Operating a motor vehicle after marijuana use: Perspectives from people who use high-potency marijuana

Systematic Review and Meta-Analysis: Medical and Recreational Cannabis Legalization and Cannabis Use Among Youth in the United States

OBJECTIVE

Dramatic changes in state-level cannabis laws (CL) over the past 25 years have shifted societal beliefs throughout the United States, with unknown implications for youth. In the present study, we conducted an updated systematic review and meta-analysis examining estimated effects of medical cannabis legalization (MCL) and recreational cannabis legalization (RCL) on past-month cannabis use among US youth.

METHOD

A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, followed by a subsequent meta-analysis investigating the associations between state-level cannabis laws (ie, MCL vs non-MCL, and RCL vs non-RCL) and past-month cannabis use prevalence among US adolescents and young adults. Supplemental analyses examined age-group effects and design-related factors.

RESULTS

Our search identified 4,604 citations, 34 and 30 of which were included in qualitative and quantitative analyses, respectively. Meta-analysis of MCL studies identified no significant association between MCL and change in past-month youth cannabis use (odds ratio [OR] = 0.981, 95% CI = 0.960, 1.003). Meta-analysis of RCL studies showed significantly increased odds of past-month cannabis use (OR = 1.134, 95% CI = 1.116-1.153). Meta-analysis of more recent studies, however, showed a significantly increased odds of past-month cannabis use among both adolescents and young adults (OR = 1.089, 95% CI = 1.015,1.169, and OR = 1.221, 95% CI = 1.188,1.255, respectively).

CONCLUSION

Cannabis legalization has complex and heterogenous effects on youth use that may differ across law types. Our meta-analytic results showed modest positive effects of RCL on past-month cannabis use (more so in young adults than in adolescents) and minimal effects of MCL on these outcomes in US youth. Given the shift toward recreational legalization, additional focus on RCL effects is warranted.

Driving under the influence of cannabis: perceptions from Canadian youth

BACKGROUND

Cannabis legalization is intended to protect the public from potential harm by restricting access and promoting greater awareness of cannabis-related risks. Youth are at a greater risk for experiencing road-related harms due to their own or others' use of cannabis. This qualitative research explored youths' perceptions about cannabis and road safety.

METHODS

A qualitative study using focus groups (FG) was conducted with youth (age 13-18) and young adults (age 19-25) who resided in Newfoundland and Labrador. Using semi-structured interview questions, the facilitator asked participants to share their opinions about cannabis and road safety. All sessions were hosted virtually using Zoom with recruitment until saturation was met. All sessions were audio recorded, de-identified, and transcribed. Analysis utilized an inductive thematic approach informed by Braun and Clarke's (2006) method and inductive coding was facilitated using NVivo.

RESULTS

Six youth (n = 38) and five young adult (n = 53) FG were conducted. Five prominent themes emerged throughout discussions across both age groups including: a) normalization of driving under the influence of cannabis, b) knowledge and awareness, c) perceptions of risk, d) modes of transportation, and e) detection. Variation in perceptions appeared to be influenced by lack of awareness of the impact of cannabis on driving ability, residence in urban versus rural locations, type of vehicle driven (e.g., car vs. off-road vehicles), and gender.

CONCLUSION

The themes uncovered from this research will help inform future enhancement of cannabis policy to ensure the safety of all citizens. These findings will also support the inclusion of youth-focused education that will equip youth with informed decision-making strategies regarding road safety. Furthermore, these findings can be utilized to inform the refinement of cannabis driving policies to ensure the safety of all citizens on or off the road.

A systematic review of factors associated with illegal drug driving

Drug driving is a serious problem worldwide that can increase the risk of road crashes. This systematic review seeks to identify factors associated with drug driving (i.e., driving after consuming drugs other than alcohol) to highlight gaps in existing knowledge and inform the design of more effective countermeasures. A search of the literature was conducted for the period January 1, 2005 to July 31, 2021 using six different databases. The search protocol followed PRISMA guidelines and was registered in PROSPERO (#CRD42021234616). Studies that met inclusion criteria compared drug drivers with either non-drug drivers, alcohol-only drivers or drug drivers from an earlier time period, to identify factors specifically associated with drug driving, rather than common to all drivers. Two hundred and nineteen publications met the inclusion criteria and were included within the review. Based on the findings, a logic model was developed that presents the factors associated with drug driving. Various sociodemographic, psychosocial and legal factors emerged as the main factors associated with illegal drug driving. At the sociodemographic and psychological levels, drug drivers were more likely to be single, young males who often drive after using cannabis and who score high on sensation-seeking and impulsivity scales. The key social factor found to be associated with drug driving was peer acceptance/disapproval of the behaviour. At the legal level, the review suggested that the effectiveness of current enforcement approaches to drug driving vary among jurisdictions around the world due to differences in the level of perceived certainty of apprehension and the chances of punishment avoidance. Future research into the anticipated and actual rewards for drug driving is needed to inform the development of more effective countermeasures.

Lower-Risk Cannabis Use Guidelines (LRCUG) for reducing health harms from non-medical cannabis use: A comprehensive evidence and recommendations update

BACKGROUND

Cannabis use is common, especially among young people, and is associated with risks for various health harms. Some jurisdictions have recently moved to legalization/regulation pursuing public health goals. Evidence-based 'Lower Risk Cannabis Use Guidelines' (LRCUG) and recommendations were previously developed to reduce modifiable risk factors of cannabis-related adverse health outcomes; related evidence has evolved substantially since. We aimed to review new scientific evidence and to develop comprehensively up-to-date LRCUG, including their recommendations, on this evidence basis.

METHODS

Targeted searches for literature (since 2016) on main risk factors for cannabis-related adverse health outcomes modifiable by the user-individual were conducted. Topical areas were informed by previous LRCUG content and expanded upon current evidence. Searches preferentially focused on systematic reviews, supplemented by key individual studies. The review results were evidence-graded, topically organized and narratively summarized; recommendations were developed through an iterative scientific expert consensus development process.

RESULTS

A substantial body of modifiable risk factors for cannabis use-related health harms were identified with varying evidence quality. Twelve substantive recommendation clusters and three precautionary statements were developed. In general, current evidence suggests that individuals can substantially reduce their risk for adverse health outcomes if they delay the onset of cannabis use until after adolescence, avoid the use of high-potency (THC) cannabis products and high-frequency/-intensity of use, and refrain from smoking-routes for administration. While young people are particularly vulnerable to cannabis-related harms, other sub-groups (e.g., pregnant women, drivers, older adults, those with co-morbidities) are advised to exercise particular caution with use-related risks. Legal/regulated cannabis products should be used where possible.

CONCLUSIONS

Cannabis use can result in adverse health outcomes, mostly among sub-groups with higher-risk use. Reducing the risk factors identified can help to reduce health harms from use. The LRCUG offer one targeted intervention component within a comprehensive public health approach for cannabis use. They require effective audience-tailoring and dissemination, regular updating as new evidence become available, and should be evaluated for their impact.

Modeling the System of Beliefs That Affect Driving Under the Influence of Cannabis and Alcohol in Washington State

Washington state has observed increases in polydrug use in fatal crashes, primarily involving the combination of cannabis and alcohol. The purpose of this article is to explore the belief system associated with driving under the influence of cannabis and alcohol (DUICA) in Washington state using structural equation modeling (SEM). A convenience sample ( n = 737) of surveys collected from adults in Washington state was analyzed using SEM to reveal the latent structure of the belief system associated with DUICA. The results of this analysis indicated that the reported DUICA behavior (frequency) was predicted by intention and willingness. Willingness also predicted intention. Intention and willingness were predicted by positive attitudes toward DUICA, as well as normative perceptions that it was acceptable to important people and common behavior for most people. These components were themselves predicted by corresponding beliefs (behavioral beliefs, normative beliefs, and control beliefs). Finally, these beliefs were also influenced by the values that were most important to the respondents. Based on these results, it is reasonable to speculate that strategies to change these beliefs may also reduce DUICA behavior and associated fatal crashes.

Medical marijuana laws and driving under the influence of marijuana and alcohol

AIMS

Medical marijuana law (MML) enactment in the United States has been associated with increased cannabis use but lower traffic fatality rates. We assessed the possible association of MML and individual-level driving under the influence of cannabis (DUIC) and also under the influence of alcohol (DUIA).

DESIGN AND SETTING

Three cross-sectional U.S. adult surveys: The National Longitudinal Alcohol Epidemiologic Survey (NLAES; 1991-1992), the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC; 2001-2002), and the NESARC-III (2012-2013).

PARTICIPANTS

The total n was 118 497: 41 764, 41 184, and 35 549 from NLAES, NESARC, and NESARC-III, respectively.

MEASUREMENTS

Across the three surveys, similar questions in the Alcohol Use Disorder and Associated Disabilities Interview Schedule assessed DUIC and DUIA. Ever-MML states enacted MML between 1991-1992 and 2012-2013 (overall period). Early-MML states enacted MML between 1991-1992 and 2001-2002 (early period). Late-MML states enacted MML between 2001-2002 and 2012-2013 (late period). MML effects on change in DUIC and DUIA prevalence were estimated using a difference-in-differences specification to compare changes in MML and other states.

FINDINGS

From 1991-1992 to 2012-2013, DUIC prevalence nearly doubled (from 1.02% to 1.92%), increasing more in states that enacted MML than other states (difference-in-differences [DiD] = 0.59%; 95% CI = 0.06%-1.12%). Most change in DUIC prevalence occurred between 2001-2002 and 2012-2013. DUIC prevalence increased more in states that enacted MML 2001-2002 to 2012-2013 than in never-MML states (DiD = 0.77%; 95% CI = -0.05%-1.59%), and in two early-MML states, California (DiD = 0.82; 95% CI = 0.06-1.59) and Colorado (DiD = 1.32; 95% CI = 0.11-2.53). In contrast, DUIA prevalence appeared unrelated to MML enactment.

CONCLUSIONS

Medical marijuana law enactment in US states appears to have been associated with increased prevalence of driving under the influence of cannabis, but not alcohol.

Association of Recreational Cannabis Laws in Colorado and Washington State With Changes in Traffic Fatalities, 2005-2017

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.

Blunted highs: Pharmacodynamic and behavioral models of cannabis tolerance

Acute exposure to cannabis comes with neurocognitive impairment, leading to increased risk of human error and injury. Evidence however indicates that such acute effects are less prominent in chronic users, suggesting cannabis tolerance. Models of cannabis tolerance stress the importance of neurobiological or behavioral adaptations following repeated cannabis exposure. The pharmacodynamic model relates neuroadaptive changes in the brain to a blunted response to cannabis. Downregulation of CB1 receptors in chronic cannabis users has been associated with a normalization of dopaminergic output from the ventral tegmental area to the mesolimbic circuit, and a reduction of impairment during acute cannabis exposure. Such neuroadaptions are absent in occasional users, who show strong increments of dopamine and glutamate levels in the striatum, a loss of functional connectivity within the mesolimbic circuit and neurocognitive impairments when exposed to cannabis. Evidence for a behavioral model of cannabis tolerance that poses that users can have volitional control to overcome functional impairment during cannabis intoxication is relatively weak, and at best shows limited control over a limited number of behavioral functions. Cannabis tolerance is most likely to occur in users that consume high doses of cannabis continuously, at a high pace, for a prolonged period of time. Knowledge on frequency, dose and duration of cannabis use that is needed to achieve, maintain or lessen tolerance however is very limited, but will be of importance in the context of cannabis therapeutics and in legal settings when evaluating the impact of cannabis exposure on human function.

Marijuana Use and Potential Implications of Marijuana Legalization

Most states in the United States have legalized medical and/or recreational cannabis in response to public demand. Trends in states adopting such legislation demonstrate an increasing prevalence of cannabis use coincident to decreasing perceptions of risk of harm from cannabis products. When providing anticipatory guidance, pediatricians should be prepared to address childhood unintentional ingestion management and prevention, adolescent problem use, and cannabis as an alternative therapy for seizure disorders and other conditions.

Perceived safety of cannabis intoxication predicts frequency of driving while intoxicated

Driving under the influence of cannabis (DUIC) is a public health concern, and data are needed to develop screening and prevention tools. Measuring the level of intoxication that cannabis users perceive as safe for driving could help stratify DUIC risk. This study tested whether intoxication levels perceived as safe for driving predicted past-month DUIC frequency. Online survey data were collected in 2017 from a national sample of n = 3010 past-month cannabis users with lifetime DUIC (age 18+). Respondents indicated past-month DUIC frequency, typical cannabis intoxication level (1-10 scale), and cannabis intoxication level perceived as safe for driving (0-10 scale). Approximately 24%, 38%, 13%, and 24% of respondents engaged in DUIC on 0, 1-9, 10-19, and 20-30 days respectively in the past month. Among these four DUIC frequency groups, median typical intoxication varied little (5-6), but median intoxication perceived as safe for driving varied widely (3-8). Higher intoxication levels perceived as safe for driving corresponded to frequent DUIC (Spearman's rho: 0.46). For each unit increase in intoxication level perceived as safe for driving, the odds of past-month DUIC increased 18% to 68% (multinomial logistic regression odds ratio - MOR1-9 days: 1.18, 95% CI: 1.13-1.23; MOR10-19 days: 1.40, 95% CI: 1.30-1.50; MOR20-30 days: 1.68, 95% CI: 1.57-1.80). In this targeted sample of past-month cannabis users, DUIC frequency varied widely, but daily/near-daily DUIC was common (24%). Measuring intoxication levels perceived as safe for driving permits delineation of past-month DUIC frequency. This metric has potential as a component of public health prevention tools.

Cannabis use in older drivers in Colorado: The LongROAD Study

This study examined cannabis use and driving outcomes among older drivers in Colorado, which has legalized medical and recreational use. The associations of self-reported past-year cannabis use with diverse driving outcomes were assessed in 598 drivers aged 65-79 (51% female, 70% with postsecondary education), using regression analysis to adjust for health and sociodemographic characteristics. Two hundred forty four (40.8%) drivers reported ever using cannabis. Fifty-four drivers (9.0%) reported past-year use, ranging from more than once a day (13.0%) to less than once a month (50.0%). Of past-year users, 9.3% reported cannabis use within 1 h of driving in the past year. Past-year users were younger, less highly educated, lower income, and reported significantly worse mental, emotional, social and cognitive health status than drivers without past-year use. Past-year users were four times as likely to report having driven when they may have been over the legal blood-alcohol limit (adjusted OR [aOR] = 4.18; 95% CI: 2.11, 8.25) but were not more likely to report having had a crash or citation (aOR = 1.36; 95% CI: 0.70, 2.66) in the past year. Users and non-users had similar scores on self-rated abilities for safe driving (adjusted beta=-0.04; 95% CI: -0.23, 0.15) and on driving-related lapses, errors and violations in the past year (adjusted beta = 0.04; 95% CI: -0.04, 0.12). Further study is needed to establish driving risks and behaviours related to cannabis use, independent of other associated risk factors, among older adults.

Perceptions of driving after marijuana use compared to alcohol use among rural American young adults

INTRODUCTION AND AIMS

Substance use contributes to motor vehicle crashes, the leading cause of death among young adults. The current qualitative study examined perceptions of the acceptability and harms associated with driving after marijuana versus alcohol use in rural America. Illuminating rural perspectives is critical given that the motor vehicle fatality rate is twice as high in rural as in urban areas in the USA.

DESIGN AND METHODS

In 2015-2016, 72 young adults aged 18-25 years (Mage  = 20.2; 50.7% female) living in Montana, USA, participated in 11 focus groups. A list of descriptive codes was generated inductively and two individuals coded participant comments. Discussion, memoing and concept mapping were used to uncover broader themes and transcripts were reviewed for evidence of these themes.

RESULTS

There was shared consensus that, with regard to crash risk, driving after marijuana use was safer than driving after alcohol use. While alcohol was thought to impair driving ability universally, marijuana's impacts depended on individual characteristics (e.g. compensatory behaviours) and the marijuana itself (e.g. type). Participants expressed conflicting beliefs about policies surrounding marijuana use and driving but were more knowledgeable about alcohol-related policies. Participants viewed older adults and those in frontier areas as more disapproving of driving after marijuana use.

DISCUSSION AND CONCLUSIONS

Misinformation about the consequences of driving after marijuana use is common, demonstrating the need for future research and educational interventions. Developing and disseminating guidelines for driving after marijuana use would help marijuana users make informed decisions and mitigate driving-related risks.