases motor vehicle crash risk. How much concern should we have regarding cannabis associated motor vehicle collision risks among younger drivers? This article summarizes why young, inexperienced drivers may be at a particularly high risk of crashing after using cannabis. We describe the epidemiology of cannabis use among younger drivers, why combining cannabis with alcohol causes significant impairment and why cannabis edibles may pose a heightened risk to traffic safety. We provide recommendations for clinicians counselling younger drivers about cannabis use and driving.
Reducing impaired driving requires a systematic, consistent, and multifaceted approach. There is strong evidence on the effectiveness of both direct and indirect measures. The strategy that has the most immediate and largest impact has been highly publicized, visible, and frequent impaired-driving enforcement, especially deploying sobriety checkpoints or random breath testing. Lowering legal blood alcohol concentration (BAC) limits for driving to 0.05 g/dL or lower has also had a world-wide impact. Raising the legal drinking age has been successful in the US and other countries in reducing young impaired-driver fatal crashes. Graduated drivers' licensing for youth has also been effective by restricting conditions under which youth can drive. Sanctions that reduce impaired-driving recidivism include special driving-under-the-influence (DUI)/driving-while-intoxicated (DWI) courts, mandatory alcohol ignition interlocks, and consistent alcohol-monitoring programs. Opportunities for further progress include better enforcement of the drinking age and refusing to serve obviously intoxicated patrons. Technology for detecting alcohol impairment and autonomous vehicles will also play an important role in future efforts to eliminate impaired driving.
Globally, every day, ∼2,300 children and adolescents succumb to unintentional injuries sustained from motor vehicle collisions, drowning, poisoning, falls, burns, and violence. The rate of deaths due to motor vehicle injuries in adolescents is 10.2 per 100,000 adolescents. We systematically reviewed published evidence to identify interventions to prevent unintentional injuries among adolescents aged 11-19 years. We defined unintentional injuries as a subset of injuries for which there was no evidence of predetermined intent, and the definition included motor vehicle injuries, suffocation, drowning, poisoning, burns, falls, and sports and recreation. Thirty-five studies met study eligibility criteria. The included studies focused on interventions to prevent motor vehicle injuries and sports-related injuries. Results suggest that possession of a graduated driver license (GDL) significantly reduced road accidents by 19% (relative risk [RR]: .81; 95% confidence interval [CI]: .75-.88; n = 5). There was no impact of GDL programs on incidence of injuries (RR: .78; 95% CI: .57-1.06; n = 2), helmet use (RR: 1.0; 95% CI: .98-1.02; n = 3), and seat belt use (RR: .99; 95% CI: .97-1.0; n = 3). Sports-related injury prevention interventions led to reductions in the incidence of injuries (RR: .66; 95% CI: .53-.82; n = 15), incidence of injury per hour of exposure (RR: .63; 95% CI: .47-.86; n = 5), and injuries per number of exposures (RR: .79; 95% CI: .70-.88; n = 4). Subgroup analysis according to the type of interventions suggests that training ± education and the use of safety equipment had significant impacts on reducing the incidence of injuries. We did not find any study focusing on interventions to prevent suffocation, drowning, poisoning, burns, and falls in the adolescent age group. The existing evidence is mostly from high-income countries, limiting the generalizability of these findings for low- and middle-income countries. Studies evaluating these interventions need to be replicated in a low- and middle-income country-context to evaluate effectiveness with standardized outcome measures.
Automatic forecasts of large numbers of univariate time series are often needed in business and other contexts. We describe two automatic forecasting algorithms that have been implemented in the forecast package for R. The first is based on innovations state space models that underly exponential smoothing methods. The second is a step-wise algorithm for forecasting with ARIMA models. The algorithms are applicable to both seasonal and non-seasonal data, and are compared and illustrated using four real time series. We also briey describe some of the other functionality available in the forecast package.
Estimating the required sample size and statistical power for a study is an integral part of study design. For standard designs, power equations provide an efficient solution to the problem, but they are unavailable for many complex study designs that arise in practice. For such complex study designs, computer simulation is a useful alternative for estimating study power. Although this approach is well known among statisticians, in our experience many epidemiologists and social scientists are unfamiliar with the technique. This article aims to address this knowledge gap.
We review an approach to estimate study power for individual- or cluster-randomized designs using computer simulation. This flexible approach arises naturally from the model used to derive conventional power equations, but extends those methods to accommodate arbitrarily complex designs. The method is universally applicable to a broad range of designs and outcomes, and we present the material in a way that is approachable for quantitative, applied researchers. We illustrate the method using two examples (one simple, one complex) based on sanitation and nutritional interventions to improve child growth.
We first show how simulation reproduces conventional power estimates for simple randomized designs over a broad range of sample scenarios to familiarize the reader with the approach. We then demonstrate how to extend the simulation approach to more complex designs. Finally, we discuss extensions to the examples in the article, and provide computer code to efficiently run the example simulations in both R and Stata.
Simulation methods offer a flexible option to estimate statistical power for standard and non-traditional study designs and parameters of interest. The approach we have described is universally applicable for evaluating study designs used in epidemiologic and social science research.
Importance
An important consequence of cannabis legalization is the potential increase in the number of cannabis-impaired drivers on roads, which may result in higher rates of traffic-related injuries and fatalities. To date, limited information about the effects of recreational cannabis laws (RCLs) on traffic fatalities is available.
Objective
To estimate the extent to which the implementation of RCLs is associated with traffic fatalities in Colorado and Washington State.
Design, Setting, and Participants
This ecological study used a synthetic control approach to examine the association between RCLs and changes in traffic fatalities in Colorado and Washington State in the post-RCL period (2014-2017). Traffic fatalities data were obtained from the Fatality Analysis Reporting System from January 1, 2005, to December 31, 2017. Data from Colorado and Washington State were compared with synthetic controls. Data were analyzed from January 1, 2005, to December 31, 2017.
Main Outcome(s) and Measures
The primary outcome was the rate of traffic fatalities. Sensitivity analyses were performed (1) excluding neighboring states, (2) excluding states without medical cannabis laws (MCLs), and (3) using the enactment date of RCLs to define pre-RCL and post-RCL periods instead of the effective date.
Results
Implementation of RCLs was associated with increases in traffic fatalities in Colorado but not in Washington State. The difference between Colorado and its synthetic control in the post-RCL period was 1.46 deaths per 1 billion vehicle miles traveled (VMT) per year (an estimated equivalent of 75 excess fatalities per year; probability = 0.047). The difference between Washington State and its synthetic control was 0.08 deaths per 1 billion VMT per year (probability = 0.674). Results were robust in most sensitivity analyses. The difference between Colorado and synthetic Colorado was 1.84 fatalities per 1 billion VMT per year (94 excess deaths per year; probability = 0.055) after excluding neighboring states and 2.16 fatalities per 1 billion VMT per year (111 excess deaths per year; probability = 0.063) after excluding states without MCLs. The effect was smaller when using the enactment date (24 excess deaths per year; probability = 0.116).
Conclusions and Relevance
This study found evidence of an increase in traffic fatalities after the implementation of RCLs in Colorado but not in Washington State. Differences in how RCLs were implemented (eg, density of recreational cannabis stores), out-of-state cannabis tourism, and local factors may explain the different results. These findings highlight the importance of RCLs as a factor that may increase traffic fatalities and call for the identification of policies and enforcement strategies that can help prevent unintended consequences of cannabis legalization.
The sale of cannabis for adult recreational use has been made legal in nine US states since 2012, and nationally in Uruguay in 2013 and Canada in 2018. We review US research on the effects of legalization on cannabis use among adults and adolescents and on cannabis‐related harms; the impact of legalizing adult recreational use on cannabis price, availability, potency and use; and regulatory policies that may increase or limit adverse effects of legalization. The legalization of recreational cannabis use in the US has substantially reduced the price of cannabis, increased its potency, and made cannabis more available to adult users. It appears to have increased the frequency of cannabis use among adults, but not so far among youth. It has also increased emergency department attendances and hospitalizations for some cannabis‐related harms. The relatively modest effects on cannabis use to date probably reflect restrictions on the number and locations of retail cannabis outlets and the constraints on commercialization under a continued federal prohibition of cannabis. Future evaluations of legalization should monitor: cannabis sales volumes, prices and content of tetrahydrocannabinol; prevalence and frequency of cannabis use among adolescents and adults in household and high school surveys; car crash fatalities and injuries involving drivers who are cannabis‐impaired; emergency department presentations related to cannabis; the demand for treatment of cannabis use disorders; and the prevalence of regular cannabis use among vulnerable young people in mental health services, schools and the criminal justice system. Governments that propose to legalize and regulate cannabis use need to fund research to monitor the impacts of these policy changes on public health, and take advantage of this research to develop ways of regulating cannabis use that minimize adverse effects on public health.
Introduction
Motor vehicle crashes are a leading cause of injury death in the U.S. Restrictive alcohol policies protect against crashes involving alcohol above the legal blood alcohol concentration of 0.08%. Characteristics of motor vehicle crash fatalities involving blood alcohol concentrations below the limit and their relationships to alcohol control policies have not been well characterized.
Methods
Motor vehicle crash fatality data and crash and decedent characteristics from 2000 to 2015 came from the Fatality Analysis Reporting System and were analyzed in 2018–2019. Alcohol Policy Scale scores characterized alcohol policy environments by state-year. Generalized estimating equation alternating logistic regression models assessed these scores and the odds that a fatality involved alcohol below the legal threshold.
Results
Of 612,030 motor vehicle crash fatalities, 223,471 (37%) died in alcohol-involved crashes, of which 33,965 (15% of alcohol-involved fatalities or 6% of all fatalities) had a blood alcohol concentration <0.08%. A 10 percentage point increase in Alcohol Policy Scale score, approximating the interquartile range among states, was associated with reduced odds of fatalities involving alcohol <0.08% vs 0.00% (AOR=0.91, 95% CI=0.89, 0.93). These findings held across multiple subgroup analyses by decedent and crash characteristics. Similar results were found for odds of alcohol involvement <0.05% vs 0.00% (AOR=0.90, 95% CI=0.88, 0.93), and ≥0.05% but <0.08% vs <0.05% (AOR=0.93, 95% CI=0.89, 0.96).
Conclusions
The number of lower blood alcohol concentration fatalities is substantial. States with more restrictive alcohol policies tend to have reduced odds of lower blood alcohol concentration motor vehicle crashes than states with weaker policies.
Background:
The Canadian government legalized non-medical cannabis use by adults in October 2018 in order to minimize associated harms and re-direct profits from criminals.
Data and methods:
Seven quarters of (NCS) data were combined into two groups: pre- and post-legalization periods - to examine changes in: cannabis use (overall, daily or almost daily (DAD)), source of product, driving after consumption and riding in a vehicle with a driver who had consumed.
Results:
By 2019, overall cannabis use had increased (16.8% vs. 14.9%), particularly among: males, adults aged 25 and older, and in Newfoundland and Labrador, Nova Scotia, New Brunswick, and Alberta. DAD use, at 6.0%, remained stable, as did the prevalence of driving within 2 hours of consumption (13.2%). Riding in a vehicle with a driver who had used declined, overall (from 5.3% to 4.2%) and among: females, persons aged 25 and older, and in Newfoundland and Labrador, Ontario and Alberta. Where Canadians reported obtaining their cannabis also changed, with increasing percentages reporting getting some or all of their cannabis from legal sources, and fewer using illegal sources or relying on friends/family. Some provinces experienced more change than others.
Discussion:
While too soon to observe the longer-term impacts associated with the Cannabis Act, early indications based on data collected in the months surrounding enactment suggests some cautions and also some assurances. Ongoing monitoring will be essential particularly given the 2.0 Act modifications and the ever-changing provincial retail and regulatory landscapes.
Background and aims:
While cannabis use has been found to impair motor vehicle driving, the association between cannabis legalisation and motor vehicle fatalities is unclear. In Uruguay in December 2013, cannabis for recreational purposes was legalized. This study assessed the association between implementation of this law and changes in traffic fatality rates.
Design:
Interrupted time series analysis of traffic fatality rates of light motor vehicle drivers and motorcyclists in urban and rural settings. Changes are reported as step and trend effects against modelled trends in the absence of legalisation.
Setting:
Uruguay, Montevideo and four rural provinces (Colonia, Florida, Río Negro and San José) from January 1st , 2012 to December 31st , 2017.
Cases and measurement:
Weekly traffic fatalities of light motor vehicle drivers and motorcyclists per type of vehicle. Data were gathered from the National Road Safety Agency of Uruguay and the Ministry of Transport and Public Works respectively.
Results:
Cannabis legalisation was associated with a 52.4% immediate increase (95% CI: 11.6, 93.3, p = 0.012) in the light motor vehicle driver's fatality rate. However, no significant change in the motorcyclists' fatality rate was observed. In Montevideo the legislation was associated with an absolute increase in its light motor vehicle driver's fatality rate by 0.06 (95% CI: 0.01, 0.11, P = 0.025), but no significant associations were observed in rural settings.
Conclusions:
In Uruguay, the 2013 legislation legalizing recreational cannabis consumption may have been associated with an increase in fatal motor vehicle crashes, particularly in light motor-vehicle drivers and urban settings.
Colorado and Washington legalized recreational marijuana in 2012, but the effects of legalization on motor vehicle crashes remains unknown. Using Fatality Analysis Reporting System data, we performed difference-in-differences (DD) analyses comparing changes in fatal crash rates in Washington, Colorado and nine control states with stable anti-marijuana laws or medical marijuana laws over the five years before and after recreational marijuana legalization. In separate analyses, we evaluated fatal crash rates before and after commercial marijuana dispensaries began operating in 2014. In the five years after legalization, fatal crash rates increased more in Colorado and Washington than would be expected had they continued to parallel crash rates in the control states (+1.2 crashes/billion vehicle miles traveled, CI: -0.6 to 2.1, p = 0.087), but not significantly so. The effect was more pronounced and statistically significant after the opening of commercial dispensaries (+1.8 crashes/billion vehicle miles traveled, CI: +0.4 to +3.7, p = 0.020). These data provide evidence of the need for policy strategies to mitigate increasing crash risks as more states legalize recreational marijuana.
Importance
Civil liberty advocates typically support legalization of cannabis, which targets adult use, rather than decriminalization, which can affect both adults and youths. However, it is unknown how arrests of youths for cannabis possession change when adult use of cannabis is legalized.
Objective
To model changes in arrest rates of adults and youths after decriminalization and legalization of cannabis.
Design, Setting, and Participants
This quasi-experimental study used the publicly available Uniform Crime Reporting Program Data: Arrests by Age, Sex, and Race administrative data set to examine arrest rates in 38 states from January 1, 2000, to December 31, 2016. Adult (age, ≥18 years) and youth (age, <18 years) arrests for possession of cannabis were examined. States were excluded if they did not report complete arrest data or if a policy was implemented that reduced penalties for possession of cannabis but fell short of decriminalization. Fixed-effects regression was used in an extended difference-in-differences framework. The analyses in their final form were conducted between January 17 and February 28, 2019.
Exposure
Living in a state with a cannabis decriminalization policy (ie, making the penalty for cannabis possession similar to the small fine for a traffic violation) or legalization policy (ie, creating a legal supply of cannabis along with the removal of penalties for possession of a small amount of cannabis for recreational use).
Main Outcome and Measures
State cannabis possession arrest rate per 100 000 population.
Results
Data from 38 states were examined, including 4 states with cannabis legalization policies and 7 states with cannabis decriminalization policies. The adult arrest rate decreased by 131.28 (95% CI, 106.23-154.21) per 100 000 population after the implementation of decriminalization and 168.50 (95% CI, 158.64-229.65) per 100 000 population after the implementation of legalization. The arrest rate for youths decreased by 60 (95% CI, 42-75) per 100 000 population after decriminalization but did not significantly change after legalization in a state (7 per 100 000 population; 95% CI, −15 to 30).
Conclusions and Relevance
Legalization, as implemented through 2016, did not appear to reduce arrests for cannabis possession among youths, despite having benefited adults. The study’s findings suggest that decriminalization reduces youth arrests in most cases, but these findings also suggest that any benefit for youths could be lost when adult use has also been legalized. To address this problem, it appears that state decriminalization policies should take the additional step to explicitly describe when youths can be arrested for possession of small amounts of cannabis.
Background and aims
A growing body of evidence suggests that cannabis impairs driving ability. We used mortality data to investigate whether the commercial sale of cannabis for recreational use affected traffic fatality rates both in states that legalized it and in neighbouring jurisdictions.
Design
Interrupted time–series of traffic fatality rates adjusted for seasonality and autocorrelation. Changes are reported as step and trend effects against a comparator of states that had not implemented medicinal or recreational cannabis during the study period (2009–16). Sensitivity analyses added a 6‐month ‘phase‐in’ to account for lags in production. Meta‐analyses were used to derive pooled results.
Setting
Three states that legalized recreational cannabis sales [Colorado (January 2014), Washington State (June 2014) and Oregon (October 2015] and nine neighbouring jurisdictions [Kansas, Nebraska, New Mexico, Oklahoma and Utah (Colorado neighbours); British Columbia and Oregon (Washington neighbours); and California and Nevada (Oregon neighbours)].
Measurements
Monthly traffic fatalities rates per million residents using mortality data from CDC WONDER and RoadSafetyBC and census data.
Findings
There was a pooled step increase of 1.08 traffic fatalities per million residents followed by a trend reduction of −0.06 per month (both P < 0.001), although with significant heterogeneity between sites (step: I² = 73.7%, P < 0.001; trend: I² = 68.4%; P = 0.001). Effects were similar in both legalizing (step: 0.90, P < 0.001; trend: −0.05, P = 0.007) and neighbouring sites (step: 1.15, P = 0.005; trend: −0.06, P = 0.001). The 6‐month phase‐in produced similar if larger effects (step: 1.36, P = 0.006; trend: −0.07, P < 0.001).
Conclusions
The combination of step increases and trend reductions suggests that in the year following implementation of recreational cannabis sales, traffic fatalities temporarily increased by an average of one additional traffic fatality per million residents in both legalizing US states of Colorado, Washington and Oregon and in their neighbouring jurisdictions.
Over the last few years, marijuana has become legally available for recreational use to roughly a quarter of Americans. Policy makers have long expressed concerns about the substantial external costs of alcohol, and similar costs could come with the liberalization of marijuana policy. Indeed, the fraction of fatal accidents in which at least one driver tested positive for tetrahydrocannabinol has increased nationwide by an average of 10% from 2013 to 2016. For Colorado and Washington, both of which legalized marijuana in 2014, these increases were 92% and 28%, respectively. However, identifying a causal effect is difficult due to the presence of significant confounding factors. We test for a causal effect of marijuana legalization on traffic fatalities in Colorado and Washington with a synthetic control approach using records on fatal traffic accidents from 2000 to 2016. We find the synthetic control groups saw similar changes in marijuana‐related, alcohol‐related, and overall traffic fatality rates despite not legalizing recreational marijuana. (JEL K42, I12, I18)
Importance
Motor vehicle crashes are a leading cause of mortality. However, the association between the restrictiveness of the alcohol policy environment (ie, based on multiple existing policies) and alcohol-related crash fatalities has not been characterized previously to date.
Objective
To examine the association between the restrictiveness of state alcohol policy environments and the likelihood of alcohol involvement among those dying in motor vehicle crashes in the United States.
Design, Setting, and Participants
This investigation was a repeated cross-sectional study in which state alcohol policies (operationalized by the Alcohol Policy Scale [APS]) from 1999 to 2014 were related to motor vehicle crash fatalities from 2000 to 2015 using data from the Fatality Analysis Reporting System (1-year lag). Alternating logistic regression models and generalized estimating equations were used to account for clustering of multiple deaths within a crash and of multiple crashes occurring within states. The study also examined independent associations of mutually exclusive subgroups of policies, including consumption-oriented policies vs driving-oriented policies. The study setting was the 50 US states. Participants were 505 614 decedents aged at least 21 years from motor vehicle crashes from 2000 to 2015.
Main Outcomes and Measures
Odds that a crash fatality was alcohol related (fatality stemmed from a crash in which ≥1 driver had a blood alcohol concentration [BAC] ≥0.08%).
Results
From 2000 to 2015, there were 505 614 adult motor vehicle crash fatalities in the United States, of which 178 795 (35.4%) were alcohol related. Each 10–percentage point increase in the APS score (corresponding to more restrictive state policies) was associated with reduced individual-level odds of alcohol involvement in a crash fatality (adjusted odds ratio [aOR], 0.90; 95% CI, 0.89-0.91); results were consistent among most demographic and crash-type strata. More restrictive policies also had protective associations with alcohol involvement among crash fatalities associated with BACs from greater than 0.00% to less than 0.08%. After accounting for driving-oriented policies, consumption-oriented policies were independently protective for alcohol-related crash fatalities (aOR, 0.97; 95% CI, 0.96-0.98 based on a 10–percentage point increased APS score).
Conclusions and Relevance
Strengthening alcohol policies, including those that do not specifically target impaired driving, could reduce alcohol-related crash fatalities. Policies may also protect against crash fatalities involving BAC levels below the current legal limit for driving in the United States.
Objectives:
To evaluate motor vehicle crash fatality rates in the first 2 states with recreational marijuana legalization and compare them with motor vehicle crash fatality rates in similar states without recreational marijuana legalization.
Methods:
We used the US Fatality Analysis Reporting System to determine the annual numbers of motor vehicle crash fatalities between 2009 and 2015 in Washington, Colorado, and 8 control states. We compared year-over-year changes in motor vehicle crash fatality rates (per billion vehicle miles traveled) before and after recreational marijuana legalization with a difference-in-differences approach that controlled for underlying time trends and state-specific population, economic, and traffic characteristics.
Results:
Pre-recreational marijuana legalization annual changes in motor vehicle crash fatality rates for Washington and Colorado were similar to those for the control states. Post-recreational marijuana legalization changes in motor vehicle crash fatality rates for Washington and Colorado also did not significantly differ from those for the control states (adjusted difference-in-differences coefficient = +0.2 fatalities/billion vehicle miles traveled; 95% confidence interval = -0.4, +0.9).
Conclusions:
Three years after recreational marijuana legalization, changes in motor vehicle crash fatality rates for Washington and Colorado were not statistically different from those in similar states without recreational marijuana legalization. Future studies over a longer time remain warranted. (Am J Public Health. Published online ahead of print June 22, 2017: e1-e3. doi:10.2105/AJPH.2017.303848).
State-level marijuana liberalization policies have been evolving for the past five decades, and yet the overall scientific evidence of the impact of these policies is widely believed to be inconclusive. In this review we summarize some of the key limitations of the studies evaluating the effects of decriminalization and medical marijuana laws on marijuana use, highlighting their inconsistencies in terms of the heterogeneity of policies, the timing of the evaluations, and the measures of use being considered. We suggest that the heterogeneity in the responsiveness of different populations to particular laws is important for interpreting the mixed findings from the literature, and we highlight the limitations of the existing literature in providing clear insights into the probable effects of marijuana legalization.
Cannabis is the most common illicit drug used worldwide and it is used frequently by Canadian teenagers. Cannabis use during adolescence can cause functional and structural changes to the developing brain, leading to damage. Marijuana use in this age group is strongly linked to: cannabis dependence and other substance use disorders; the initiation and maintenance of tobacco smoking; an increased presence of mental illness, including depression, anxiety and psychosis; impaired neurological development and cognitive decline; and diminished school performance and lifetime achievement. Rates of acute medical care and hospitalization for younger children who have ingested cannabis unintentionally are increasing. Ongoing debate concerning cannabis regulation in Canada makes paying close attention to the evidence for its health effects and ensuring that appropriate safeguards are in place, vital public health priorities.
Background and aims: Since 2012 four US states have legalized the retail sale of cannabis for recreational use by adults, and more are likely to follow. This report aimed to (1) briefly describe the regulatory regimes so far implemented; (2) outline their plausible effects on cannabis use and cannabis-related harm; and (3) suggest what research is needed to evaluate the public health impact of these policy changes. Method: We reviewed the drug policy literature to identify: (1) plausible effects of legalizing adult recreational use on cannabis price and availability; (2) factors that may increase or limit these effects; (3) pointers from studies of the effects of legalizing medical cannabis use; and (4) indicators of cannabis use and cannabis-related harm that can be monitored to assess the effects of these policy changes. Results: Legalization of recreational use will probably increase use in the long term, but the magnitude and timing of any increase is uncertain. It will be critical to monitor: cannabis use in household and high school surveys; cannabis sales; the number of cannabis plants legally produced; and the tetrahydrocannabinol (THC) content of cannabis. Indicators of cannabis-related harms that should be monitored include: car crash fatalities and injuries; emergency department presentations; presentations to addiction treatment services; and the prevalence of regular cannabis use among young people in mental health services and the criminal justice system. Conclusions: Plausible effects of legalizing recreational cannabis use in the United States include substantially reducing the price of cannabis and increasing heavy use and some types of cannabis-related harm among existing users. In the longer term it may also increase the number of new users.
Once associated with ‘deviant’ subcultures, the use of cannabis is now common across Canadian society. This has led some to argue that cannabis use is becoming normalized in Canada with important implications for drug policy, law enforcement and public health. This article takes up these issues, reporting the results of a qualitative study involving 165, socially integrated, adult cannabis users in four Canadian cities (Vancouver, Montreal, Toronto and Halifax). The aims of this study were twofold; first, we sought to contribute to recent efforts to extend the analysis of normalization and its associated features from adolescent and young adult populations to older adults, with a particular focus on cannabis. Second, we wished to respond to recent calls for greater analysis of both the social and structural determinants of normalization, as well as its contingent, ‘micro-level’ features. Our examination of these diverse dimensions revealed significant changes in the meaning and status of cannabis use in Canada. Although some social and personal stigmas remain, our research suggests they are largely confined to the immoderate, ‘irresponsible’ use of cannabis, while more ‘controlled’ use among adults appears all but de-stigmatized. This process has involved changes in the ways risks associated with cannabis use are characterized and managed; shifts in the ways adult cannabis users seek to moderate their use; as well as broader social and cultural shifts in the meanings associated with cannabis in Canada. We conclude with a discussion of the potential impacts of these developments for drug policy debates in Canada and elsewhere.
This article discusses the effect of interventions on a given response variable in the presence of dependent noise structure. Difference equation models are employed to represent the possible dynamic characteristics of both the interventions and the noise. Some properties of the maximum likelihood estimators of parameters measuring level changes are discussed. Two applications, one dealing with the photochemical smog data in Los Angeles and the other with changes in the consumer price index, are presented.
In an earlier paper (Durbin & Watson, 1950) the authors investigated the problem of testing the error terms of a regression model for serial correlation. Test criteria were put forward, their moments calculated, and bounds to their distribution functions were obtained. In the present paper these bounds are tabulated and their use in practice is described. For cases in which the bounds do not settle the question of significance an approximate method is suggested. Expressions are given for the mean and variance of a test statistic for one- and two-way classifications and polynomial trends, leading to approximate tests for these cases. The procedures described should be capable of application by the practical worker without reference to the earlier paper (hereinafter referred to as Part I).
Unlabelled:
Unintentional injury from motor-vehicle crashes is the number one cause of death among teenagers in the United States. Increasingly, jurisdictions have adopted three-stage graduated driver licensing (GDL) systems for young novice drivers. Since a previous review of U.S. GDL evaluation results, many more U.S. states and Canadian provinces have implemented GDL and/or had enough time pass that additional evaluation results are now available. Twenty-one studies of GDL within 14 individual jurisdictions, and six studies of GDL in the U.S. nationwide, were collected, reviewed, and summarized. Positive results (usually crash reductions) of varying degrees were reported from nearly all the studies. Given differences in approaches, study goals, methods, and analyses, the results are surprisingly consistent. Overall, GDL programs have reduced the youngest drivers' crash risk by roughly 20 to 40%. Research on teen driving and comprehensive GDL enhancements could further reduce teen drivers' motor-vehicle crashes, injuries, and fatalities.
Impact on industry:
Policy-makers, as well as the motor vehicle, insurance, and other industries have been involved in teen driving safety and could enhance and coordinate their roles.
The history of the development of statistical hypothesis testing in time series analysis is reviewed briefly and it is pointed out that the hypothesis testing procedure is not adequately defined as the procedure for statistical model identification. The classical maximum likelihood estimation procedure is reviewed and a new estimate minimum information theoretical criterion (AIC) estimate (MAICE) which is designed for the purpose of statistical identification is introduced. When there are several competing models the MAICE is defined by the model and the maximum likelihood estimates of the parameters which give the minimum of AIC defined by AIC = (-2)log-(maximum likelihood) + 2(number of independently adjusted parameters within the model). MAICE provides a versatile procedure for statistical model identification which is free from the ambiguities inherent in the application of conventional hypothesis testing procedure. The practical utility of MAICE in time series analysis is demonstrated with some numerical examples.
Canada’s chronic shortage of legal cannabis expected to drag out for years
- Armstrong