Does liberalisation of cannabis policy influence levels of use in adolescents and young adults? A systematic review and meta-analysis

Trends in youth cannabis use across cannabis legalization: Data from the COMPASS prospective cohort study

Canada legalized recreational cannabis use for adults on October 17, 2018 with decision-makers emphasising the need to reduce cannabis use among youth. We sought to characterise trends of youth cannabis use before and after cannabis legalization by relying on a quasi-experimental design evaluating cannabis use among high school students in Alberta, British Columbia, Ontario, and Québec who participated in the COMPASS prospective cohort study. Overall trends in use were examined using a large repeat cross-sectional sample (n = 102,685) at two time points before legalization (16/17 and 17/18 school years) and one after (18/19 school year). Further differential changes in use among students affected by legalization were examined using three sequential four-year longitudinal cohorts (n = 5,400) of students as they progressed through high school. Youth cannabis use remains common with ever-use increasing from 30.5% in 2016/17 to 32.4% in 2018/19. In the repeat cross-sectional sample, the odds of ever use in the year following legalization were 1.05 times those of the preceding year (p = 0.0090). In the longitudinal sample, no significant differences in trends of cannabis use over time were found between cohorts for any of the three use frequency metrics. Therefore, it appears that cannabis legalization has not yet been followed by pronounced changes on youth cannabis use. High prevalence of youth cannabis use in this sample remains a concern. These data suggest that the Cannabis Act has not yet led to the reduction in youth cannabis use envisioned in its public health approach.

Public health impacts to date of the legalisation of medical and recreational cannabis use in the USA

The legality of cannabis use has been changing in a number of jurisdictions around the world. In the U.S., it has been legalised for medicinal and/or recreational uses in 34 jurisdictions and counting. This study leverages the decades-long experience of legalisation in the U.S. to provide an overview of the associated changes in public attitudes, cannabis markets and adverse health effects. We found a broad-based warming of public attitudes toward legalisation, potentially influenced by the increasingly positive portrayal of cannabis in media and declines in cannabis risk perceptions. Potency of cannabis products increased significantly while prices fell sharply. Although adults were less responsive to price changes than adolescents, adults who use cannabis regularly were sensitive to prices, with an estimated 10% price reduction leading to about 2.5% increase in the rate of use. Overall, past-year cannabis use has increased in adults since 2002, and adults over 26 years old who resided in states with medicinal cannabis laws were more likely to have used cannabis in the past 30 days, to have used daily, and to have higher rates of cannabis use disorders than adults who resided in states without legalised medicinal cannabis. Traffic fatalities involving cannabis temporarily increased in some states post-legalisation, and there were more presentations to medical services related to chronic regular cannabis use. There is suggestive evidence that adverse health consequences have increased among people who use cannabis regularly since legalisation. More robust research is needed to determine whether these effects of legalisation are temporary or long-term.

Cannabis Policy Changes and Adolescent Cannabis Use: Evidence from Europe

Cannabis accounts for the largest share of the illicit drug market, with a high prevalence of use even among adolescents. To tackle this longstanding problem, many kinds of reforms to national cannabis control policies have been implemented in Europe, but their effectiveness is still unclear. This paper analyses the association between selected categories of cannabis policy reforms and changes in perceived cannabis availability and patterns of use among adolescents. Data from 20 European countries across 15 years were drawn from a novel database of the European school Survey Project on Alcohol and other Drugs (ESPAD). Our analysis is based on a Difference-in-Differences design, which application is allowed by the fact that only thirteen out of the twenty countries included implemented policy changes. The results suggest that selected categories of reforms influence the availability and prevalence of cannabis use. In particular, some forms of restrictive intervention reduce the general prevalence of use and more liberal reforms seem linked to an increase in the share of students initiating use of cannabis. We find no evidence of an effect of policy changes on the share of frequent users, which are presumably those more likely to develop use-related health consequences.

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.

Prevalence and modes of cannabis use among youth in Canada, England, and the US, 2017 to 2019

OBJECTIVE

Cannabis markets are evolving in terms of greater diversity and potency of products. The current study examined changes in cannabis use and modes of consumption among 16- to 19-year-olds in three markets with different regulatory frameworks: England, Canada, and the United States (US).

METHODS

Repeat cross-sectional online surveys were conducted in 2017, 2018, and 2019, with samples of 16- to 19-year-olds recruited from commercial panels in Canada (n = 11,779), England (n = 11,117), and the US (n = 11,869). Regression models examined changes in the prevalence of any cannabis use and use of seven modes of consumption, across the countries.

RESULTS

Cannabis use among youth was more prevalent among respondents in Canada and the US than in England in all years and increased to a greater extent between 2017 and 2019 (p < .001 for all contrasts). Among past 30-day cannabis consumers, the prevalence of vaping oils/liquids and the use of cannabis extracts (oil, wax and shatter) increased in all countries, and was significantly higher in Canada and US. For example, the prevalence of vaping oils/liquids increased from 24.2 % in 2017 to 52.1 % in 2019 among past 30-day cannabis consumers in the US (AOR = 3.46, 95 %CI = 2.57-4.66).

CONCLUSION

Prevalence is increasing for the most potent categories of cannabis products, particularly among youth in Canada and the US. Future research should examine the potential risks of these products and whether shifts in modes of cannabis reflect recent permissive changes to cannabis policy.

Pain Profiles among Young Adult Cannabis Users: An Analysis of Antecedent Factors and Distal Outcomes

BACKGROUND

Pain is a primary reason for medical cannabis use among young adults, however little is known about the patterns of pain in this group. This study identified pain profiles among young adult cannabis users and examined related antecedents and distal outcomes.

METHODS

Past 30-day cannabis users aged 18-26, both medical cannabis patients and non-patients, were enrolled in Los Angeles in 2014-2015. A latent class analysis was used to identify pain classes based on history of chronic pain conditions and recent non-minor pain. The study assessed the predictors of membership in pain classes and examined the association of classes with recent mental health characteristics, cannabis use motives and practices.

RESULTS

Three classes were identified: Low pain (56.3%), Multiple pain (27.3%), and Nonspecific pain (16.4%). In adjusted models, lifetime insomnia was associated with membership in Multiple pain and Nonspecific pain classes versus the Low pain class. Medical cannabis patients and Hispanics/Latinos were more likely to belong to the Multiple pain class than the other classes. Regarding recent outcomes, the Multiple pain and Nonspecific pain classes were more likely than the Low pain class to use cannabis to relieve physical pain. Additionally, the Multiple pain class had a higher probability of psychological distress, self-reported medical cannabis use, consuming edibles, and using cannabis to sleep compared to one or both other classes.

CONCLUSION

Findings suggest that young adult cannabis users can be separated into distinct groups with different pain profiles. The Multiple pain profile was associated with medically-oriented cannabis use motives and practices.

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.

Facing the option for the legalisation of cannabis use and supply in New Zealand: An overview of relevant evidence, concepts and considerations

ISSUES

Non-medical cannabis policies are changing, including towards legalisation-with-regulation frameworks. New Zealand will hold a public referendum on cannabis legalisation in 2020. We reviewed data on cannabis use and health/social harms; policy reform options; experiences with and outcomes of reforms elsewhere; and other relevant considerations towards informing policy choices in the upcoming referendum.

APPROACH

Relevant epidemiological, health, social, criminal justice and policy studies and data were identified and comprehensively reviewed.

KEY FINDINGS

Cannabis use is common (including in New Zealand) and associated with risks for health and social harms, mainly concentrated in young users; key harms are attributable to criminalisation. 'Decriminalisation' reforms have produced ambivalent results. Existing cannabis legalisation frameworks vary considerably in main parameters. Legalisation offers some distinct advantages, for example regulated use, products and user education, yet outcomes depend on essential regulation parameters, including commercialisation, and policy ecologies. While major changes in use are not observed, legalisation experiences are inconclusive to date, including mixed health and social outcomes, with select harms increasing and resilient illegal markets. It is unclear whether legalisation reduces cannabis exposure or social harms (e.g. from enforcement) for youth.

IMPLICATIONS/CONCLUSIONS

No conclusive overall evidence on the outcomes of legalisation elsewhere exists, nor is evidence easily transferable to other settings. Legalisation offers direct social justice benefits for adults, yet overall public health impacts are uncertain. Legalisation may not categorically improve health or social outcomes for youth. Legalisation remains a well-intended, while experimental policy option towards more measured and sensible cannabis control and overall greater policy coherence, requiring close monitoring and possible adjustments depending on setting-specific outcomes.

Adolescent cannabis use, cognition, brain health and educational outcomes: A review of the evidence

We review the findings of systematic reviews and meta-analyses of case-control studies that examine brain functioning and cognitive correlates of adolescent cannabis use using structural and functional neuroimaging tools and standardised neuropsychological tests. We also examine prospective epidemiological studies on the possible effects of adolescent and young adult cannabis use on cognitive performance in adult life and the completion of secondary education. We summarize the findings of studies in each of these areas that have been published since the most recent systematic review. Systematic reviews find that adolescent cannabis use is inconsistently associated with alterations in the structure of prefrontal and temporal brain regions. Meta-analyses reveal functional alterations in the parietal cortex and putamen. Differences in the orbitofrontal cortex predate cannabis use; it is unclear if they are affected by continued cannabis use and prolonged abstinence. Longitudinal and twin studies report larger declines in IQ among cannabis users than their non-using peers but it is unclear whether these findings can be attributed to cannabis use or to genetic, mental health and environmental factors. Several longitudinal studies and a meta-analysis of cross-sectional studies suggest that there is some cognitive recovery after abstinence from cannabis. Longitudinal studies and some twin studies have found that cannabis users are less likely to complete secondary school than their non-using controls. This association might reflect an effect of cannabis use and/or the social environment of cannabis users and their cannabis using peers. Cognitive performance is altered in some domains (e.g. IQ, verbal learning) in young people while they are regularly using cannabis. There are two important messages to adolescents and young adults: First, cannabis has potentially detrimental effects on cognition, brain and educational outcomes that persist beyond acute intoxication. Second, impaired cognitive function in cannabis users appears to improve with sustained abstinence.

International differences in patterns of cannabis use among adult cigarette smokers: Findings from the 2018 ITC Four Country Smoking and Vaping Survey

BACKGROUND

Although evidence shows that co-use of cigarettes and cannabis is common, there is little research examining if co-use patterns vary depending on the regulatory environment for cannabis. This study examined patterns of co-use and perceptions of relative harm among cigarette smokers in four countries with different histories, and at different stages of cannabis legalization.

METHODS

Data are from the 2018 International Tobacco Control 4CV Survey and included 10035 adult cigarette smokers from Canada, United States (US), Australia, and England. At the time of the survey, Canada and the US had relatively more permissive cannabis regulations compared to Australia and England.

RESULTS

Among this sample of 10035 cigarette smokers, Canada had the highest rate of cannabis co-use in the last 12 months (36.3%), followed by the US (29.1%), England (21.6%), and Australia (21.4%). Among past 12 month co-users (n = 3134), the US (40.2%) and Canada (35.2%) had the highest rates of daily cannabis use, followed by smokers in England (26.3%) and Australia (21.7%); Australian co-users had the highest rate of infrequent (

CONCLUSION

Patterns of tobacco and cannabis co-use differed between countries. Smokers in Canada and the US had higher rates of co-use, daily cannabis use, dual-daily use of both cannabis and cigarettes, and were more likely to perceive smoked cannabis as less harmful than cigarettes compared to England and Australia. Further attention as to how varying cannabis regulations may impact co-use patterns is warranted.

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Key Words

• Cannabis
• Co-use
• Harm Perceptions
• Policy
• Regulation
• Tobacco cigarettes

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MESH Headings Collapse

Grants

• P01 CA200512 NCI NIH HHS

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Affiliation(s)

Shannon Gravely Department of Psychology, University of Waterloo, Waterloo, Canada.
Pete Driezen Department of Psychology, University of Waterloo, Waterloo, Canada; School of Public Health and Health Systems, University of Waterloo, Waterloo, Canada
Danielle M Smith Department of Health Behavior, Roswell Park Comprehensive Cancer Center, Buffalo, United States
Ron Borland School of Psychological Sciences, University of Melbourne, Melbourne, VIC, Australia; Cancer Council Victoria, Melbourne, VIC, Australia
Eric N Lindblom O'Neill Institute for National & Global Health Law, Georgetown University Law Center, Washington, DC United States
David Hammond School of Public Health and Health Systems, University of Waterloo, Waterloo, Canada
Ann McNeill King's College London, Addictions Department, Institute of Psychiatry, Psychology & Neuroscience, London, United Kingdom; UK Centre for Tobacco & Alcohol Studies, Nottingham, United Kingdom
Andrew Hyland Department of Health Behavior, Roswell Park Comprehensive Cancer Center, Buffalo, United States
K Michael Cummings Department of Psychiatry & Behavioral Sciences, Medical University of South Carolina, Charleston, United States; Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, United States
Gary Chan Centre for Youth Substance Abuse Research, The University of Queensland, Brisbane, QLD, Australia
Mary E Thompson Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Canada
Christian Boudreau Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Canada
Nadia Martin Department of Psychology, University of Waterloo, Waterloo, Canada
Janine Ouimet Department of Psychology, University of Waterloo, Waterloo, Canada
Ruth Loewen Department of Psychology, University of Waterloo, Waterloo, Canada
Anne C K Quah Department of Psychology, University of Waterloo, Waterloo, Canada
Maciej L Goniewicz Department of Health Behavior, Roswell Park Comprehensive Cancer Center, Buffalo, United States
James F Thrasher Department of Health Promotion, Education & Behavior, Arnold School of Public Health, University of South Carolina, Columbia, United States; Tobacco Research Department, Center for Population Health Research, National Institute of Public Health, Cuernavaca, Mexico
Geoffrey T Fong Department of Psychology, University of Waterloo, Waterloo, Canada; School of Public Health and Health Systems, University of Waterloo, Waterloo, Canada; Ontario Institute for Cancer Research, Toronto, Canada

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Extension of the Theory of Planned Behavior (TPB) to Predict Patterns of Marijuana Use among Young Iranian Adults

Background: Marijuana use is increasing among adolescents and young adults. Long-term marijuana use magnifies the risk of a wide variety of behavioral, cognitive-emotional, and neurological problems, and can be a gateway to use of other drugs. In the present study, we investigated the cognitive-emotional and behavioral predictors of marijuana use. To this end, young Iranian adults answered questions based on an extended Theory of Planned Behavior (TPB) and related it to marijuana use. We hypothesized that cognitive-emotional and behavioral factors would predict intention to use marijuana, and that this, in turn, would predict actual consumption. Methods: A total of 166 young Iranian adults (mean age: 20.51 years; 15.7% females) attending a walk-in center for drug use took part in this cross-sectional study. Participants completed questionnaires covering sociodemographic information, frequency of marijuana use per week, along with questionnaires assessing the following dimensions of the TPB: attitude towards marijuana use, subjective norms, self-efficacy to resist marijuana use, environmental constraints, problem-solving skills, and behavioral intention for marijuana use. Results: Mean marijuana use was found to be 4.6 times/week. Attitude towards marijuana use, subjective norms, environmental constraints, and behavioral intention to use marijuana were positively correlated to each other and with marijuana use/week. In contrast, higher self-efficacy and problem-solving skills were associated with lower marijuana use/week. The multiple regression analysis showed that a positive attitude to marijuana use, lower self-efficacy in resisting its use, higher behavioral intention, and poorer problem-solving skills predicted actual use. Conclusion: The pattern of results suggests that dimensions of TPB can explain marijuana use among young Iranian adults self-admitted to a walk-in center for drug use. Specifically, poor problem-solving skills, low self-efficacy in resisting marijuana use, and positive labelling of its use appeared to be the best predictors of actual use. It follows that prevention programs aimed at improving problem-solving skills and raising self-efficacy, along with educational interventions aimed at highlighting the negative effects of marijuana might decrease the risk of its use among young adults in Iran.

Violence and Cannabis Use: A Focused Review of a Forgotten Aspect in the Era of Liberalizing Cannabis

There has been a shift surrounding societal and legal perspectives on cannabis reflecting changing public attitudes towards the perceived safety and social acceptability of cannabis use. With cannabis liberalization internationally, the focus of most cannabis-related harms has been on effects with users themselves. Harm-to-others including injuries from violence have nevertheless been unfortunately largely overlooked. While studies remain heterogeneous, there is meta-analytical evidence pointing towards an association. The aims of this focused review are two-fold: (I) review the evidence from meta-analyses on the association between cannabis and violence; and (II) provide an overview of possible mechanisms relating cannabis use to violence. First, evidence from meta-analytical studies in youths, intimate partners, and individuals with severe mental disorders have shown that there is a global moderate association between cannabis use and violence, which is stronger in the latter more at-risk population. Preliminary data has even highlighted a potential dose-response relationship with larger effects in more frequent users. Although of importance, this subject has remained essentially forgotten as a public health concern. While literature remains inconclusive, data has suggested potential increases in cannabis use following liberalization policies. This may increase violent outcomes if the effect is directly related to the use of cannabis by means of its psychophysiological modifications. However, for the moment, the mechanisms associating cannabis use and violence remain to be clearly resolved. Considering the recency of policy changes on cannabis, further methodologically sound research using longitudinal designs should examine the effects that cannabis use may have on different forms of violence and the trends that emerge, while evaluating the effects of possible confounding factors (e.g. other substance use). In addition, as evidence-based research from meta-analyses have shown that cannabis use is associated with violence, measures must be taken to mitigate the risks.

Early evidence of the impact of cannabis legalization on cannabis use, cannabis use disorder, and the use of other substances: Findings from state policy evaluations

Background: The past decade has seen unprecedented shifts in the cannabis policy environment, and the public health impacts of these changes will hinge on how they affect patterns of cannabis use and the use and harms associated with other substances.Objectives: To review existing research on how state cannabis policy impacts substance use, emphasizing studies using methods for causal inference and highlighting gaps in our understanding of policy impacts on evolving cannabis markets.Methods: Narrative review of quasi-experimental studies for how medical cannabis laws (MCLs) and recreational cannabis laws (RCLs) affect cannabis use and use disorders, as well as the use of or harms from alcohol, opioids, and tobacco.Results: Research suggests MCLs increase adult but not adolescent cannabis use, and provisions of the laws associated with less regulated supply may increase adult cannabis use disorders. These laws may reduce some opioid-related harms, while their impacts on alcohol and tobacco use remain uncertain. Research on RCLs is just emerging, but findings suggest little impact on the prevalence of adolescent cannabis use, potential increases in college student use, and unknown effects on other substance use.Conclusions: Research on how MCLs influence cannabis use has advanced our understanding of the importance of heterogeneity in policies, populations, and market dynamics, but studies of how MCLs relate to other substance use often ignore these factors. Understanding effects of cannabis laws requires greater attention to differences in short- versus long-term effects of the laws, nuances of policies and patterns of consumption, and careful consideration of appropriate control groups.

Cannabis and youth protection in Colorado's commercial adult-use market: A qualitative investigation

INTRODUCTION

Arguments both for and against the legalization of cannabis often include the issue of youth protection. At the time of writing 5-years after the implementation of the Coloradan recreational cannabis market (CRCM), no statistically significant increase in consumption had been identified. This paper aimed to provide a thick descriptive account of youth prevention objectives stipulated in the pre-implementation phase of the CRCM and compare these with the real-world experience of regulators and other stakeholders involved with market implementation.

METHODOLOGY AND METHODS

A qualitative descriptive methodology was used that involved the following methods: document analysis, deductive coding, thematic analysis, and thick description. Two data sets relevant to youth protection in the context of a legal cannabis market in Colorado were examined. Data set 1 (DS1) examined government documents (n = 13) related to the pre-implementation phase from November 2012 - December 2013. Data set 2 (DS2) consisted of semi-structured face-to-face interviews conducted with key stakeholders (n = 32) in 2016 and 2017.

RESULTS

Five themes emerged including advertising restrictions (DS1), education (DS1), appropriation of funds (DS2), impact assessment (DS2), and evolving messages in prevention education campaigns (DS2).

DISCUSSION

Multiple lessons for other jurisdictions were highlighted in the study.