The Effect of Medical Marijuana Laws on Marijuana-Related Attitude and Perception Among US Adolescents and Young Adults

Adolescents' Cannabis Knowledge and Risk Perception: A Systematic Review

To systematically review evidence evaluating cannabis-related knowledge and perception of risk in children and adolescents. We systematically searched Medline, PsycINFO, and EMBASE using Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology. 133 studies from around the world (including ages 10-18 yrs) met inclusion criteria, with 70% meeting grade 2C quality. Increased knowledge and perception of risk of cannabis frequently correlated with lower levels of current use and intent to use. Studies examining correlations over time generally demonstrated increased adolescent cannabis use and decreased perception of risk. Included prevention-based interventions often enhanced knowledge and/or perception of risk in adolescents exposed to the intervention. Studies exploring outcomes relating to legislative changes for recreational marijuana use demonstrated considerable heterogeneity regarding knowledge and perception of risk whereas studies that focused on medicinal marijuana legislative changes overwhelmingly demonstrated a decrease in perception of risk post legalization. Increased knowledge and perception of risk of cannabis in adolescents often correlate with lower levels of current use and intention to use in the future. Further study and implementation of public health and clinically-oriented strategies that seek to increase knowledge among youth about the potential health harms of cannabis use should continue and be prioritized.

Young Adult Depression and Cannabis Use: Associations Before and After Recreational Legalization

INTRODUCTION

The co-occurrence of depression with cannabis use worsens both mood and substance use disorder outcomes, with young adults particularly at risk of co-occurrence. This research investigates whether the association of state-level prevalence rates of young adult (age 18-25) depression and cannabis use in the U.S. changed following enactment of recreational (adult use) cannabis legalization between 2008 and 2019.

METHODS

Annual, state prevalence data on past-year major depressive episode (hereafter, depression) and past-month cannabis use were extracted from the National Survey on Drug Use and Health (N=600 state-year observations). Moderated regression models tested whether the association of depression with cannabis use differed before versus after recreational legalization by comparing prevalence rates of depression and cannabis use in states that enacted recreational legalization to those that did not, while fixing state, year, and medical legalization effects. Data were accessed and analyzed in 2023.

RESULTS

Prevalence rates of both depression and cannabis use increased throughout the study period. The positive statistical effect of depression on cannabis use more than doubled in magnitude after legalization (β=0.564, 95% CI=0.291, 0.838) as compared to before (β=0.229, 95% CI=0.049, 0.409), representing a significant change (β=0.335, 95% CI=0.093, 0.577).

CONCLUSIONS

These results suggest that the association between prevalence rates of young adult depression and cannabis use strengthened following recreational legalization in the U.S. This is potentially due to increases in cannabis accessibility and the acceptance of the health benefits of cannabis, which may enhance the use of cannabis as a coping mechanism among young adults with depression.

The effect of marijuana use in adolescence on college and graduate degree attainment

We estimate the long-term effect of using marijuana in adolescence on college and graduate degree attainment measured approximately 20 years later. We rely on the first two waves (1994-1996) and the fifth wave (2016-2018) of the National Longitudinal Study of Adolescent to Adult Health and estimate instrumental variables models that exploit the network structure at the second degree by using marijuana use status of friends of friends who are not themselves friends of the respondent in order to instrument for the respondent's marijuana use. Our models also include school and grade fixed effects. Marijuana use in adolescence leads to a large reduction in the likelihood of college and graduate degree attainment by the time respondents are aged 33-43 years old.

Past Cannabis Use, Health-Related Worry, and Beliefs About Perceived Benefits of Cannabis Among American Indians/Alaska Natives

BACKGROUND

Most adults report beliefs that cannabis has at least one benefit (e.g., stress relief, chronic pain management); however, the benefits are not well established. Beliefs about cannabis benefits are associated with the initiation of use, whereas beliefs about the risks of cannabis are protective factors against its use. Little is known about how health-related beliefs impact cannabis use among American Indians/Alaska Natives (AIAN).

PURPOSE

This exploratory study examined beliefs about perceived benefits (i.e., stress relief, pain management) of cannabis, how beliefs vary as a function of use, and associations between health worry and benefits of cannabis among AIAN adults.

METHODS

Participants (n = 182) were on average 41.4 (SD = 16.3) years old, 63.9% female, and identified as AIAN. Participants were asked questions about general demographics, health-related worry and perceptions, and cannabis use. Linear regressions were conducted to examine associations.

RESULTS

Those who used cannabis in the past year were more likely to agree that cannabis relieves stress and less likely to believe that those who use cannabis should be very worried about their health. Participants who agreed that those who use cannabis should be worried about their health were less likely to report beliefs that cannabis relieves stress or helps with chronic pain.

CONCLUSIONS

Our study confirms the role of health-related perceptions and worry about cannabis products with cannabis use among this population that may be at risk for higher cannabis use. Findings may have implications for cannabis policy at the tribal, state, and federal levels and the need for the development of targeted communications about the true health risks of cannabis.

Health, safety, and socioeconomic impacts of cannabis liberalization laws: An evidence and gap map

Background

Globally, cannabis laws and regulations are rapidly changing. Countries are increasingly permitting access to cannabis under various decriminalization, medicalization, and legalization laws. With strong economic, public health, and social justice incentives driving these domestic cannabis policy reforms, liberalization trends are bound to continue. However, despite a large and growing body of interdisciplinary research addressing the policy-relevant health, safety, and socioeconomic consequences of cannabis liberalization, there is a lack of robust primary and systematic research that comprehensively investigates the consequences of these reforms.

Objectives

This evidence and gap map (EGM) summarizes the empirical evidence on cannabis liberalization policies. Primary objectives were to develop a conceptual framework linking cannabis liberalization policies to relevant outcomes, descriptively summarize the empirical evidence, and identify areas of evidence concentration and gaps.

Search Methods

We comprehensively searched for eligible English-language empirical studies published across 23 academic databases and 11 gray literature sources through August 2020. Additions to the pool of potentially eligible studies from supplemental sources were made through November 2020.

Selection Criteria

The conceptual framework for this EGM draws upon a legal epidemiological perspective highlighting the causal effects of law and policy on population-level outcomes. Eligible interventions include policies that create or expand access to a legal or decriminalized supply of cannabis: comprehensive medical cannabis laws (MCLs), limited medical cannabidiol laws (CBDLs), recreational cannabis laws (RCLs), industrial hemp laws (IHLs), and decriminalization of cultivations laws (DCLs). Eligible outcomes include intermediate responses (i.e., attitudes/behaviors and markets/environments) and longer-term consequences (health, safety, and socioeconomic outcomes) of these laws.

Data Collection and Analysis

Both dual screening and dual data extraction were performed with third person deconfliction. Primary studies were appraised using the Maryland Scientific Methods Scale and systematic reviews were assessed using AMSTAR 2.

Main Results

The EGM includes 447 studies, comprising 438 primary studies and nine systematic reviews. Most research derives from the United States, with little research from other countries. By far, most cannabis liberalization research focuses on the effects of MCLs and RCLs. Studies targeting other laws-including CBDLs, IHLs, and DCLs-are relatively rare. Of the 113 distinct outcomes we documented, cannabis use was the single most frequently investigated. More than half these outcomes were addressed by three or fewer studies, highlighting substantial evidence gaps in the literature. The systematic evidence base is relatively small, comprising just seven completed reviews on cannabis use (3), opioid-related harms (3), and alcohol-related outcomes (1). Moreover, we have limited confidence in the reviews, as five were appraised as minimal quality and two as low quality.

Authors’ Conclusions

More primary and systematic research is needed to better understand the effects of cannabis liberalization laws on longer-term-and arguably more salient-health, safety, and socioeconomic outcomes. Since most research concerns MCLs and RCLs, there is a critical need for research on the societal impacts of industrial hemp production, medical CBD products, and decriminalized cannabis cultivation. Future research should also prioritize understanding the heterogeneous effects of these laws given differences in specific provisions and implementation across jurisdictions.

Consequences of adolescent drug use

Substance use in adolescence is a known risk factor for the development of neuropsychiatric and substance use disorders in adulthood. This is in part due to the fact that critical aspects of brain development occur during adolescence, which can be altered by drug use. Despite concerted efforts to educate youth about the potential negative consequences of substance use, initiation remains common amongst adolescents world-wide. Additionally, though there has been substantial research on the topic, many questions remain about the predictors and the consequences of adolescent drug use. In the following review, we will highlight some of the most recent literature on the neurobiological and behavioral effects of adolescent drug use in rodents, non-human primates, and humans, with a specific focus on alcohol, cannabis, nicotine, and the interactions between these substances. Overall, consumption of these substances during adolescence can produce long-lasting changes across a variety of structures and networks which can have enduring effects on behavior, emotion, and cognition.

Population-based examination of substance use disorders and treatment use among US young adults in the National Survey on Drug Use and Health, 2011-2019

Background

Compared with adults of other age groups, young adults are more likely to have substance use disorders (SUDs) but less likely to receive treatment. Untreated SUDs can lead to lethal consequences, particularly deaths related to drug overdose.

Objectives

This study aimed to examine trends and sociodemographic differences in the prevalence and treatment use of SUDs among US young adults aged 18 to 25 in the National Survey on Drug Use and Health 2011-2019.

Methods

Bivariable logistic regression analyses were conducted to examine annual changes in the prevalence and treatment use of SUDs, and multivariable logistic regression was used to examine sociodemographic differences in SUD prevalence and treatment use in the pooled sample of young adults from 2011 to 2019.

Results

From 2011 to 2019, the overall SUD prevalence increased significantly from 5.4% to 6.2%. Cannabis use disorder was the most common SUD annually. Groups with lower prevalence of SUDs included females, young adults aged 22-25, and Hispanic, Black, and Asian participants. Across the survey years, the prevalence of treatment use fluctuated insignificantly between 10.9% and 16.9% among young adults with SUDs, and most young adults received SUD treatment in self-help groups and residential and outpatient rehabilitation facilities. Compared to White participants, treatment use was lower in Hispanic, Black, Asian participants, as well as young adults of two or more races. Young adults covered by Medicaid/CHIP were more likely to use treatment.

Conclusions

This study revealed an alarming level of unmet treatment need and significant disparities in treatment use among young adults with SUDs. To reduce barriers to treatment utilization, more coordinated efforts that leverage policy and structural changes alongside innovations to engage young adults with SUD care are needed.

Student perceptions of cannabis use

OBJECTIVE

This qualitative study explored post-secondary students' perceptions of cannabis use on students' health, academic pursuits, and social lives, and investigated how these issues have been impacted by the legalization of recreational cannabis.

Participants: 20 undergraduate students at a small liberal arts university in Atlantic Canada participated in this study.

Methods: Semi-structured interviews were used to learn more about student perceptions of cannabis. Interview transcripts were analyzed using general thematic analysis.

Results: Students in this study report using cannabis in thoughtful ways, balancing various considerations in terms of health, social connections, and academics. They were aware that cannabis is not a risk-free drug and took some steps to manage risks.

Conclusion: Knowing why young adults believe they use cannabis is information for university professionals who want to develop effective harm reduction campaigns.

Recreational cannabis legalization alters associations among cannabis use, perception of risk, and cannabis use disorder treatment for adolescents and young adults

OBJECTIVE

Understanding how recreational cannabis legalization may impact cannabis use disorder (CUD) among adolescents and young adults is key to developing an appropriate public health response. This research investigates whether associations among adolescent and young adult perception of risk of harm from cannabis use, prevalence of past-month cannabis use, and rate of CUD treatment admissions changed following recreational cannabis legalization in the US, 2008-2019.

METHODS

Data from the NSDUH and TEDS-A datasets are employed in difference-in-differences models of the effect of recreational legalization on perception of risk, cannabis use prevalence, and CUD treatment admissions. Moderated models test whether associations among variables changed following recreational legalization.

RESULTS

Following recreational legalization: 1) adolescent and young adult past-month cannabis use prevalence increased; 2) among both adolescents and young adults, the association of lower perception of risk of harm with higher cannabis use prevalence was strengthened; 3) among adolescents, the association of higher cannabis use prevalence with higher CUD treatment admissions was suppressed; and 4) among young adults, an association of higher cannabis use prevalence with lower CUD treatment admissions emerged.

CONCLUSIONS

Recreational legalization is likely to increase cannabis use among adolescents and young adults who perceive cannabis as less harmful, while at the same time reduce rates of CUD treatment utilization. These trends portend an increase in unmet need for CUD treatment for age groups particularly vulnerable to the development and negative consequences of CUD.

The kids aren't alright: The effects of medical marijuana market size on adolescents

We exploit shocks to US federal enforcement policy to assess how legal medical marijuana market size affects youth marijuana use and consequences for youth traffic-related fatalities. Using hand-collected data on state medical marijuana patient rates to develop a novel measure of market size, we find that legal market growth increases youth marijuana use. Likely mechanisms are lower prices and easier access. Youth die more frequently from alcohol-involved car accidents, suggesting complementarities for youths. The consequences of marijuana legalization for youth are not immediate, but depend on how supply-side regulations affect production and prices.

The influence of parent and peer disapproval on youth marijuana use mediated by youth risk perception: Focusing on the state comparison

BACKGROUND

The prevention of youth marijuana use has become a national priority in the United States. This study examined the influence of parent and peer disapproval on youth marijuana use, mediated by youth risk perception. Because the legal status of marijuana use can influence individual perceptions of the drug, this study investigated differences in the mediating mechanism between youth living in states with medical marijuana legalization (MML) and those living in non-MML states.

METHODS

The 2019 National Survey of Drug Use and Health was used with a youth population aged 12-17 years (N = 2293). Structural equation modeling and bias-corrected bootstrapping were used to examine hypothesized path models and to evaluate the mediating effect of youth risk perception.

RESULT

Findings demonstrated that parent and peer disapproval significantly increased youth risk perception of marijuana and reduced youth marijuana use. Second, youth risk perception significantly mediated the association between parent and peer disapproval and youth marijuana use. Third, parent disapproval had a more significant direct effect on youth marijuana use, while peer disapproval had a more significant indirect effect on youth marijuana use via youth risk perception. Finally, the results showed a similar pattern in the mechanism between youths living in MML states compared with those in non-MML states in terms of significance and direction.

CONCLUSION

The findings suggested a need for improvements in marijuana related policies for both MML and non-MML states. Moreover, parent and peer focused strategies for education and prevention concerning marijuana use among youth are emphasized.

Substance-Specific Risk Factors among Young Adults: Potential Prevention Targets across Cannabis-Permissive Environments

PURPOSE

This study examined levels of substance-specific risk factors such as perception of harm from substance use among young adults in a range of cannabis-permissive environments. The main objective was to inform future preventive interventions aimed at reducing cannabis use in the context of increasingly permissive environments.

METHODS

Data came from the Community Youth Development Study (CYDS) collected in 2016 when participants were about 23 years old (n = 1,722 participants residing in 46 U.S. states). Young adults self-reported their perceptions about the harms related to cannabis, alcohol, and cigarette use; attitudes about and ease of access to cannabis and other substances; and perceived wrongfulness and social acceptability of cannabis, alcohol, and cigarette use and of selling of cannabis and other illegal drugs.

RESULTS

Young adults in more permissive cannabis contexts reported higher levels of all cannabis-specific risk factors (e.g., greater access to and more favorable attitudes about cannabis use), except for perception of harm from regular cannabis use. However, permissiveness of the cannabis environment was not associated with heightened levels of risk factors for other substance use (such as alcohol, cigarettes, and opioids).

CONCLUSIONS

Future preventive interventions for young adults living in more permissive cannabis contexts may need to focus on cannabis-specific risk factors in particular and go beyond considerations of harm from regular use. Future studies should replicate these findings with other samples.

In harm's way: Do college students' beliefs about cannabis put them at risk for use?

Objective: This study describes beliefs held by college students about cannabis use and examines the association between three specific cannabis beliefs and likelihood of use. Participants: 3,720 undergraduate students ages 18 to 25 attending ten colleges in one state. Methods: Data were gathered via online survey. Results: The majority (80%) of the sample was unsure or believed that cannabis was an effective way to reduce stress; 67% were unsure or believed that cannabis was not related to an increased risk for mental health problems; and 62% were unsure or believed that students who use cannabis are not more academically disengaged. Holding these beliefs, which are not supported by scientific evidence, was associated with a greater likelihood of cannabis use, even after statistically adjusting for covariates. Conclusions: These findings suggest that beliefs unsupported by scientific evidence are widespread among college students. Dispelling misinformation about cannabis might hold promise for reducing use.

A qualitative examination of college students' perceptions of cannabis: insights into the normalization of cannabis use on a college campus

ObjectiveThis study aimed to qualitatively examine how perceptions of cannabis differ among college students in an effort to better understand the changing landscape of cannabis on college campuses. Participants: Forty-six predominantly male (69.9%; M_age = 23.15, SD = 4.11) college students attending a border state university (i.e., a state that has not yet legalized cannabis but borders a state that has). Methods: Participants engaged in facilitated focus group discussions (N = 5) about cannabis-related issues. Results: Thematic analysis uncovered three primary themes and six subthemes. Main themes included: 1) User Heterogeneity and Identity, 2) Relative Benefits and Harms of Cannabis, and 3) Social Position of Cannabis on Campus Culture. Conclusions: Cannabis has quickly integrated into the college social environment, with social stigmatization and identification with cannabis impacting decisions to use. Findings inform existing college health programs on how to approach conversations about cannabis with students.

Heterogeneous health effects of medical marijuana legalization: Evidence from young adults in the United States

Legalizing marijuana for medical purposes is a longstanding debate. However, evidence of marijuana's health effects is limited, especially for young adults. We estimate the health impacts of medical marijuana laws (MML) in the U.S. among young adults aged 18-29 years using the difference-in-differences method and data from the Behavioral Risk Factors Surveillance System. We find that having MMLs with strict regulations generate health gains, but not in states with lax regulations. Our heterogeneity analysis results indicate that individuals with lower education attainments, with lower household income and without access to health insurance coverage gain more health benefits from MML with strict regulations than from MML with lax regulations. The findings suggest greater net health gains under strict controls concerning marijuana supply and access.

Societal Costs and Outcomes of Medical and Recreational Marijuana Policies in the United States: A Systematic Review

Significant support exists in the United States for legalization of marijuana/cannabis. As of 2021, 36 states and four territories approved the legalization of medical cannabis via medical marijuana laws (MMLs), and 15 states and District of Columbia (DC) have adopted recreational marijuana laws (RMLs). We performed structured and systematic searches of articles published from 2010 through September 2021. We assess the literature pertaining to adolescent marijuana use; opioid use and opioid-related outcomes; alcohol use; tobacco use; illicit and other drug use; marijuana growing and cultivation; employment, earnings, and other workplace outcomes; academic achievement and performance; criminal activity; perceived harmfulness; traffic and road safety; and suicide and sexual activity. Overall, 113 articles satisfied our inclusion criteria. Except for opioids, studies on use of other substances (illicit drugs, tobacco, and alcohol) were inconclusive. MMLs and RMLs do not generate negative outcomes in the labor market, lead to greater criminal activity, or reduce traffic and road safety.

Trends in cannabis-related attitudes and behaviors among cannabis-using adolescent and young adult outpatients following medical cannabis legalization in Massachusetts

Background: Among youth already using cannabis, legalization of medical cannabis may influence cannabis-related attitudes and behaviors, including increasing access through use of someone else's medical cannabis (diversion). Objective: To examine cannabis-related attitudes and behaviors (including diverted cannabis use) in cannabis-using youth in the four years following medical cannabis legalization. Additionally, we investigated characteristics of youth who used vs. did not use diverted medical cannabis. Methods: Data were collected in Boston from 2013 (when medical cannabis legislation took effect in Massachusetts) through 2016 (when recreational cannabis use became legal in Massachusetts). Cannabis-using youth (age 13-24) presenting to an outpatient adolescent substance use treatment program (ASUTP) or recruited for an adolescent medicine clinic study (AMCS) completed a confidential survey on demographic characteristics and cannabis use behaviors and attitudes. We used multiple logistic regression to analyze changes in attitudes and behaviors over three years versus the reference year (2013), controlling for demographics. We used chi-square to compare characteristics of youth reporting use of diverted medical cannabis versus those not. Results: The sample included 273 cannabis-using youth (ASUTP n = 203, AMCS n = 70; 2013 n = 67, 2014 n = 67, 2015 n = 77, 2016 n = 62). Mean ± SD age was 18.2 ± 2.5 years, 32% were female, 58% were White non-Hispanic, and 70% had college-graduate parents. In 2013, most youth reported that cannabis was easy to obtain (97.9%), and that occasional cannabis use had "no" or "slight" risk of harm (89.4%), with little change across years. In 2016, 44% of youth reported using someone else's medical cannabis, versus 15% in 2013 (aOR 4.66, 95% CI 1.81, 11.95). Youth using diverted medical cannabis had higher likelihood of reporting riding with a driver, or driving themselves, after cannabis use (both p < .01). Conclusion: Among at-risk youth in Massachusetts, use of diverted medical cannabis increased after medical cannabis legalization, and those using diverted medical cannabis reported higher risk for cannabis-related traffic injury.

A Systematic Review of Trends in US Attitudes toward Cannabis Legalization

METHODS

A systematic search was conducted for publications in PubMed, EMBASE, and PsycINFO up to October 2019. Six studies with a regionally or nationally representative adult US-based populations were included. A secondary analysis was conducted using data from the National Survey of Drug Use and Health. Hierarchical age-period-cohort analysis assessed the trends in perceived harmfulness and availability of cannabis between 1996 and 2018. Ecological comparisons were made between these perceptions and support for cannabis legalization over time.

RESULTS

A steep growth in support for cannabis legalization began in the 1990s and continued to grow in a relatively linear manner. Most people developed more liberal views, with no evidence that changes within any one sociodemographic group was disproportionately responsible for the overall attitudinal change. Increases in the proportion of people who use cannabis, non-religious population and political liberalism may partially explain the increased support for legalization. The decline in perceived harmfulness of cannabis, as reflected in the media, may have contributed to the increased support for legalization. However, perceptions of the availability of cannabis remained stable despite significant relaxations in cannabis regulations.

CONCLUSIONS

The US population has become more accepting of cannabis legalization. The attitudinal change is related to changes in the perceived risks and benefits of cannabis use, influenced by broader political and cultural changes over the study period.

Adverse childhood experiences and adolescent nicotine and marijuana vaping: Findings from a statewide sample of Florida youth

A wealth of research links exposure to adverse childhood experiences (ACEs) with negative outcomes including nicotine and marijuana use. In addition, an emerging line of research has documented associations between exposure to ACEs and vaping activity in American adults and international samples of adolescents. Very limited research, however, has explored whether a history of ACEs is linked with adolescent nicotine and marijuana vaping activity in an American sample. This study addresses this gap in the literature by employing multinomial logistic regression to examine whether cumulative exposure to ACEs is associated with adolescent nicotine vaping, dual mode use of nicotine, marijuana vaping, and dual mode use of marijuana in a sample of Florida high school students. Our findings reveal that greater cumulative exposure to ACEs (up to 5 ACEs) in adolescents leads to an increase in the likelihood of vaping nicotine and marijuana. In addition, greater cumulative exposure to ACEs (up to 6 ACEs) leads to an increase in the likelihood of using nicotine and marijuana through multiple delivery modes.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Marijuana liberalization policies and perinatal health

We studied the effect of marijuana liberalization policies on perinatal health with a multiperiod difference-in-differences estimator that exploited variation in effective dates of medical marijuana laws (MML) and recreational marijuana laws (RML). We found that the proportion of maternal hospitalizations with marijuana use disorder increased by 23% (0.3 percentage points) in the first three years after RML implementation, with larger effects in states authorizing commercial sales of marijuana. This growth was accompanied by a 7% (0.4 percentage points) decline in tobacco use disorder hospitalizations, yielding a net zero effect over all substance use disorder hospitalizations. RMLs were not associated with statistically significant changes in newborn health. MMLs had no statistically significant effect on maternal substance use disorder hospitalizations nor on newborn health and fairly small effects could be ruled out. In absolute numbers, our findings implied modest or no adverse effects of marijuana liberalization policies on the array of perinatal outcomes considered.

Young adult cannabis use disorder treatment admissions declined as past month cannabis use increased in the U.S.: An analysis of states by year, 2008-2017

OBJECTIVE

This short communication reports on the association of annual measures of young adult (age 18-24) past month cannabis use with cannabis use disorder (CUD) treatment admissions by state in the U.S. from 2008 to 2017.

METHODS

Annual data on percentage of past month cannabis use and the total number of CUD treatment admissions among young adults were acquired for each state from SAMHSA NSDUH and TEDS-A data sets. For each state, the correlation over time between cannabis use and treatment admissions rate was calculated and visualized in a choropleth map. Fixed-effects regression, where effects are fixed by state, was used to investigate the association of cannabis use with treatment admissions rate.

RESULTS

In 38 out of 50 states, including seven out of the eight states legalizing recreational cannabis during the study period, as young adult cannabis use increased, treatment admissions declined. Cannabis use is significantly and negatively associated with treatment admissions (β = -7.21, 95% CI = -11.88, -2.54), even after controlling for health insurance coverage, criminal justice referral, treatment center availability, and cannabis legalization status.

CONCLUSIONS

While it is possible that across the U.S. more young adults are using cannabis without developing CUD, we speculate that increasing social acceptance of cannabis use, and declining perception of harm, may influence treatment seeking behavior, potentially resulting in growing unmet need for CUD treatment among young adults. Monitoring state-level trends in cannabis use, CUD prevalence, and treatment admissions is key to developing CUD prevention and treatment policies targeted to timely, state-specific conditions.

Attitudes and beliefs about recreational cannabis legalization among cannabis-using young adults in Los Angeles: Impact on concurrent cannabis practices and problematic cannabis use

BACKGROUND

This study investigated differences in attitudes and beliefs about recreational cannabis legalization (RCL) among cannabis-using young adults comprised of medical cannabis patients (MCP) and non-patient users (NPU). We further investigated whether these variations are associated with concurrent cannabis practices and problematic use.

METHOD

Cannabis-using young adults (N = 301) were interviewed between 2017 and 2018 - after RCL and through the early months after storefront sales began. Latent class analysis empirically derived groups based on participants' attitudes/beliefs about the impact of RCL. Socio-demographic factors, patient status, medicinal and/or recreational use, and social norms differentiated latent class memberships, while concurrent cannabis practices and problematic use served as distal outcomes. The manual Bolck, Croon, and Hagenaars (BCH) three-step process modeled all covariates and distal outcomes simultaneously in the final LCA solution.

RESULTS

Three patterns emerged: Impacted (RCL had broad impact on attitudes/beliefs) (n = 113), Partially-Impacted (RCL had some impact on attitudes/beliefs) (n = 131) and Neutral (RCL had no/limited impact) (n = 57). MCP were more likely to be Neutral than Partially-Impacted users while those who reported recreational cannabis use were more likely to be Impacted than Neutral users. Class membership predicted cannabis practices and problematic use with Impacted individuals reporting the greatest recent days of use, number of hits per day, and highest scores in problematic cannabis use compared to Partially-Impacted and Neutral users.

CONCLUSION

Variability in attitudes/beliefs about RCL served as strong drivers of concurrent cannabis practices and problematic use. Findings provide an important baseline for tracking attitudes/beliefs' long-term health and substance use impact as retail cannabis sales evolve.

Joint perceptions of the risk and availability of Cannabis in the United States, 2002-2018

BACKGROUND

Prior work suggests that perceived risk and perceived availability of cannabis independently affect cannabis use. However, perceived risk likely modifies the effect of perceived availability, and vice versa. This study explored trends in joint perceived risk and availability of cannabis from 2002 to 2018 and the relationship between combined perceptions and cannabis use, frequent use, and cannabis use disorder (CUD).

METHODS

National Surveys on Drug Use and Health data (n = 949,285, ages 12+) were used to create combined categories of perceived risk of weekly cannabis use and perceived cannabis availability. Descriptive analyses compared joint perceived risk/availability trends (pre/post-2015 due to survey redesign) overall and stratified by age, gender, past-year cannabis use, frequent use, and CUD. Regression analysis estimated associations between perceived risk/availability and cannabis outcomes.

RESULTS

From 2002 to 2018, the prevalence of perceiving cannabis as low-risk doubled while perceiving cannabis as available remained unchanged. The proportion of individuals perceiving cannabis as Low-risk/Available increased by 86% from 2002 to 2014 (16.8%-31.2%) and 19% from 2015 to 2018 (30.1%-35.8%) while High-risk/Available and High-risk/Unavailable proportions declined. Differing patterns were observed by age and gender. Compared with individuals perceiving cannabis as High-risk/Unavailable, people in all other perception categories had greater risk of all cannabis outcomes. Results were consistent with additive interaction between perceived risk and availability in their effects on cannabis use.

CONCLUSIONS

Trends and associations with cannabis outcomes differ when considering perceived risk and availability independently versus jointly. Longitudinal studies and cannabis policy evaluations would advance understanding of links between cannabis perceptions and use.

The effect of medical cannabis laws on pharmaceutical marketing to physicians

Although cannabis is federally prohibited, a majority of U.S. states have implemented medical cannabis laws (MCLs). As more individuals consider the drug for medical treatment, they potentially substitute away from prescription drugs. Therefore, an MCL signals competitor entry. This paper exploits geographic and temporal variation in MCLs to examine the strategic response in direct-to-physician marketing by pharmaceutical firms as cannabis enters the market. Using office detailing records from 2014-2018 aggregated to the county level, we find weak evidence of a relatively small and delayed response in substitute prescription drug- and opioid-related detailing. While these effects on detailing dollars are more pronounced among smaller pharmaceutical firms, the magnitudes are economically small and likely muted at aggregate levels by the small percent of doctors that actively recommend cannabis for medical treatment.

Effect of Washington State and Colorado's cannabis legalization on death by suicides

In the U.S., death by suicide is a leading cause of death and was the 2nd leading cause of death for ages 15-to-34 in 2018. Though incomplete, much of the scientific literature has found associations between cannabis use and death by suicide. Several states and the District of Columbia have legalized cannabis for general adult use. We sought to evaluate whether cannabis legalization has impacted suicide rates in Washington State and Colorado, two early adopters. We used a quasi-experimental research design with annual, state-level deaths by suicide to evaluate the legalization of cannabis in Washington State and Colorado. We used synthetic control models to construct policy counterfactuals as our primary method of estimating the effect of legalization, stratified by age, gender, and race/ethnicity. Overall death by suicide rates were not impacted in either state. However, when stratified by age categories, deaths by suicide increased 17.9% among 15-24-year-olds in Washington State, or an additional 2.13 deaths per 100,000 population (p-value ≤0.001). Other age groups did not show similar associations. An ad hoc analysis revealed, when divided into legal and illegal consumption age, 15-20-year olds had an increase in death by suicides of 21.2% (p-value = 0.026) and 21-24-year olds had an increase in death by suicides of 18.6% (p-value ≤0.001) in Washington State. The effect of legalized cannabis on deaths by suicide appears to be heterogeneous. Deaths by suicide among 15-24-year-olds saw significant increases post-implementation in Washington State but not in Colorado.

Demographic and policy-based differences in behaviors and attitudes towards driving after marijuana use: an analysis of the 2013-2017 Traffic Safety Culture Index

OBJECTIVE

Marijuana policies in the United States have become more permissive, motivating research on demographic and policy-based differences in behaviors and attitudes towards driving after marijuana use. The Traffic Safety Culture Index is an annual survey with national scope and multiple measures relevant to driving after marijuana use. We tabulated responses to questions about driving after marijuana use from the Traffic Safety Culture Index based on demographic factors, recreational and medical marijuana policies, and per-se marijuana laws.

RESULTS

Male, younger, lower-income, and lower-education respondents self-reported driving after marijuana use more than their demographic counterparts, more often reported such behavior to be personally acceptable, and exhibited lower support per-se laws. Drivers in states that legalized medical marijuana self-reported driving after marijuana use slightly more than drivers in states where both medical and recreational were illegal. Support for per-se laws was higher among those in states that legalized recreational marijuana and in states with per-se laws. Demographic differences in our outcomes were consistent and cohesive. On the other hand, we found no predominant pattern suggesting that those in states with liberal marijuana policies were more tolerant of driving after marijuana use.

Associations of cannabis use disorder with cognition, brain structure, and brain function in African Americans

Although previous studies have highlighted associations of cannabis use with cognition and brain morphometry, critical questions remain with regard to the association between cannabis use and brain structural and functional connectivity. In a cross-sectional community sample of 205 African Americans (age 18-70) we tested for associations of cannabis use disorder (CUD, n = 57) with multi-domain cognitive measures and structural, diffusion, and resting state brain-imaging phenotypes. Post hoc model evidence was computed with Bayes factors (BF) and posterior probabilities of association (PPA) to account for multiple testing. General cognitive functioning, verbal intelligence, verbal memory, working memory, and motor speed were lower in the CUD group compared with non-users (p < .011; 1.9 < BF < 3,217). CUD was associated with altered functional connectivity in a network comprising the motor-hand region in the superior parietal gyri and the anterior insula (p < .04). These differences were not explained by alcohol, other drug use, or education. No associations with CUD were observed in cortical thickness, cortical surface area, subcortical or cerebellar volumes (0.12 < BF < 1.5), or graph-theoretical metrics of resting state connectivity (PPA < 0.01). In a large sample collected irrespective of cannabis used to minimize recruitment bias, we confirm the literature on poorer cognitive functioning in CUD, and an absence of volumetric brain differences between CUD and non-CUD. We did not find evidence for or against a disruption of structural connectivity, whereas we did find localized resting state functional dysconnectivity in CUD. There was sufficient proof, however, that organization of functional connectivity as determined via graph metrics does not differ between CUD and non-user group.

Gender differences in the risk and protective factors of marijuana use among U.S. College students

Gender differences in the risk and protective factors of marijuana use among college students were explored by analyzing online survey responses from 464 undergraduates. Women perceived higher risk and used marijuana less than men, with no gender difference in peer disapproval. In addition, women had higher objective knowledge regarding the health effects of marijuana, although they exhibited lower confidence in their knowledge. In subsequent regression analyses, health knowledge, confidence in knowledge, perceived risk, and peer disapproval predicted women's marijuana use, whereas only confidence in knowledge and perceived risk predicted men's use. These findings can help devise effective intervention strategies.

A longitudinal study of the impact of marijuana on adult memory function: Prenatal, adolescent, and young adult exposures

More Americans are using marijuana than in previous decades but there are concerns over its long-term impact on cognitive functioning, especially memory. The literature on marijuana use and cognitive functioning is mixed, with some studies showing recovery of functioning upon abstinence from the drug and others showing long-term effects that persist. The latter seems especially true for individuals who initiate marijuana at a younger age and engage in more chronic patterns of use. The goal of the current study is to use prospectively collected data on young adults from a prenatal cohort to determine if there is an effect of early and/or current marijuana use on young adult memory, controlling for prenatal exposure to marijuana use, childhood memory deficits, and other significant covariates of memory functioning. At the 22-year follow-up phase of the Maternal Health Practices and Child Development (MHPCD) study, 524 young adults (58% Black, 42% White, 52% female) completed the Wechsler Memory Scale-III. Multiple regression analyses and structural equation modeling were used to determine the effect of marijuana exposure during gestation, early adolescence, and young adulthood on young adult memory function. Results indicated that initiating marijuana use before age 15 placed young adults at greater risk of memory deficits, even after controlling for childhood memory and current marijuana use. First trimester marijuana exposure also indirectly predicted young adult memory function via childhood memory deficits and early initiation of marijuana. These findings highlight the risk of prenatal marijuana exposure and early initiation of marijuana for long-term memory function in adulthood.

The associations of medical marijuana policies with opioid-related health care utilization

OBJECTIVE

To examine the associations between medical marijuana policies and opioid-related hospitalizations and emergency department visits.

DATA SOURCES

We utilized quarterly rates of hospital discharge data from the Healthcare Cost and Utilization Project's (HCUP) Fast Stats Database from 2005 to 2016 along with state-level sociodemographic data from US Census Bureau and Bureau of Labor Statistics and opioid-related state health policy data from publicly available sources for the analysis.

STUDY DESIGN

Analyses were carried out using a difference-in-differences regression approach. We estimate heterogeneous effects of medical marijuana policies such as initial policy, presence of active dispensary, and home cultivation on opioid-related hospitalizations and emergency department visits related to opioids.

DATA COLLECTION/EXTRACTION METHODS

Publicly available secondary data were collected, linked, and analyzed. Observations with missing values for explanatory variables were excluded from the analysis.

PRINCIPAL FINDINGS

Regression results indicate that type of medical marijuana policy has varying effects on opioid-related hospitalizations and emergency department visits. States that allow home cultivation of medical marijuana experienced significant positive associations with opioid-related hospitalizations and emergency department visits, while no effect was observed with medical marijuana dispensaries. Moreover, recreational marijuana policies were positively associated with opioid-related hospitalizations.

CONCLUSIONS

The findings indicate that the effects of medical marijuana policies on opioid-related hospitalizations and emergency department visits vary depending on the type of medical marijuana policy. Our findings indicate that the implementation of home cultivation of marijuana is positively associated with hospitalizations and emergency department visits related to opioids, suggesting that easier access to marijuana among opioid users may result in adverse health conditions that need treatment.

Impact of state-level cannabis legalization on poly use of alcohol and cannabis in the United States, 2004-2017

BACKGROUND

Cannabis policy has shifted toward legalization in many parts of the United States (US). While attention has been focused on whether legalization will lead to changes in cannabis use, it is conceivable that legalization will also affect use of substances that individuals frequently use with cannabis. This study assessed whether cannabis legalization impacted the prevalence of poly use of cannabis and alcohol from 2004 to 2017 and estimated the prevalence of cannabis and alcohol poly use in 2017.

METHODS

Public and restricted-use data from the US 2004-2017 National Survey on Drug Use and Health were analyzed. Data on past-month cannabis and alcohol use were assessed each year. Cannabis legalization was determined by the presence or absence of medical marijuana laws (MML) and recreational marijuana laws (RML) in each state. Difference-in-difference approach was used to estimate the association of MML and RML on cannabis and alcohol use overall and by sociodemographic subgroups (e.g., age, income, education).

RESULTS

Between 2004 and 2017, poly use of cannabis and alcohol increased while alcohol-only use decreased. MML were associated with increases in poly use only among adults over age 50 and among those with higher annual incomes and higher education, while RML were associated with increases in poly use broadly among adults across sociodemographic groups.

CONCLUSIONS

Legalization of cannabis was associated with increases in cannabis-alcohol poly use in the US. RML were associated with increases across demographics, while the impact of MML was more limited to certain sociodemographic groups.

Personal Correlates of Support for Medical and Recreational Cannabis Legalization in Australia

Introduction and Aims: Increasingly more Australians are in favor of legalizing medical and recreational cannabis use. This paper explored the personal characteristics of those who supported each of these policies in Australia. Design: Cross-sectional national survey. Methods: This study included 21,729 participants aged 18 years and above who responded to the 2016 National Drug Strategy Household Survey. Participants were provided the assurance of confidentiality for their participations. Logistic regression models were used to examine the relationships between personal characteristics and support for the legalization of medical and recreational cannabis. Results: Overall, 77 and 40% of participants supported the legalization of medical and recreational cannabis respectively. People of older age were more likely to support medical cannabis legalization while those who supported legalization of recreational cannabis use were more likely to be younger. Medical cannabis supporters were more likely to report chronic pain (OR = 1.44, 95% CI: 1.04, 2.00) while recreational cannabis supporters were more likely to suffer high level of psychological distress (OR = 1.28, 95% CI: 1.14, 1.43). Experience with cannabis use was strongly associated with supportive attitudes, with recent cannabis users almost 14 times (OR = 14.13, 95% CI: 5.37, 37.20) and 34 times (OR = 33.74, 95% CI: 24.22, 47.01) more likely to support the legalization of medical and recreational cannabis use, respectively. Discussion and Conclusions: The majority of Australians approve the legalization of cannabis for medicinal purposes but most remain cautious about legalizing recreational cannabis use. The sociodemographic and clinical profile of supporters of medical and recreational legalization suggests a potential interaction of self-interests and beliefs about the harms of cannabis use.

U.S. College Students' Marijuana Information Sources, Confidence in Knowledge, and Objective Knowledge

In recent years, marijuana use on U.S. college campuses reached the highest point while the perceptions of risk and social disapproval registered the lowest since the early 1980s. However, little attention has been paid to the sources of the marijuana-related messages and their relationships with marijuana knowledge and confidence in knowledge, proximate protective/risk factors. To fill this gap, a convenience sample of students (N = 249) on a campus located in a U.S. recreational marijuana legal state were surveyed to identify their marijuana information sources and explore the relationships among the sources, confidence in marijuana knowledge, and objective knowledge. Peers/media were the most important sources and they were used more than other sources. Use of peers/media sources was related to lower health knowledge and higher confidence in knowledge. Although students named parents and education/science sources as important, these were less frequently used than siblings, the sources they named as the least important. This study advanced our understanding of the various sources of marijuana information used by U.S. college students and the relationships between the information sources and confidence in knowledge and objective knowledge, two emerging risk/protective factors in the era of marijuana deregulation.

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.

Neural and behavioral correlates associated with adolescent marijuana use

Purpose of Review

Marijuana (MJ) is one of the most commonly used drugs among adolescents. Exposure to MJ during adolescence can lead to alterations in brain development, and, subsequently to the behavioral correlates regulated by the affected brain regions. In this review, we discuss findings from preclinical and human studies examining the relationship between adolescent MJ use and the neurobiological and behavioral correlates associated with it.

Recent Findings

Current findings indicate that adolescent MJ use is associated with alterations in brain structure and function, especially in regions that express high levels of the cannabinoid 1 receptor such as the prefrontal cortex, hippocampus, cerebellum and limbic regions. These alterations are correlated with changes in affective, cognitive and reward-seeking behavior. Furthermore, evidence suggests that exposure to MJ during adolescence can have long-lasting and pronounced neural and behavioral effects into adulthood.

Summary

The wide ranging neural and behavioral correlates associated with MJ use during adolescence highlight the need for further studies to better understand the potential risk factors and/or neurotoxic effects of adolescent MJ use.

State medical marijuana laws, cannabis use and cannabis use disorder among adults with elevated psychological distress

BACKGROUND

Cannabis use and cannabis use disorder are more prevalent in U.S. states with medical marijuana laws (MMLs), as well as among individuals with elevated psychological distress. We investigated whether adults with moderate and serious psychological distress experienced greater levels of cannabis use and/or disorder in states with MMLs compared to states without MMLs.

METHODS

National Survey of Drug Use and Health data (2013-2017) were used to compare past-month cannabis use, daily cannabis use, and cannabis use disorder prevalence among adults with moderate and serious psychological distress in states with versus without MMLs. We executed pooled multivariable logistic regression analyses to test main effects of distress, MMLs and their interaction, after adjustment.

RESULTS

Compared to states without MMLs, states with MMLs had higher adjusted prevalence of past-month use (11.1 % vs. 6.8 %), daily use (4.0 % vs. 2.2 %), and disorder (1.7 % vs. 1.2 %). Adults with moderate and serious psychological distress had greater adjusted odds of any use (AORs of 1.72 and 2.22, respectively) and of disorder (AORs of 2.17 and 2.94, respectively), compared to those with no/mild distress. We did not find evidence of an interaction between MMLs and distress category for any outcome.

CONCLUSIONS

Associations between elevated distress and cannabis use patterns are no greater in states with MML. However, cannabis use is more prevalent in MML states. Thus, higher base rates of cannabis use and disorder among adults with elevated distress are proportionally magnified in these states.

Changes in the Order of Cigarette and Marijuana Initiation and Associations with Cigarette Use, Nicotine Vaping, and Marijuana Use: U.S. 12th Grade Students, 2000-2019

This study (a) examined changes in marijuana and cigarette initiation sequencing and (b) considered implications of such changes for prevention efforts by examining associations between initiation sequencing and current adolescent substance use. Analyses used 2000-2019 cross-sectional data from the national Monitoring the Future (MTF) study (78,252 U.S. 12th grade students). Models examined trends in six distinct patterns of initiation order, and multivariable associations between order of initiation and 30-day cigarette and marijuana use prevalence, cigarette and marijuana use frequency among users, and nicotine and marijuana vaping prevalence. While the percentage of students initiating neither cigarettes nor marijuana increased, increases also were observed in marijuana-only initiation (the fastest-growing pattern) and initiation of marijuana before cigarettes; these increases were accompanied by a significant decrease in cigarette-only initiation. Cigarette use prevalence and frequency were highest among students initiating cigarettes before marijuana; marijuana use prevalence and frequency were highest among students initiating marijuana before cigarettes. Cigarette and marijuana prevalence, as well as marijuana frequency, were lowest among students initiating only a single substance. Nicotine vaping was less prevalent among students initiating a single substance versus both substances, but no significant differences were observed in nicotine vaping prevalence between those initiating only cigarettes versus only marijuana. Implications of these findings for prevention efforts are discussed in the frameworks of both the common liability model and route of administration model.

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.

Long-term effects of maternal cannabis vapor exposure on emotional reactivity, social behavior, and behavioral flexibility in offspring

The use of cannabis during pregnancy is a growing public health concern. As more countries implement legislation permitting recreational cannabis use, there is an urgent need to better understand its impact on fetal neurodevelopment and its long-term effects in exposed offspring. Studies examining effects of prenatal cannabis exposure typically employ injections of synthetic cannabinoids or isolated cannabis constituents that may not accurately model cannabis use in human populations. To address this limitation, we developed a novel e-cigarette technology-based system to deliver vaporized cannabis extracts to pregnant Long Evans rats. We used this model to determine effects of prenatal cannabis exposure on emotional, social, and cognitive endpoints of male and female offspring during early development and into adulthood. Dams were exposed to cannabis vapor (CAN_THC: 400 mg/ml), vehicle vapor (VEH), or no vapor (AIR) twice daily during mating and gestation. Offspring exposed to CAN_THC and VEH showed reduced weight gain relative to AIR offspring prior to weaning. CAN_THC offspring made more isolation-induced ultrasonic vocalizations (USVs) on postnatal day 6 (P6) relative to VEH-exposed offspring, which is indicative of increased emotional reactivity. Male CAN_THC offspring engaged in fewer social investigation behaviors than VEH-exposed male offspring during a social play test on P26. In adulthood, CAN_THC-exposed offspring spent less time exploring the open arms of the elevated plus maze and exhibited dose-dependent deficits in behavioral flexibility in an attentional set-shifting task relative to AIR controls. These data collectively indicate that prenatal cannabis exposure may cause enduring effects on the behavioral profile of offspring.

Association of Depression With Past-Month Cannabis Use Among US Adults Aged 20 to 59 Years, 2005 to 2016

IMPORTANCE

Despite studies showing that repeated cannabis use may worsen depressive symptoms, the popular media increasingly presents cannabis as beneficial to mental health, and many members of the public view cannabis as beneficial for depression. Therefore, cannabis use among individuals with depression may be becoming more prevalent.

OBJECTIVE

To examine the association of depression with past-month cannabis use among US adults and the time trends for this association from 2005 to 2016.

DESIGN, SETTING, AND PARTICIPANTS

This repeated cross-sectional study used data from 16 216 adults aged 20 to 59 years who were surveyed by the National Health and Nutrition Examination Survey, a national, annual, cross-sectional survey in the United States, between 2005 and 2016. Data analysis was conducted from January to February 2020.

EXPOSURES

Survey year and depression, as indicated by a score of at least 10 on the Patient Health Questionnaire-9.

MAIN OUTCOMES AND MEASURES

Any past-month cannabis use (ie, ≥1 use in the past 30 days) and daily or near-daily past-month cannabis use (ie, ≥20 uses in the past 30 days). Logistic regression was used to examine time trends in the prevalence of cannabis use, depression, and the association between cannabis use and depression from 2005 to 2016.

RESULTS

The final analysis included 16 216 adults, of whom 7768 (weighted percentage, 48.9%) were men, 6809 (weighted percentage, 66.4%) were non-Hispanic White participants, and 9494 (weighted percentage, 65.6%) had at least some college education. They had a weighted mean age of 39.12 (95% CI, 38.23-39.40) years. Individuals with depression had 1.90 (95% CI, 1.62-2.24) times the odds of any past-month cannabis use and 2.29 (95% CI, 1.80-2.92) times the odds of daily or near-daily cannabis use compared with those without depression. The association between cannabis use and depression increased significantly from 2005 to 2016. The odds ratio for depression and any past-month cannabis use increased from 1.46 (95% CI, 1.07-1.99) in 2005 to 2006 to 2.30 (95% CI, 1.82-2.91) in 2015 to 2016. The odds ratio for depression and daily or near-daily past-month cannabis use increased from 1.37 (95% CI, 0.81-2.32) in 2005 to 2006 to 3.16 (95% CI, 2.23-4.48) in 2015 to 2016.

CONCLUSIONS AND RELEVANCE

The findings of this study indicate that individuals with depression are at increasing risk of cannabis use, with a particularly strong increase in daily or near-daily cannabis use. Clinicians should be aware of these trends and the evidence that cannabis does not treat depression effectively when discussing cannabis use with patients.

State Medical Marijuana Laws and Associated Marijuana Use, Attitudes, and Perceived Social Norms among Adolescents in the U.S

Statewide medical marijuana laws (MMLs) in the U.S. may be associated with adolescent marijuana use behavior, attitudes toward marijuana use, and social norms. This study used data from the National Study on Drug Use and Health (2013-2016) to examine the associations of state MML with marijuana use, use frequency, and attitudes and perceived peer and parental social norms toward using marijuana. Propensity-score matching was used to reduce selection bias between states with and without MML (matched N = 50,000). Results showed that adolescents residing in states with MML had higher odds of using marijuana in the past month and past year (OR = 1.45 and 1.49; ps < .001), higher marijuana use frequencies in the past month (β = 0.12, p < .001), relatively more neutral attitudes toward marijuana use (β = - 0.06, p < .001), and weaker perception of peer and parental disapproval of marijuana use (β = - 0.04 and -0.02, ps < .001). Our findings suggested that for the states that have implemented MML, special efforts should be strengthened to prevent and reduce adolescent marijuana use. For the states that have not yet implemented MML, the associations between MML and adolescent marijuana use attitudes and perceived norms should be taken into account when legislating medical marijuana and designing prevention and intervention efforts.

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.

Recreational Marijuana Availability in Oregon and Use Among Adolescents

INTRODUCTION

This study investigated whether legalization of recreational marijuana sales and retail availability of marijuana in Oregon counties were associated with higher levels of marijuana use and related beliefs among adolescents.

METHODS

Biennial data for 6th, 8th, and 11th graders from the 2010-2018 Student Wellness Survey in 35 Oregon counties (n=247,403) were analyzed in 2019 to assess changes in past 30-day marijuana use and beliefs (e.g., perceived availability of marijuana) in counties that allowed recreational marijuana sales in unincorporated areas beginning in October 2015 versus counties that did not. Analyses were also conducted with 2016 and 2018 Student Wellness Survey data (n=101,419) to determine whether the association between allowing recreational marijuana sales and marijuana use could be accounted for by retail marijuana outlet density and beliefs.

RESULTS

Higher rates of past 30-day marijuana use and more favorable beliefs were observed in counties that allow recreational marijuana sales in unincorporated areas, both before and after legalization of recreational sales in 2015. The prevalence of past 30-day marijuana use increased, relative to the downward secular trend, after legalization both in counties that did and did not allow recreational marijuana sales. There were parallel changes in beliefs favorable to marijuana use. Analyses with 2016 and 2018 Student Wellness Survey data suggested that the association between allowing recreational marijuana sales and past 30-day marijuana use could be accounted for by retail marijuana outlet density and beliefs.

CONCLUSIONS

Legalization and greater retail availability of recreational marijuana are positively associated with marijuana use among adolescents.

Marijuana Decriminalization, Medical Marijuana Laws, and Fatal Traffic Crashes in US Cities, 2010-2017

Objectives. To determine the impact of city-level cannabis decriminalization and medical marijuana laws (MMLs) on fatal traffic crashes in US cities.Methods. Using a census of fatal traffic crashes from the 2010 to 2017 Fatality Analysis Reporting System, we examined MMLs and cannabis decriminalization on fatal crashes by age and sex of driver. We used a Poisson difference-in-differences approach, exploiting temporal and geographic variation in marijuana decriminalization laws.Results. Cities experienced a 13% increase in fatal crashes involving 15- to 24-year-old male drivers following decriminalization (incidence rate ratio = 1.125; 95% confidence interval = 1.014, 1.249). This effect was immediate and strongest on weekend nights. We found no effect on female drivers or older males. Conversely, we found that MMLs were associated with fewer fatal crashes for both males and females, which was most pronounced in 15- to 24-year-old drivers.Conclusions. Unlike MMLs, which are associated with fewer fatal crashes, cities experienced a relative increase in fatal crashes involving young male drivers following marijuana decriminalization.Public Health Implications. MMLs stipulate consumption occurs at home, whereas decriminalization only lessens the penalty for marijuana possession. Therefore, travel incentives of such laws have heterogeneous effects on traffic safety.