Association of State Recreational Marijuana Laws With Adolescent Marijuana Use

Evaluation of State Cannabis Laws and Rates of Self-harm and Assault

Importance

State cannabis laws are changing rapidly. Research is inconclusive about their association with rates of self-harm and assault. Existing studies have not considered variations in cannabis commercialization across states over time.

Objective

To evaluate the association of state medical and recreational cannabis laws with self-harm and assault, overall and by age and sex, while considering varying degrees of commercialization.

Design, Setting, and Participants

Using a cohort design with panel fixed-effects analysis, within-state changes in claims for self-harm and assault injuries before and after changes in cannabis laws were quantified in all 50 US states and the District of Columbia. Comprehensive claims data on commercial and Medicare Advantage health plan beneficiaries from January 1, 2003, to December 31, 2017, grouped by state and month, were evaluated. Data analysis was conducted from January 31, 2020, to January 21, 2021.

Exposures

Categorical variable that indexed the degree of cannabis legalization in each state and month based on law type (medical or recreational) and operational status of dispensaries (commercialization).

Main Outcomes and Measures

Claims for self-harm and assault injuries based on International Classification of Diseases codes.

Results

The analysis included 75 395 344 beneficiaries (mean [SD] age, 47 [22] years; 50% female; and median follow-up, 17 months [interquartile range, 8-36 months]). During the study period, 29 states permitted use of medical cannabis and 11 permitted recreational cannabis. Point estimates for populationwide rates of self-harm and assault injuries were higher in states legalizing recreational cannabis compared with states with no cannabis laws, but these results were not statistically significant (adjusted rate ratio [aRR] assault, recreational dispensaries: 1.27; 95% CI, 0.79-2.03;self-harm, recreational dispensaries aRR: 1.15; 95% CI, 0.89-1.50). Results varied by age and sex with no associations found except for states with recreational policies and self-harm among males younger than 40 years (aRR <21 years, recreational without dispensaries: 1.70; 95% CI, 1.11-2.61; aRR aged 21-39 years, recreational dispensaries: 1.46; 95% CI, 1.01-2.12). Medical cannabis was generally not associated with self-harm or assault injuries populationwide or among age and sex subgroups.

Conclusions and Relevance

Recreational cannabis legalization appears to be associated with relative increases in rates of claims for self-harm among male health plan beneficiaries younger than 40 years. There was no association between cannabis legalization and self-harm or assault, for any other age and sex group or for medical cannabis. States that legalize but still constrain commercialization may be better positioned to protect younger male populations from unintended harms.

Cannabis Marketing and Problematic Cannabis Use Among Adolescents

OBJECTIVE

Health consequences of commercializing nonmedical cannabis remain unclear, but data suggest that youth may encounter unintended risks. This study examined whether cannabis marketing exposure and engagement are associated with problematic cannabis use among adolescents.

METHOD

The analytic sample included 172 lifetime cannabis users (15-19 years old) who lived in one of six states with legalized nonmedical cannabis in 2018. Predictors included having exposure to or engagement with cannabis marketing on Facebook or Instagram, seeing cannabis billboards, owning/likely to own cannabis-branded merchandise, and reporting a favorite cannabis brand. Logistic regression assessed whether these predictors were associated with weekly cannabis use, high-intensity cannabis use, and cannabis use disorder (CUD).

RESULTS

Adolescents who saw billboards rarely/sometimes had 5 times the odds of CUD, whereas youth who saw them most/all of the time had 7 times the odds of weekly use and 6 times the odds of CUD. Adolescents who owned/were likely to own branded merchandise had nearly 23 times the odds of weekly use, and those with a favorite brand had 3 times the odds of weekly use and CUD. Adolescents who reported seeing promotions on Instagram rarely/sometimes had 85% lower odds of weekly use, and those who saw them most/all of the time had 93% lower odds.

CONCLUSIONS

The ways cannabis businesses market their products, especially branding, may affect patterns of underage cannabis use. Future research should test whether these associations persist in longitudinal designs. In the interim, states should consider an approach that offers youth additional means to protect them from cannabis marketing.

Nonmedical Marijuana Use and Cardiovascular Events: A Systematic Review

INTRODUCTION

Although marijuana use has increased since 2012, the perceived risk of adverse outcomes has decreased. This systematic review summarizes articles that examined the association between nonmedical marijuana use (ie, observed smoking, self-report, or urinalysis) and cardiovascular events in observational or experimental studies of adults aged ≥18.

METHODS

We searched Medline, EMBASE, PsycInfo, CINAHL, Cochrane Library Database, and Global Health from January 1, 1970, through August 31, 2018. Of 3916 citations, 16 articles fit the following criteria: (1) included adults aged ≥18; (2) included marijuana/cannabis use that is self-reported smoked, present in diagnostic coding, or indicated through a positive diagnostic test; (3) compared nonuse of cannabis; (4) examined events related to myocardial infarction, angina, acute coronary syndrome, and/or stroke; (5) published in English; and (6) had observational or experimental designs.

RESULTS

Of the 16 studies, 4 were cohort studies, 8 were case-control studies, 1 was a case-crossover study, 2 were randomized controlled trials, and 1 was a descriptive study. Studies ranged from 10 participants to 118 659 619 hospitalizations. Marijuana use was associated with an increased likelihood of myocardial infarction within 24 hours in 2 studies and stroke in 6 studies. Results of studies suggested an increased risk for angina and acute coronary syndrome, especially among people with a history of a cardiovascular event.

CONCLUSION

This review suggests that people who use marijuana may be at increased risk for cardiovascular events. As states expand new laws permitting marijuana use, it will be important to monitor the effect of marijuana use on cardiovascular disease outcomes, perhaps through the inclusion of data on nonmedical marijuana use in diverse national and local surveillance systems.

Development and validation of an open-source, disposable, 3D-printed in vitro environmental exposure system for Transwell culture inserts

Accessible in vitro models recapitulating the human airway that are amenable to study whole cannabis smoke exposure are needed for immunological and toxicological studies that inform public health policy and recreational cannabis use. In the present study, we developed and validated a novel three-dimensional (3D)-printed in vitro exposure system (IVES) that can be directly applied to study the effect of cannabis smoke exposure on primary human bronchial epithelial cells.

Using commercially available design software and a 3D printer, we designed a four-chamber Transwell insert holder for exposures to whole smoke. COMSOL Multiphysics software was used to model gas distribution, concentration gradients, velocity profile and shear stress within IVES. Following simulations, primary human bronchial epithelial cells cultured at the air–liquid interface on Transwell inserts were exposed to whole cannabis smoke using a modified version of the Foltin puff procedure. Following 24 h, outcome measurements included cell morphology, epithelial barrier function, lactate dehydrogenase (LDH) levels, cytokine expression and gene expression.

Whole smoke delivered through IVES possesses velocity profiles consistent with uniform gas distribution across the four chambers and complete mixing. Airflow velocity ranged between 1.0 and 1.5 µm·s⁻¹ and generated low shear stresses (<<1 Pa). Human airway epithelial cells exposed to cannabis smoke using IVES showed changes in cell morphology and disruption of barrier function without significant cytotoxicity. Cannabis smoke elevated interleukin-1 family cytokines and elevated CYP1A1 and CYP1B1 expression relative to control, validating IVES smoke exposure impacts in human airway epithelial cells at a molecular level.

The growing legalisation of cannabis on a global scale must be paired with research related to potential health impacts of lung exposures. IVES represents an accessible, open-source, exposure system that can be used to model varying types of cannabis smoke exposures with human airway epithelial cells grown under air–liquid interface culture conditions.

Development of an open-source, disposable, 3D-printed in vitro environmental exposure system for Transwell culture inserts that can be used for environmental exposures important for lung health, and validation with cannabis smoke exposurehttps://bit.ly/2JjgDrm

Marijuana legalization and disability claiming

We study the effect of recent legalization of recreational marijuana use laws (RMLs) in the United States on new applications and allowances for Social Security Disability Insurance and Supplemental Security Income over the period 2001-2019. We combine administrative caseload data from the Social Security Administration with state policy changes using two-way fixed-effects methods. We find that RML adoption increases applications for both benefits. However, there is no change in allowances post-RML. We provide suggestive evidence that the observed changes in applications post-RML are driven by increases in marijuana misuse and selective migration, and decreases in unemployment.

Adolescent drug use initiation and transition into other drugs: A retrospective longitudinal examination across race/ethnicity

BACKGROUND

Understanding adolescent drug use mechanisms is critical for drug use prevention. Although some theories such as the gateway theory suggest that drug users gradually transition into using more addictive drugs, there is no consensus about such a hypothesis. One important factor that hinders the advancement of knowledge in this area is the scarcity of longitudinal studies examining the type of drugs adolescents initially use and the different pathways adolescents take to transition into using other drugs as they grow older.

METHODS

Using the pooled sample of adolescent dug users (14-17 years old; n = 10,644) from the National Survey on Drug Use and Health (2015-2018), we constructed longitudinal data on adolescents' illicit drug use history other than the use of tobacco and alcohol based on the age of drug initiation. This allowed us to investigate what drugs were initially used by adolescents, how the use of these drugs may have progressed into a new drug, and whether there were racial/ethnic differences in the initiation and progression. The retrospective longitudinal data analyses applied life table method and Cox regression models.

RESULTS

Two thirds of the adolescent drug users initiated their drug use trajectories with marijuana, one quarter with inhalants, and the remaining with hallucinogens, prescription drugs, and hard drugs. Adolescent drug users who initiated with different drugs showed unique trajectories to the use of a new drug. By year 8, the probability of using a new drug was about 40% and 70% to 80% for adolescents who initiated with inhalants and other drugs, respectively. The probability of using a new drug for adolescents who initiated with marijuana and inhalants accumulated stably over time, and its difference with that of other drug users diminished over time. The multivariate Cox regression models suggest the observed discrepancies generally held after controlling for covariates. There were also racial/ethnic differences in adolescent drug use initiation and progression, with Black/African American adolescents being the least likely to switch to the use of a new drug.

CONCLUSION

Adolescents' initial use of marijuana and inhalants may lead to substantial risks of using other drugs over time. It is therefore important to screen adolescent drug use comprehensively and provide early interventions to prevent an escalation to more detrimental drugs. The findings provide new evidence to support aspects of both the gateway and generalized risk drug use theories.

No evidence of associations between genetic liability for schizophrenia and development of cannabis use disorder

BACKGROUND

Cannabis use and cannabis use disorder (CUD) is increased in patients with schizophrenia. It is important to establish if this is explained by non-causal factors, such as shared genetic vulnerability. We aimed to investigate whether the polygenic risk scores (PRS) for schizophrenia and other psychiatric disorders would predict CUD in controls, patients with schizophrenia, and patients with other psychiatric disorders.

METHODS

We linked nationwide Danish registers and genetic information obtained from dried neonatal bloodspots in an observational analysis. We included people with schizophrenia, other psychiatric disorders, and controls. The exposures of interest were the PRS for schizophrenia, attention-deficit hyperactivity disorder (ADHD) autism spectrum disorder, and anorexia nervosa. The main outcome of interest was the diagnosis of CUD.

RESULTS

The study included 88 637 individuals. PRS for schizophrenia did not predict CUD in controls [hazard ratio (HR) = 1.16, 95% CI 0.95-1.43 per standard-deviation increase in PRS, or HR = 1.47, 95% CI 0.72-3.00 comparing highest v. remaining decile], but PRS for ADHD did (HR = 1.27, 95% CI 1.08-1.50 per standard-deviation increase, or HR = 2.02, 95% CI 1.27-3.22 for the highest decile of PRS). Among cases with schizophrenia, the PRS for schizophrenia was associated with CUD. While CUD was a strong predictor of schizophrenia (HR = 4.91, 95% CI 4.36-5.53), the inclusion of various PRS did not appreciably alter this association.

CONCLUSION

The PRS for schizophrenia was not associated with CUD in controls or patients with other psychiatric disorders than schizophrenia. This speaks against the hypothesis that shared genetic vulnerability would explain the association between cannabis and schizophrenia.

Assessing New Zealand's Cannabis Legalization and Control Bill: prospects and challenges

BACKGROUND

Few countries have developed detailed legislative proposals for legalizing cannabis. New Zealand recently released the Cannabis Legalization and Control Bill (CLCB) that will be the subject of a referendum in September 2020.

AIMS

To assess the CLCB, drawing on emerging evidence from cannabis legalization overseas, public health research on alcohol and tobacco and the attempt to establish a regulated market for 'legal highs' in New Zealand.

DISCUSSION

The CLCB proposes a strictly regulated commercial cannabis market that resembles the Canadian approach, but notably without on-line sales or regional heterogeneity in retail distribution. The objective of the CLCB of lowering cannabis use over time appears at odds with the largely commercial cannabis sector that will focus on expanding sales. The CLCB includes provision for home cultivation and social benefit operators, but it is not clear what priority these operators will receive. A potency cap of 15% tetrahydrocannabinol (THC) for cannabis plants is included, and this is at the high end of black-market cannabis. The proposed progressive product tax based on THC will be challenging to implement. There is no formal minimum price, but rather discretionary powers to raise the excise if the price drops too much. The CLCB includes a comprehensive ban on advertising, but non-conventional on-line promotion will be difficult to suppress. The central government cannabis authority is tasked with developing local retail outlet policies. We caution against the temptation to employ an interim regulatory regime following a positive referendum result, because a partially regulated market will expose users to health risks and undermine public support.

CONCLUSIONS

New Zealand's Cannabis Legalization and Control Bill's objective of reducing cannabis use via a commercial market will be challenging to achieve. The bill could be strengthened with formal minimum pricing, lower potency cap and greater clarity concerning social benefit operators and the role of local government.

Retail Availability of Recreational Marijuana and Alcohol in Oregon Counties and Co-Use of Alcohol and Marijuana and Related Beliefs among Adolescents

Objective: We investigated whether recreational marijuana legalization (RML) in Oregon in 2015 and recreational marijuana and alcohol retail outlet density levels in Oregon counties were associated with increased alcohol and marijuana co-use and beliefs supportive of alcohol and marijuana use among adolescents. Method: We conducted secondary analyses of biennial data collected from 11th graders who participated in the Student Wellness Survey (SWS) in 36 Oregon counties from 2010 to 2018 (N = 71,870). Multi-level logistic regression analyses assessed changes in past-30-day co-use of alcohol and marijuana, and alcohol- and marijuana-related beliefs after RML in counties with low, medium, and high densities of licensed recreational marijuana and alcohol retail outlets. We used post-RML 2016 and 2018 SWS data to examine whether beliefs accounted for any relationship of recreational marijuana and alcohol outlet density with alcohol and marijuana co-use. Results: We found a significant post-RML increase in past-30-day alcohol and marijuana co-use in 2016 in counties with the highest density of recreational marijuana and alcohol retail outlets. There were significant post-RML increases in perceived risk and parent approval of alcohol and marijuana use. Analyses with 2016 and 2018 SWS data indicated that the relationship between level of recreational marijuana and alcohol retail outlet density and past-30-day alcohol and marijuana co-use was accounted for beliefs about marijuana and alcohol availability, approval by parents, and risk. Conclusion: RML and greater retail availability of recreational marijuana and alcohol were positively associated with alcohol and marijuana co-use among adolescents, and with beliefs favorable to alcohol and marijuana use.

Assessment of Prescription Opioid Medical Use and Misuse Among Parents and Their Adolescent Offspring in the US

Importance

Limited information is available regarding the association between parental and adolescent medical prescription opioid use and misuse in the US.

Objective

To examine the associations between parental and adolescent prescription opioid medical use and misuse.

Design, Setting, and Participants

This cross-sectional, nationally representative study included 15 200 parent-adolescent dyads from the annual 2015-2017 National Survey on Drug Use and Health. Data were collected from January 6, 2015, to December 20, 2017, and analyzed from October 4, 2019, to October 15, 2020.

Exposures

Parental past 12-month exclusive medical prescription opioid use and any misuse (ie, using without a prescription or in any way not directed by a physician).

Main Outcomes and Measures

Adolescent past 12-month medical prescription opioid use or misuse. Multivariable regressions estimated associations between parental and offspring medical prescription opioid use or misuse, controlling for sociodemographic and psychosocial variables.

Results

Respondents included 9400 mother-child and 5800 father-child dyads in the same household; children were aged 12 to 17 years (52.8% male; mean [SD] age, 14.5 [1.7] years). Controlling for other factors, parental medical prescription opioid use was associated with adolescent prescription opioid medical use (adjusted odds ratio [aOR], 1.28; 95% CI, 1.06-1.53) and misuse (aOR, 1.53; 95% CI, 1.07-2.25), whereas parental misuse was not. Parental medical prescription stimulant use was associated with adolescent medical prescription opioid use (aOR, 1.40; 95% CI, 1.02-1.91). Parental marijuana use (aOR, 1.84; 95% CI, 1.13-2.99), parent-adolescent conflict (aOR, 1.26; 95% CI, 1.05-1.52), and adolescent depression (aOR, 1.75; 95% CI, 1.26-2.44) were associated with adolescent prescription opioid misuse. Adolescent delinquency (aOR, 1.55; 95% CI, 1.38-1.74) and perceived schoolmates' drug use (aOR, 2.87; 95% CI, 1.95-4.23) were also associated with adolescent misuse and more weakly with medical use (aORs, 1.13 [95% CI, 1.05-1.22] and 1.61 [95% CI, 1.32-1.96], respectively).

Conclusions and Relevance

Youth use of prescription opioids is in part a structural/environmental issue. The findings of this study suggest that parental medical prescription opioid use is associated with offspring prescription opioid use, whereas parental misuse is not. Restricting physicians' opioid prescribing to parents is a crucial public health goal. In addition, parents could be educated on the risks of their prescription opioid use for offspring and on practices to mitigate risk, including safe medication storage and disposal. Screening for parental prescription opioid use could be part of pediatric practice. Addressing adolescent mental health could also reduce adolescent prescription opioid misuse.

Children's Knowledge of Cannabis and Other Substances in States with Different Cannabis Use Regulations

Background: Public acceptance of cannabis continues to increase across the US, yet there has been little research on how cannabis legalization affects young children. The present study compared knowledge of cannabis and other substances among children living in states with different cannabis laws and examined whether the association between such substance knowledge and externalizing behavior varies by state cannabis regulations. Methods: Participants were from the Adolescent Brain Cognitive Development^SM Study (ABCD Study®) at the baseline assessment (N = 11,875, ages 9-11, collected from 2016 to 2018). Chi-square difference tests were used to compare nested models testing group differences in knowledge of substances and the association between externalizing disorder/behavior and substance knowledge as a function of state legality of cannabis use (recreational, medical, low THC/CBD, none). Results: Children living in states with more permissive cannabis laws had a greater knowledge of cannabis and reported more alcohol experimentation. In contrast, knowledge regarding alcohol, tobacco, and other illicit drugs was not greater in children from states with more permissive cannabis laws. Externalizing disorder/behavior was not significantly associated with cannabis knowledge in any group and not significantly different across groups. The association between externalizing disorder/behavior and illicit drug knowledge was significant only in states with the recreational and medical use laws but did not differ significantly across groups. Conclusion: Children living in environments with more permissive cannabis regulations have greater knowledge of cannabis, but not other substances, and report more experimentation with alcohol.

Mode of Marijuana Use among Young Adults: Perceptions, Use Profiles, and Future Use

BACKGROUND

Given changes in marijuana regulations, retail, and products and potential impact on use, we examined young-adult perceptions of different modes of use, the proportion using via different modes (e.g. smoking, vaping, ingesting), and associations with the use levels and stability of use over time.

METHODS

We analyzed baseline and one-year follow-up survey data (Fall 2018-2019) among 3,006 young adults (ages 18-34) across six metropolitan areas (Atlanta, Boston, Minneapolis-St. Paul, Oklahoma City, San Diego, Seattle). Measures included marijuana use frequency and mode, sociodemographics, other substance use, and social influences.

RESULTS

Participants' rated the following modes of use as: least harmful/addictive: topicals, oral pills, joint/bowl; most socially acceptable: joint/bowl, edibles/beverages, vaporized; and most harmful/addictive and least acceptable: wrapped, vaped, or waterpipe/bong with tobacco. Baseline past-month use prevalence was 39.2% (n = 1,178). Most frequent use mode was smoking (joints/bowls/cigar papers; 54.0%), vaping (21.8%), via pipe/bong (15.1%), and ingesting (9.1%). Multinomial logistic regression indicated that participants in states with legalized marijuana retail were at greater odds for using via modes other than smoking; participants more frequently using were at greater odds for using via pipe/bong (vs. smoking) (ps < .001). Regarding most frequent mode across time, most consistent was pipe/bong (53.3%), followed by smoking (49.3%), vaping (44.5%), and ingesting (32.9%). Past-month abstinence at follow-up was most common among those originally ingesting (34.3% abstinent), followed by smoking (23.6%), vaping (18.8%), and pipe/bong (14.8%).

CONCLUSIONS

Ongoing surveillance is needed to understand marijuana use patterns over time across different user groups (particularly by mode) and to inform interventions promoting abstinence.

Recreational Marijuana Legalization and Use Among California Adolescents: Findings From a Statewide Survey

OBJECTIVE

The legalization of recreational marijuana use and retail sales raises concerns about possible effects on marijuana use among adolescents. We evaluated the effects of recreational marijuana legalization (RML) in California in November 2016 on use among adolescents and investigated subgroup differences in these effects.

METHOD

We analyzed data from successive cross-sectional samples of 7th, 9th, and 11th grade students (N = 3,330,912) who participated in the California Healthy Kids Survey from 2010-2011 to 2018-2019. Participants reported grade, sex, ethnicity, race, and lifetime and past-30-day marijuana use.

RESULTS

Multilevel analyses showed that RML was associated with increases in the likelihood of lifetime (odds ratio = 1.18, 95% CI [1.15, 1.21], p < .01) and past-30-day marijuana use (odds ratio = 1.23, 95% CI [1.20, 1.26], p < .01) relative to previous downward trends. RML was more strongly associated with increases in prevalence of marijuana use among 7th versus 9th and 11th graders, females versus males, non-Hispanic versus Hispanic youth, and White versus African American, American Indian/Native Alaskan, and multiracial youth. Overall, RML was not significantly associated with frequency of past-30-day use among users, although stronger positive associations between RML and frequency of use were found for 11th graders, Asian Americans, and African Americans. The association was weaker for females.

CONCLUSIONS

RML in California was associated with an increase in adolescent marijuana use in 2017-2018 and 2018-2019. Demographic subgroup differences in these associations were observed. Evidence-based prevention programs and greater local control on retail marijuana sales may help to reduce marijuana availability and use among adolescents.

Prevalence and Correlates of Medicinal Cannabis Use Among Adolescents

PURPOSE

Prior studies of medicinal cannabis use (MCU) have focused primarily on adults. This study examined the prevalence and correlates of self-reported MCU among adolescents.

METHODS

Secondary school students (grades 9-12; N = 3,221) completed a cross-sectional survey in classrooms across Ontario, Canada, in 2016-2017. Participants reported on cannabis use behavior, cannabis dependence, other drugs use, and general health and sleep. Participants reporting cannabis use in the past year were grouped based on whether they reported MCU or not (i.e., recreational cannabis use only [RCU-only]).

RESULTS

An estimated 6.89% (95% confidence interval 5.48%-8.63%) of students reported MCU, representing one quarter of the students reporting current cannabis use. Relative to the RCU-only group, the MCU group reported using cannabis more frequently, were more likely to report vaping and eating cannabis, had greater risk for cannabis dependence, perceived cannabis as less harmful, were more likely to report tobacco use, recreational use of other drugs, and medicinal use of sedatives or tranquilizers, and were less likely to report good health and sleeping for seven or more hours per night. Frequency of cannabis use accounted for differences between MCU and RCU-only groups in cannabis dependence risk, recreational use of other drugs, and perceiving cannabis as harmful, but it did not account for the other differences.

CONCLUSIONS

A sizable portion of secondary school students report MCU, which appears to be associated with more frequent cannabis use and certain substance use and health-related correlates. Research is needed to further characterize motives for self-reported MCU among adolescents.

Has Cannabis Use Among Youth Increased After Changes in Its Legal Status? A Commentary on Use of Monitoring the Future for Analyses of Changes in State Cannabis Laws

As US states move toward various forms of adult access to cannabis, there has been a great interest in measuring the impact of such changes on adolescent cannabis use. Two recent prominent analyses have used Monitoring the Future (MTF), a nationally representative survey of students, to examine the effects. We compared MTF data for California and for Washington State with other survey data on use by adolescents in those states. In both studies, findings based on MTF were different from those using other larger, state-representative surveys. The discrepancy reflects the high within-state variation in prevalence rates and the small number of schools in MTF state samples. Using the Washington Health Youth Survey, we estimate that after recreational cannabis legalization past 30-day cannabis use prevalence in grade 8 decreased by 22.0%, in grade 10 prevalence decreased by 12.7%, and no effect in grade 12. These trends are consistent with those in states without recreational cannabis laws, suggesting that legalization did not impact adolescent use prevalence. Long-term trends in MTF are consistent with other data, but year-to-year volatility in state-level series undermines the survey's suitability for evaluation of state cannabis policy changes. Survey-based analyses at the state level need to be cross-validated with findings from other data sources. When findings are disparate and methodological rigor is equivalent, analyses of data sources specifically designed to describe state-level phenomena are more credible.

Analysis of US Teen Driving After Using Marijuana, 2017

This cross-sectional study examines the prevalence of and factors associated with driving after using marijuana among US adolescents.

Examining Sex and Racial/Ethnic Differences in Co-use of Alcohol, Cannabis, and Cigarettes in a Community Sample of Adolescents

INTRODUCTION

Although adolescents often co-use alcohol, cigarettes, and cannabis, little is known about sex and racial/ethnic differences in the co-use of these substances. Therefore, this investigation examined sex and racial/ethnic differences in alcohol, cigarette, and cannabis co-use in a large and ethnically diverse group. Methods: Participants were drawn from a large, multi-site study of adolescents from three regions in the United States (N = 4,129; Mage=16.10 years, SD = 0.59; 51% female, 49% male; 37% Black, 37% Hispanic, 25% White). Participants were categorized into eight mutually exclusive groups based on their self-reported use of alcohol, cannabis, and cigarettes in the last 30 days. Results: Unadjusted multinomial logistic regression revealed that males were more likely than females to use cannabis-only and to co-use all three substances. Additionally, Black and Hispanic adolescents were more likely to use cannabis-only, while White adolescents were more likely than Black and Hispanic adolescents to co-use alcohol and cigarettes. After adjusting for other sociodemographic variables (age, household income, parental education, and parent marital status), males were more likely to use cannabis-only than females; White youth were more likely than Hispanic youth to use cigarettes only and co-use cigarettes and alcohol. White youth were more likely than Black youth to co-use alcohol and cigarettes and co-use all three substances. Discussion: These results indicate sex and racial/ethnic differences in substance co-use that were not explained by socioeconomic factors. Results of this work suggest potential strategies for targeted prevention efforts and underscore the importance of continued efforts to better understand patterns of alcohol and substance co-use.

Sweetening the pot: Exploring differences between frequent gamblers who do and do not gamble under the influence of cannabis

The legalization of recreational cannabis for adults is becoming more common across the United States of America, as well as other counties around the world. Previous research has documented shared risk factors between cannabis use and gambling. Experimental studies have shown cognitive effects of cannabis that might influence gambling behavior. The current study explored demographics, gambling behaviors, and mental health differences based on the degree to which individuals use cannabis while they gamble. Individuals (N = 805) who gambled at least weekly completed an online survey. Thirty percent reported gambling under the influence of cannabis. Of these individuals, 41% reported using cannabis 25% of the time that they gambled, 31% reported being under the influence 50% of the time when gambling, 16% were under the influence 75% of the time when gambling, and 13% reported always or almost always gambling under the influence of cannabis. Those who reported gambling while under the influence of cannabis were more likely to be younger, non-white and non-heterosexual. They also reported higher levels of psychological distress, were more likely to have had a diagnosis of ADHD and a history of treatment for gambling, substance use, or other kinds of mental health concerns. Individuals who used cannabis while gambling also reported gambling more frequently than those who did not. This study provides one of the first explorations into who uses cannabis while gambling. Future experimental studies are required to investigate the direct effects of cannabis on gambling behaviors.

Self-reported driving after marijuana use in association with medical and recreational marijuana policies

BACKGROUND

A common concern surrounding increasingly permissive marijuana policies in the US is that they will lead to more dangerous behavior, including driving after marijuana use. Although there is considerable research on the effects of marijuana policies on behaviours, few studies have examined self-reported driving after marijuana use. In this study, we use data from the Traffic Safety Culture Index (TSCI) to model self-reported past-year driving after marijuana use in association with medical and recreational marijuana policies.

METHODS

We analysed individual responses to annual administrations of TSCI from years 2013-2017 using a multiple logistic regression model. Our outcome variable was self-reported past-year driving after marijuana use (at least once vs. never), and our primary explanatory variable was the respondents' state medical marijuana (MM) and recreational marijuana (RM) policy. Additional explanatory variables include policies that specify thresholds for marijuana-intoxicated driving, year, and demographic factors.

RESULTS

Drivers in states that legalized MM but not RM had marginally higher odds of self-reporting driving after marijuana use compared to drivers in states where both RM and MM were illegal (adjusted OR 1.29; 95% CI 0.98, 1.70; p = 0.075). However, we found little evidence that drivers in states that legalized both RM and MM had higher odds of driving after marijuana use compared to drivers in states where both RM and MM were illegal (adjusted OR 1.06; 95% CI 0.71, 1.56; p = 0.784). Per-se or THC threshold laws were associated with lower self-reported driving after marijuana use (adjusted OR 0.74; 95% CI 0.57, 0.95; p = 0.018).

CONCLUSION

Although we found some evidence of an association between MM legalization and self-reported driving after marijuana use, our results provide only mixed support for the hypothesis that permissive marijuana policies are associated with higher odds of self-reported driving after marijuana use.

The Influence of Recreational Substance Use in TMS Research

(1) Background: Transcranial magnetic stimulation (TMS) approaches are widely used to study cortical and corticospinal function. However, responses to TMS are subject to significant intra-and inter-individual variability. Acute and chronic exposure to recreational substances alters the excitability of the sensorimotor system and may contribute to the variability in TMS outcome measures. The increasing prevalence of recreational substance use poses a significant challenge for executing TMS studies, but there is a lack of clarity regarding the influence of these substances on sensorimotor function. (2) Methods: The literature investigating the influence of alcohol, nicotine, caffeine and cannabis on TMS outcome measures of corticospinal, intracortical and interhemispheric excitability was reviewed. (3) Results: Both acute and chronic use of recreational substances modulates TMS measures of excitability. Despite the abundance of research in this field, we identify knowledge gaps that should be addressed in future studies to better understand the influence of these substances on TMS outcomes. (4) Conclusions: This review highlights the need for TMS studies to take into consideration the history of participant substance use and to control for acute substance use prior to testing.

Cannabis-related Hospitalizations Among Youth in Canada Before and After Cannabis Legalization

OBJECTIVES

We investigated trends in cannabis-related hospitalizations among youth before and after legalization of recreational cannabis in Canada on October 17, 2018.

METHODS

We computed rates of cannabis-related hospitalizations and the proportion of substance-related hospitalizations involving cannabis by age and sex in the months before and after legalization in Quebec, Canada.

RESULTS

In boys aged 10 to 14 years, cannabis-related hospitalization rates increased from 5.2 per 100,000 one year before legalization [95% confidence interval (CI) 2.9-9.3] to 9.5 per 100,000 after legalization (95% CI 6.2-14.6), although the increase was not statistically significant. Cannabis was reported in 39.3% of substance-related hospitalizations in boys aged 10 to 14 years before legalization, compared with 70.0% after legalization, representing a difference of 30.7% (95% CI 2.8-58.6). There was no increase in cannabis-related hospitalizations among girls or boys aged 15 to 19 years.

CONCLUSIONS

This study suggests that cannabis legalization in Canada did not increase the risk of short-term cannabis-related hospitalization among girls and older boys. However, legalization may have contributed to an increase in the risk in boys under 15 years. Further data are needed to clarify trends after legalization for younger adolescents.

Cannabis knowledge and implications for health: Considerations regarding the legalization of non-medical cannabis

Cannabis contains over a hundred of different cannabinoids, of which Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most well studied. The use of high-potency cannabis, containing high concentrations of THC and low concentrations of CBD, has been linked to adverse health outcomes, particularly for adolescents and young adults. Recently, an increase in cannabis potency has been observed in jurisdictions that legalized the sale of cannabis for non-medical purposes. Moreover, an increase of cannabis use and cannabis-related emergency treatment have also been observed in these jurisdictions. At the same time, risk perception regarding cannabis use has decreased in these populations. Trivializing language and an increased appearance of commercial cannabis in the public space may lead to a generalized underestimation of the risks of cannabis use. New regulation models principally focus on the creation of a legal cannabis market economy, the diversion of profits from illegal markets, and the reduction of costs associated with prohibition. However, an approach that specifically focuses on the rights to the health and safety of the individual should be considered in order to reduce the risks associated with cannabis legalization. Such an approach should promote and protect individual and social health and safety, establish a strict quality control of legal cannabis products regulated according to THC and CBD content, and eliminate all sorts of incentives to use, thus providing a more consistent, sustainable, and ethical framework for the legalization of non-medical cannabis use.

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.

The association between recreational cannabis commercialization and cannabis exposures reported to the US National Poison Data System

BACKGROUND AND AIMS

Recreational cannabis has been legalized in 11 states and District of Columbia (DC) in the United States. Among these, 10 states further permitted retail sale to provide a legal supply to adults. This study examined the associations of cannabis exposures with recreational cannabis legalization and commercialization.

DESIGN

Secondary data analysis of state-quarter level cannabis exposures during 2010-17 in the United States. Linear regressions with a difference-in-differences design were used to compare pre- and post-legalization trends in states that legalized recreational cannabis to contemporaneous trends in states that did not legalize recreational cannabis.

SETTING

United States, including all 50 states and DC.

CASES

Cannabis exposures reported to the US National Poison Data System.

MEASUREMENTS

The primary outcome was state age-adjusted cannabis exposures reported to the US National Poison Data System per 1 000 000 population per quarter. The two policy variables of interest included (1) the enactment of recreational cannabis legalization (i.e. removing penalties for adults' possession of cannabis in a small amount for recreational use) and (2) the initiation of recreational cannabis commercialization (i.e. providing a legal supply of cannabis to adults through licensed dispensaries).

FINDINGS

The association between a state's enactment of recreational cannabis legalization and its changes in cannabis exposures was statistically non-significant overall. After controlling for recreational cannabis legalization, however, the initiation of recreational cannabis commercialization was associated with 5.06-5.80 more exposures per 1 000 000 population per quarter (67-77% increase relative to the pre-legalization average), depending on the composition of comparison states. The increase associated with commercialization was higher among minors than adults (7.97-9.53 versus 3.83-4.21 more exposures), higher among males than females (6.16-7.56 versus 3.76-3.91 more exposures) and higher among exposures with medical consequences than those without medical consequences (4.09-4.79 versus 0.97-1.01 more exposures).

CONCLUSION

An increase in cannabis exposures reported to the US National Poison Data System was observed following recreational cannabis commercialization in the United States.

Cannabis-related driving and passenger behaviours among high school students: a cross-sectional study using survey data

BACKGROUND

Many youth report driving under the influence of cannabis (DUIC) and riding with a cannabis-impaired driver (RWCD), and many perceive that cannabis causes limited impairment. We examined associations of perceived risk of regular cannabis use with DUIC and RWCD, exploring differences by sex and rural setting.

METHODS

In a cross-sectional study, we examined DUIC and RWCD among high school students in grades 11 and 12 who participated in the 2016-2017 Canadian Student Tobacco, Alcohol and Drugs Survey. Private and public schools across 9 Canadian provinces were included. New Brunswick and the 3 territories were not included. Multinomial logistic regression models generated adjusted and unadjusted models for the associations.

RESULTS

A total of 52 103 students in grades 7-12, from 117 school boards and 699 schools, participated in the survey. The survey response rate was 76.2% (n = 52 103/68 415). In total, 14 520 students in grades 11 and 12 participated in the survey. Greater perceived risk of regular cannabis use was associated with reduced risk of DUIC and RWCD in a dose-response manner. Students perceiving that regular cannabis use posed great risk had an adjusted relative risk (RR) of 0.06 (95% confidence interval [CI] 0.04-0.10) of DUIC in the past 30 days compared with students perceiving that regular use posed no risk. Students perceiving that regular cannabis use posed great risk had an adjusted RR of 0.09 (95% CI 0.07-0.12) of RWCD in the past 30 days compared with students perceiving no such risk. Associations were consistent for male and female students and for those living in urban and rural areas.

INTERPRETATION

Students perceiving minimal risk from cannabis use reported greater engagement in cannabis-related risky driving behaviours. Given the importance of youth perceptions in shaping driving and passenger behaviours, efforts must be made to disseminate appropriate information regarding cannabis-related driving risks to high school students.

Difference-in-Difference in the Time of Cholera: a Gentle Introduction for Epidemiologists

Purpose of review

The goal of this article is to provide an introduction to the intuition behind the difference-in-difference method for epidemiologists. We focus on the theoretical aspects of this tool, including the types of questions for which difference-in-difference is appropriate, and what assumptions must hold for the results to be causally interpretable.

Recent findings

While currently under-utilized in epidemiologic research, the difference-in-difference method is a useful tool to examine effects of population-level exposures, but relies on strong assumptions.

Summary

We use the famous example of John Snow's investigation of the cause of cholera mortality in London to illustrate the difference-in-difference approach and corresponding assumptions. We conclude by arguing that this method deserves a second-look from epidemiologists interested in asking causal questions about the impact of a population-level exposure change on a population-level outcome for the group that experienced the change.

Impact evaluations of drug decriminalisation and legal regulation on drug use, health and social harms: a systematic review

OBJECTIVES

To review the metrics and findings of studies evaluating effects of drug decriminalisation or legal regulation on drug availability, use or related health and social harms globally.

DESIGN

Systematic review with narrative synthesis.

DATA SOURCES

We searched MEDLINE, Embase, PsycINFO, Web of Science and six additional databases for publications from 1 January 1970 through 4 October 2018.

INCLUSION CRITERIA

Peer-reviewed articles or published abstracts in any language with quantitative data on drug availability, use or related health and social harms collected before and after implementation of de jure drug decriminalisation or legal regulation.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers screened titles, abstracts and articles for inclusion. Extraction and quality appraisal (modified Downs and Black checklist) were performed by one reviewer and checked by a second, with discrepancies resolved by a third. We coded study-level outcome measures into metric groupings and categorised the estimated direction of association between the legal change and outcomes of interest.

RESULTS

We screened 4860 titles and 221 full-texts and included 114 articles. Most (n=104, 91.2%) were from the USA, evaluated cannabis reform (n=109, 95.6%) and focussed on legal regulation (n=96, 84.2%). 224 study outcome measures were categorised into 32 metrics, most commonly prevalence (39.5% of studies), frequency (14.0%) or perceived harmfulness (10.5%) of use of the decriminalised or regulated drug; or use of tobacco, alcohol or other drugs (12.3%). Across all substance use metrics, legal reform was most often not associated with changes in use.

CONCLUSIONS

Studies evaluating drug decriminalisation and legal regulation are concentrated in the USA and on cannabis legalisation. Despite the range of outcomes potentially impacted by drug law reform, extant research is narrowly focussed, with a particular emphasis on the prevalence of use. Metrics in drug law reform evaluations require improved alignment with relevant health and social outcomes.

Marijuana Legalization and Youth Marijuana, Alcohol, and Cigarette Use and Norms

INTRODUCTION

Rates of adolescent substance use have decreased in recent years. Knowing whether nonmedical marijuana legalization for adults is linked to increases or slows desirable decreases in marijuana and other drug use or pro-marijuana attitudes among teens is of critical interest to inform policy and promote public health. This study tests whether nonmedical marijuana legalization predicts a higher likelihood of teen marijuana, alcohol, or cigarette use or lower perceived harm from marijuana use in a longitudinal sample of youth aged 10-20 years.

METHODS

Data were drawn from the Seattle Social Development Project-The Intergenerational Project, an accelerated longitudinal study of youth followed both before (2002-2011) and after nonmedical marijuana legalization (2015-2018). Analyses included 281 youth surveyed up to 10 times and living in a state with nonmedical marijuana legalization between 2015 and 2018 (51% female; 33% white, 17% African American, 10% Asian/Pacific Islander, and 40% mixed race or other).

RESULTS

Multilevel modeling in 2019 showed that nonmedical marijuana legalization predicted a higher likelihood of self-reported past-year marijuana (AOR=6.85, p=0.001) and alcohol use (AOR 3.38, p=0.034) among youth when controlling birth cohort, sex, race, and parent education. Nonmedical marijuana legalization was not significantly related to past-year cigarette use (AOR=2.43, p=0.279) or low perceived harm from marijuana use (AOR=1.50, p=0.236) across youth aged 10-20 years.

CONCLUSIONS

It is important to consider recent broad declines in youth substance use when evaluating the impact of nonmedical marijuana legalization. States that legalize nonmedical marijuana for adults should increase resources for the prevention of underage marijuana and alcohol use.

Cannabis health knowledge and risk perceptions among Canadian youth and young adults

Abstract

Background

Although recreational cannabis is now legal in Canada, little empirical evidence exists regarding young Canadians’ cannabis literacy, cannabis-related risk perceptions, and risk of different forms of cannabis or the effect that public health education may have on these perceptions. The present study sought to address these knowledge gaps to examine health knowledge and risk perceptions associated with cannabis use.

Methods

An online survey was conducted with a national sample (N = 870) of Canadians aged 16 to 30 years in October 2017 using a commercial panel. The study examined young Canadians’ awareness of negative health effects related to cannabis, evaluation of known risks, and risk perceptions of different forms of administration.

Results

Most respondents were aware of a cannabis-related physical health effect (78.0%). Approximately one-third reported having been exposed to public health messaging about cannabis; digital media was reported most frequently. Compared to never users, ever users were less likely to report general likelihood of addiction (p < 0.001) and harm to mental health (p < 0.001). Approximately one-quarter of past 3-month cannabis users reported they were at least “a little” addicted. Respondents who reported using a particular form of cannabis self-administration (e.g., edibles, smokables) were less likely to perceive harm than those who did not use each form (p < 0.001).

Conclusions

The current study is among the first to measure the knowledge and perceptions of risks of Canadian youth about cannabis. The study, conducted in the time immediately preceding legalization, may serve as a reference point for future studies examining changes in cannabis knowledge and risk perceptions. This will be important in addressing the need for monitoring and enhancing public awareness of the impact and potential harms of this newly legalized substance.

Economic Effects of Adolescent to Adult Patterns of Cannabis Use: Full-Time Employment and Employment Stability

Research has yet to examine stability in employment as a function of cannabis use once an individual transitions into full-time work. Using data from the Rochester Youth Development Study, trajectories of cannabis use spanning ages 14 to 30 were identified among a sample of predominantly minorities (>80%; 68% African American). After hard-classifying individuals by patterns of cannabis use, probabilities of full-time employment and conditional probabilities of full-time employment were calculated and compared across patterns of use. Abstention or rare cannabis use was associated with a higher likelihood of full-time employment compared with other cannabis use patterns. Full-time employment stability was high for each pattern of cannabis use (>89%) and differences decreased with age and prior periods of employment. The results indicate that patterns of cannabis use spanning adolescence to adulthood have limited impact on the ability to retain full-time employment once employed and are interpreted in light of growing legalization of cannabis use.

Marijuana Use Among Justice-Involved Youths After California Statewide Legalization, 2015-2018

Objectives. To determine the impact of California's recreational marijuana legalization on marijuana use among justice system-involved (JSI) adolescents and young adults, and to distinguish whether any changes resulted from legalization (passing the law) or from implementation of the law.Methods. We compared changes in JSI youths' marijuana use in 2 states: California (n = 504), where recreational marijuana use was recently legalized, and Pennsylvania (n = 478), where recreational use is still prohibited. Furthermore, we examined changes in marijuana use across 3 key time periods (October 2015-June 2018): before legalization, after legalization but before implementation, and after implementation.Results. California JSI youths did not demonstrate a significant increase in marijuana use after legalization (b = -0.010; P = .950) or implementation (b = -0.046; P = .846). However, in Pennsylvania, rates of marijuana use increased significantly after legalization (b = 0.602; P = .001) but not after implementation (b = 0.174; P = .533).Conclusions. Although recreational marijuana legalization was not associated with changes in marijuana use among youths in California, we observed increased rates of use in Pennsylvania after legalization in California. Recreational marijuana laws may be indirectly related to youths' marijuana use by supporting more permissive national attitudes toward marijuana.

'Standard THC units': a proposal to standardize dose across all cannabis products and methods of administration

BACKGROUND AND AIMS

Cannabis products are becoming increasingly diverse, and vary considerably in concentrations of ∆⁹ -tetrahydrocannabinol (THC) and cannabidiol (CBD). Higher doses of THC can increase the risk of harm from cannabis, while CBD may partially offset some of these effects. Lower Risk Cannabis Use Guidelines currently lack recommendations based on quantity of use, and could be improved by implementing standard units. However, there is currently no consensus on how units should be measured or standardized among different cannabis products or methods of administration.

ARGUMENT

Existing proposals for standard cannabis units have been based on specific methods of administration (e.g. joints) and these may not capture other methods, including pipes, bongs, blunts, dabbing, vaporizers, vape pens, edibles and liquids. Other proposals (e.g. grams of cannabis) cannot account for heterogeneity in THC concentrations among different cannabis products. Similar to alcohol units, we argue that standard cannabis units should reflect the quantity of primary active pharmacological constituents (dose of THC). On the basis of experimental and ecological data, public health considerations and existing policy, we propose that a 'standard THC unit' should be fixed at 5 mg THC for all cannabis products and methods of administration. If supported by sufficient evidence in future, consumption of standard CBD units might offer an additional strategy for harm reduction.

CONCLUSIONS

Standard ∆⁹ -tetrahydrocannabinol (THC) units can potentially be applied among all cannabis products and methods of administration to guide consumers and promote safer patterns of use.

Impacts de la légalisation du cannabis récréatif sur la santé mentale : une recension des écrits

Objectif Cet article présente une recension des écrits sur l’impact de la légalisation du cannabis récréatif sur la santé mentale et s’inscrit dans le contexte des politiques canadiennes récemment adoptées à cet égard.

Méthode Cette recension a été effectuée dans la base de données PubMed en utilisant la combinaison de termes associés au cannabis, à la légalisation et à la santé mentale. Deux évaluateurs indépendants ont ensuite examiné 272 titres et résumés, puis ont conservé 11 articles.

Résultats À la suite de la révision des articles, nous constatons que la plupart des études ciblant la consommation de cannabis décrivent une prévalence croissante d’utilisateurs. Il est à noter qu’aucune étude n’a démontré une diminution de la consommation du cannabis après la légalisation. Parmi les 11 articles retenus, trois évaluent la perception des risques associés au cannabis (avant et après la légalisation). Deux d’entre eux montrent une diminution des risques perçus après la légalisation, alors que le troisième décrit l’inverse. Quelques études ont également analysé l’impact de la légalisation du cannabis sur le nombre de visites à l’urgence générale et elles montrent toutes une augmentation du nombre de visites associées au cannabis. Cela dit, ces résultats sont simplement observationnels et sont à mettre en perspective avec les tendances qui prévalaient déjà avant la légalisation du cannabis.

Conclusion Cette recension des écrits montre qu’il existe un nombre limité d’études concernant l’impact de la légalisation du cannabis récréatif sur les troubles en santé mentale. Il serait donc intéressant de poursuivre les recherches sur ce sujet.

Perceived Importance of Factors in Cannabis Purchase Decisions: A Best-worst Scaling Experiment

BACKGROUND

Consumers' access to cannabis has been considerably expanded in US states where recreational cannabis was legalized and commercialized. However, little is known about the important factors influencing consumers' purchase decisions in cannabis retail dispensaries. This study examined cannabis users' perceptions of the relative importance of policy-relevant factors when they made cannabis purchase decisions.

METHODS

An online survey was administered to 817 adult cannabis users in seven states in the US (California, Colorado, Maine, Massachusetts, Nevada, Oregon, and Washington) that had approved cannabis commercialization by the time of interview in January 2018. Twenty policy-relevant cannabis attributes were evaluated, including those pertaining to product characteristics, quality, package characteristics, price and free sample, store characteristics, and restrictions on use. A best-worst scaling experiment was employed, which asked respondents to select the most and the least important attributes in a choice scenario. Each respondent answered 10 choice scenarios, each including a random combination of four attributes out of the 20. The relative importance of each attribute was evaluated using hierarchical Bayesian estimation of mixed logit models.

RESULTS

Overall, 'quality', 'strain type', 'price', 'THC' (tetrahydrocannabinol) and 'pesticide' were the top five important attributes affecting cannabis users' willingness to buy cannabis in a dispensary. These five attributes jointly accounted for approximately half of the total importance. In subsample analysis, both recreational and dual-purpose users attached higher importance to 'quality', 'THC', and 'price', whereas medical users tended to think 'CBD' (cannabidiol) and 'pesticide' were more important. All cannabis users perceived 'package' to be the least important attribute. Gender had no major differences in perceptions.

CONCLUSIONS

Cannabis users in general perceived product characteristics, quality, and price to be important factors in their willingness to buy cannabis in dispensaries. There were heterogeneities in the perceptions by cannabis use purposes. The findings might deserve consideration in cannabis policy design.

Evaluation of Availability of Survey Data About Cannabis Use

IMPORTANCE

In response to increasing public support for cannabis legalization, understanding associations of state and federal policy changes related to cannabis legalization with patterns of cannabis use is important. A challenge for public health monitoring and research is significant variation in data availability related to cannabis use behaviors and perceptions across and within states and over time, including the availability of prelegalization vs postlegalization data.

OBJECTIVE

To review data available on cannabis use and related behaviors over time in Massachusetts and the US.

DESIGN, SETTING, AND PARTICIPANTS

This case series examined state and national surveys on public health and related behaviors and outcomes to review availability of cannabis-related data for Massachusetts for 8 key indicators over time. Additionally, the Behavioral Risk Factor Surveillance System (BRFSS) and Youth Risk Behavior Surveillance System for all states were reviewed. The analysis was conducted between February 1, 2019, and March 18, 2020.

EXPOSURES

Surveys that enable state-level estimation of cannabis use and related behaviors.

MAIN OUTCOMES AND MEASURES

Eight key indicators related to cannabis use behaviors and perceptions: lifetime cannabis use, age of initiation, frequency of use, location of use, method of use, source of cannabis, perceptions of cannabis, and reason for use (ie, medical vs nonmedical).

RESULTS

There were 7 surveys that monitored cannabis use and related behaviors in Massachusetts for adolescents and adults. No surveys monitored all 8 indicators of interest, and availability over time was limited. In the most recent BRFSS, 24 states asked cannabis-related questions, meaning BRFSS data on cannabis use was lacking for more than half of the US adult population. In the Youth Risk Behavior Surveillance System, 36 states asked standard cannabis questions; most other states had at least 1 question related to cannabis use and frequency.

CONCLUSIONS AND RELEVANCE

These findings of limitations of existing surveys, and particularly the lack of national questions in the BRFSS and Youth Risk Behavior Surveillance System, suggest that available data have substantial limitations for monitoring cannabis use. As cannabis policy changes continue, there is a need to remain focused on the availability of high-quality data sources that allow for critical public health research.

Marijuana use trends among college students in states with and without legalization of recreational use: initial and longer-term changes from 2008 to 2018

BACKGROUND AND AIMS

Young adult college students in the United States are likely to be affected by marijuana liberalization trends. However, changes in students' marijuana use following recreational marijuana legalization (RML) have not been examined in more than one RML state at a time, or beyond 1-2 years post-legalization.

DESIGN

Cross-sectional National College Health Assessment survey administered twice yearly from 2008 to 2018.

SETTING

A total of 587 4-year colleges and universities in 48 US states.

PARTICIPANTS

Undergraduates aged 18-26 years attending college in US states that did (n = 234 669 in seven states) or did not (n = 599 605 in 41 states) enact RML between 2008 and 2018.

MEASUREMENTS

Self-reported marijuana use (past 30 days) and individual and contextual covariates, institution-provided institutional and community covariates and publicly available dates when states enacted RML.

FINDINGS

Adjusting for covariates, state differences and state-specific linear time trends (accounting for pre-RML trends), prevalence of 30-day marijuana use increased more among students exposed to RML [odds ratio (OR) = 1.23, 95% confidence interval (CI) = 1.19-1.28, P < 0.001] than among non-RML state students throughout the same time-period; the results were similar for frequent use (≥ 20 days) (OR = 1.18, 95% CI = 1.10-1.27, P < 0.001). Interaction models supported stronger RML effects among students who were female, residing off-campus and aged 21 years and older; sexual orientation did not moderate RML effects. In the earliest states to enact RML (2012) there were increases in use prevalence in the second through the sixth year post-RML compared to pre-RML. In the second legalization group (2015) there were increases in the first and second year post-RML, and greater increases in the third year. In the later states (2016-17), increases were observed in both years after RML.

CONCLUSIONS

In US states that enacted recreational marijuana legislation from 2012 to 2017 there was evidence for a general trend towards greater increases in marijuana use by college students and differential impact by gender, legal using age and campus residence.

Assessing the public health impacts of legalizing recreational cannabis use: the US experience

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 can-nabis use that minimize adverse effects on public health.

The impact of cannabis legalization in Uruguay on adolescent cannabis use

BACKGROUND

In 2013, Uruguay became the first country in the world to legalize recreational cannabis, instituting a non-commercial state regulatory model of production and supply. This study provides the first empirical evidence on its impacts on adolescent use of cannabis and related risks.

METHODS

We use a generalization of the synthetic control method (SCM) to estimate the impact of legalization in Uruguay on adolescent past year and month cannabis use, perceived availability of cannabis and perceived risk of cannabis use. We compare biennial high school student self-reported survey data from Montevideo and regions in the interior of Uruguay post-legalization (2014-2018) and post initial implementation (2015-2018) to a synthetic counterfactual constructed using a weighted combination of 15 control regions in Chile.

RESULTS

We find no evidence of an impact on cannabis use or the perceived risk of use. We find an increase in student perception of cannabis availability (58% observed vs. 51% synthetic control) following legalization.

CONCLUSION

Our findings provide some support for the thesis that Uruguay's state regulatory approach to cannabis supply may minimize the impact of legalization on adolescent cannabis use. At the same time, our study period represents a period of transition: pharmacy access, by far the most popular means of access, was not available until the summer of 2017. Additional study will be important to assess the longer-term impacts of the fully implemented legalization regime on substance use outcomes.

Marijuana Legalization and Youth

Various states have legalized marijuana for medical purposes and/or decriminalized recreational marijuana use. These changes coincide with a decrease in perceived harmfulness of the drug and an increase in its use among youth. This change is of critical concern because of the potential harmful impact of marijuana exposure on adolescents. Marijuana use has been associated with several adverse mental health outcomes, including increased incidence of addiction and comorbid substance use, suicidality, and new-onset psychosis. Negative impacts on cognition and academic performance have also been observed. As the trend toward legalization continues, the pediatric community will be called on to navigate the subsequent challenges that arise with changing policies. Pediatricians are uniquely positioned to provide innovative care and educate youth and families on the ever-evolving issues pertaining to the impact of marijuana legalization on communities. In this article, we present and analyze the most up-to-date data on the effects of legalization on adolescent marijuana use, the effects of adolescent use on mental health and cognitive outcomes, and the current interventions being recommended for use in pediatric office settings.

Adolescent treatment admissions for marijuana following recreational legalization in Colorado and Washington

INTRODUCTION

There is concern that recreational marijuana legalization (RML) may lead to increased cannabis use disorder (CUD) among youth due to increased marijuana use. This study investigates whether adolescent substance use disorder treatment admissions for marijuana use increased in Colorado and Washington following RML.

METHODS

Annual data on 2008-2017 treatment admissions for marijuana use from the SAMHSA TEDS-A dataset for adolescents age 12-17 were used to model state treatment admissions trends. Difference-in-differences models were used to investigate whether treatment admissions increased following RML in Colorado/Washington compared to non-RML states, after adjusting for socioeconomic characteristics and treatment availability.

RESULTS

Over all states in the analysis, the rate of adolescent treatment admissions for marijuana use declined significantly over the study period (β=-3.375, 95 % CI=-4.842, -1.907), with the mean rate falling nearly in half. The decline in admissions rate was greater in Colorado and Washington compared to non-RML states following RML, though this difference was not significant (β=-7.671, 95 % CI=-38.798, 23.456).

CONCLUSION

Adolescent treatment admissions for marijuana use did not increase in Colorado and Washington following RML. This may be because youth marijuana use did not increase, CUD did not increase (even if use did increase), or treatment seeking behaviors changed due to shifts in attitudes and perceptions of risk towards marijuana use.

Psychiatric symptoms caused by cannabis constituents: a systematic review and meta-analysis

BACKGROUND

Approximately 188 million people use cannabis yearly worldwide, and it has recently been legalised in 11 US states, Canada, and Uruguay for recreational use. The potential for increased cannabis use highlights the need to better understand its risks, including the acute induction of psychotic and other psychiatric symptoms. We aimed to investigate the effect of the cannabis constituent Δ9-tetrahydrocannabinol (THC) alone and in combination with cannabidiol (CBD) compared with placebo on psychiatric symptoms in healthy people.

METHODS

In this systematic review and meta-analysis, we searched MEDLINE, Embase, and PsycINFO for studies published in English between database inception and May 21, 2019, with a within-person, crossover design. Inclusion criteria were studies reporting symptoms using psychiatric scales (the Brief Psychiatric Rating Scale [BPRS] and the Positive and Negative Syndrome Scale [PANSS]) following the acute administration of intravenous, oral, or nasal THC, CBD, and placebo in healthy participants, and presenting data that allowed calculation of standardised mean change (SMC) scores for positive (including delusions and hallucinations), negative (such as blunted affect and amotivation), and general (including depression and anxiety) symptoms. We did a random-effects meta-analysis to assess the main outcomes of the effect sizes for total, positive, and negative PANSS and BPRS scores measured in healthy participants following THC administration versus placebo. Because the number of studies to do a meta-analysis on CBD's moderating effects was insufficient, this outcome was only systematically reviewed. This study is registered with PROSPERO, CRD42019136674.

FINDINGS

15 eligible studies involving the acute administration of THC and four studies on CBD plus THC administration were identified. Compared with placebo, THC significantly increased total symptom severity with a large effect size (assessed in nine studies, with ten independent samples, involving 196 participants: SMC 1·10 [95% CI 0·92-1·28], p<0·0001); positive symptom severity (assessed in 14 studies, with 15 independent samples, involving 324 participants: SMC 0·91 [95% CI 0·68-1·14], p<0·0001); and negative symptom severity with a large effect size (assessed in 12 studies, with 13 independent samples, involving 267 participants: SMC 0·78 [95% CI 0·59-0·97], p<0·0001). In the systematic review, of the four studies evaluating CBD's effects on THC-induced symptoms, only one identified a significant reduction in symptoms.

INTERPRETATION

A single THC administration induces psychotic, negative, and other psychiatric symptoms with large effect sizes. There is no consistent evidence that CBD induces symptoms or moderates the effects of THC. These findings highlight the potential risks associated with the use of cannabis and other cannabinoids that contain THC for recreational or therapeutic purposes.

FUNDING

UK Medical Research Council, Maudsley Charity, Brain and Behavior Research Foundation, Wellcome Trust, and the UK National Institute for Health Research.