The effects of medical marijuana laws on illegal marijuana use

Medical marijuana laws and mental health in the United States

The consequences of legal access to medical marijuana for individuals' well-being are controversially assessed. We contribute to the discussion by evaluating the impact of the introduction of medical marijuana laws across US states on self-reported mental health considering different motives for cannabis consumption. Our analysis is based on BRFSS survey data from close to eight million respondents between 1993 and 2018 that we combine with information from the NSDUH to estimate individual consumption propensities. We find that eased access to marijuana through medical marijuana laws reduce the reported number of days with poor mental health for individuals with a high propensity to consume marijuana for medical purposes and for those individuals who likely suffer from frequent pain.

Associations between cannabis policies and state-level specialty cannabis use disorder treatment in the United States, 2004-2019

BACKGROUND

Cannabis use disorder (CUD) treatment prevalence decreased in the US between 2002 and 2019, yet structural mechanisms for this decrease are poorly understood. We tested associations between cannabis laws becoming effective and self-reported CUD treatment.

METHODS

Restricted-use 2004-2019 National Surveys on Drug Use and Health included people ages 12+ classified as needing CUD treatment (i.e., past-year DSM-5-proxy CUD or last/current specialty treatment for cannabis). Time-varying indicators of medical cannabis laws (MCL) with/without cannabis dispensary provisions differentiated state-years before/after laws using effective dates. Multi-level logistic regressions with random state intercepts estimated individual- and state-adjusted CUD treatment odds by MCLs and model-based changes in specialty CUD treatment state-level prevalence. Secondary analyses tested associations between CUD treatment and MCL or recreational cannabis laws (RCL).

RESULTS

Using a broad treatment need sample definition in 2004-2014, specialty CUD treatment prevalence decreased by 1.35 (95 % CI = -2.51, -0.18) points after MCL without dispensaries and by 2.15 points (95 % CI = -3.29, -1.00) after MCL with dispensaries provisions became effective, compared to before MCL. Among people with CUD in 2004-2014, specialty treatment decreased only in MCL states with dispensary provisions (aPD = -0.91, 95 % CI = -1.68, -0.13). MCL were not associated with CUD treatment use in 2015-2019. RCL were associated with lower CUD treatment among people classified as needing CUD treatment, but not among people with past-year CUD.

CONCLUSIONS

Policy-related reductions in specialty CUD treatment were concentrated in states with cannabis dispensary provisions in 2004-2014, but not 2015-2019, and partly driven by reductions among people without past-year CUD. Other mechanisms (e.g., CUD symptom identification, criminal-legal referrals) could contribute to decreasing treatment trends.

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.

Cannabis dispensary staff approaches to counseling on potential contraindications to cannabis use: insights from a national self-report survey

BACKGROUND

Legal cannabis is available in more than half of the United States. Health care professionals (HCPs) rarely give recommendations on dosing or safety of cannabis due to limits imposed by policy and lack of knowledge. Customer-facing cannabis dispensary staff, including clinicians (pharmacists, nurses, physician's assistants), communicate these recommendations in the absence of HCP recommendations. Little is known about how dispensary staff approach individuals with complex medical and psychiatric comorbidities. Using responses from a national survey, we describe how cannabis dispensary staff counsel customers with medical and psychiatric comorbidities on cannabis use and examine whether state-specific cannabis policy is associated with advice given to customers.

METHODS

National, cross-sectional online survey study from February 13, 2020 to October 2, 2020 of dispensary staff at dispensaries that sell delta-9-tetrahydrocannabinol containing products. Measures include responses to survey questions about how they approach customers with medical and psychiatric comorbidities; state medicalization score (scale 0-100; higher score indicates more similarity to regulation of traditional pharmacies); legalized adult-use cannabis (yes/no). We conducted multiple mixed effects multivariable logistic regression analyses to understand relationships between state medicalization and dispensary employees' perspectives.

RESULTS

Of 434 eligible respondents, most were budtenders (40%) or managers (32%), and a minority were clinicians (18%). State medicalization score was not associated with responses to most survey questions. It was associated with increased odds of encouraging customers with medical comorbidities to inform their traditional HCP of cannabis use (Odds ratio [OR]=1.2, 95% confidence interval [CI] 1.0-1.4, p=0.03) and reduced odds of recommending cannabis for individuals with cannabis use disorder (CUD) (OR=0.8, 95% CI 0.7-1.0, p=0.04). Working in a state with legalized adult-use cannabis was associated with recommending traditional health care instead of cannabis in those with serious mental illness (OR 2.2, 95% CI 1.1-4.7, p=0.04). Less than half of respondents believed they had encountered CUD (49%), and over a quarter did not believe cannabis is addictive (26%).

CONCLUSIONS

When managing cannabis dosing and safety in customers with medical and psychiatric comorbidity, dispensary staff preferred involving individuals' traditional HCPs. Dispensary staff were skeptical of cannabis being addictive. While state regulations of dispensaries may impact the products individuals have access to, they were not associated with recommendations that dispensary staff gave to customers. Alternative explanations for dispensary recommendations may include regional or store-level variation not captured in this analysis.

Recreational marijuana laws and the misuse of prescription opioids: Evidence from National Survey on Drug Use and Health microdata

Several studies have concluded that legalizing medical marijuana can reduce deaths from opioid overdoses. Drawing on micro data from the National Survey on Drug Use and Health, a survey uniquely suited to assessing patterns of substance use, we examine the relationship between recreational marijuana laws (RMLs) and the misuse of prescription opioids. Using a standard difference-in-differences (DD) regression model, we find that RML adoption reduces the likelihood of frequently misusing prescription opioids such as OxyContin, Percocet, and Vicodin. However, using a two-stage procedure designed to account for staggered treatment and dynamic effects, the DD estimate of relationship between RML adoption and the likelihood of frequently misusing prescription opioids becomes positive. Although event study estimates suggest that RML adoption leads to a decrease in the frequency of prescription opioid abuse, this effect appears to dissipate after only 2 or 3 years.

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.

Medical cannabis and automobile accidents: Evidence from auto insurance

While many states have legalized medical cannabis, many unintended consequences remain under-studied. We focus on one potential detriment-the effect of cannabis legalization on automobile safety. We examine this relationship through auto insurance premiums. Employing a modern difference-in-differences framework and zip code-level premium data from 2014 to 2019, we find that premiums declined, on average, by $22 per year following medical cannabis legalization. The effect is more substantial in areas near a dispensary and in areas with a higher prevalence of drunk driving before legalization. We estimate that existing legalization has reduced health expenditures related to auto accidents by almost $820 million per year with the potential for a further $350 million reduction if legalized nationally.

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.

Illegal drug market responses to state recreational cannabis laws

BACKGROUND AND AIMS

In the United States, 15 states and the District of Columbia have implemented recreational cannabis laws (RCLs) legalizing recreational cannabis use. We aimed to estimate the association between RCLs and street prices, potency, quality and law enforcement seizures of illegal cannabis, methamphetamine, cocaine, heroin, oxycodone, hydrocodone, morphine, amphetamine and alprazolam.

DESIGN

We pooled crowdsourced data from 2010-19 Price of Weed and 2010-19 StreetRx, and administrative data from the 2006-19 System to Retrieve Information from Drug Evidence (STRIDE) and the 2007-19 National Forensic Laboratory Information System (NFLIS). We employed a difference-in-differences design that exploited the staggered implementation of RCLs to compare changes in outcomes between RCL and non-RCL states.

SETTING AND CASES

Eleven RCL and 40 non-RCL US states.

MEASURES

The primary outcome was the natural log of prices per gram, overall and by self-reported quality. The primary policy was an indicator of RCL implementation, defined using effective dates.

FINDINGS

The street price of cannabis decreased by 9.2% [β = -0.092; 95% confidence interval (CI) = -0.15-, -0.03] in RCL states after RCL implementation, with largest declines among low-quality purchases (β = -0.195; 95% CI = -0.282, -0.108). Price declines were accompanied by a 93% (β = -0.93; 95% CI = -1.51, -0.36) reduction in law enforcement seizures of cannabis in RCL states. Among illegal opioids, including heroin, oxycodone and hydrocodone, street prices increased and law enforcement seizures decreased in RCL states.

CONCLUSIONS

Recreational cannabis laws in US states appear to be associated with illegal drug market responses in those states, including reductions in the street price of cannabis. Changes in the street prices of illegal opioids analyzed may suggest that in states with recreational cannabis laws the markets for other illegal drugs are not independent of legal cannabis market regulation.

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.

GEOGRAPHICAL ACCESS TO RECREATIONAL MARIJUANA

We investigate whether adult marijuana use in Washington responds to increased local access as measured by drive time to the nearest legal marijuana retailer as well as measures of retail density. Using survey data from the Behavioral Risk Factor Surveillance System, we find that as retailers open closer to where they live, more individuals use marijuana and more frequently. These effects are concentrated among young adults (ages 18-26), women, and rural residents. Controlling for distance to the nearest retailer, we find that whether retail density affects marijuana use depends on how it is measured.

Marijuana legalization and household spending on food and alcohol

Utilizing the Consumer Expenditure Interview Survey from 2005 to 2019, I study spending on food and alcohol following recreational marijuana law (RML). Exploiting differences in the timing of the passage of RMLs and employing two-way fixed-effects methods, I find that households located in states adopting these laws increase their quarterly spending on food, which is driven mainly by spending on food consumed away from home. Legalization of recreational marijuana also leads to increased quarterly spending on alcohol. These findings suggest a complementarity between food, alcohol, and marijuana.

Availability of medical cannabis dispensaries and cannabis abuse/dependence-related hospitalizations in California

AIMS

To estimate associations between both current- and prior-year medical cannabis dispensary densities and hospitalizations for cannabis use disorder in California, USA between 2013 and 2016.

DESIGN

Spatial analysis of ZIP code-level hospitalization discharge data using Bayesian Poisson hierarchical space-time models over 4 years.

SETTING AND CASES

California, USA from 2013 to 2016 (6832 space-time ZIP code units).

MEASUREMENTS

We assessed associations of annual hospitalizations for cannabis use disorder [assignment of a primary or secondary code for cannabis abuse and/or dependence using ICD-9-CM or ICD-10-CM (outcome)] with the total number of medical cannabis dispensaries per square mile in a ZIP code as well as dispensary temporal and spatial lags (primary exposures). Other exposure covariates included alcohol outlet densities, manual labor and retail sales densities and ZIP code-level economic and demographic conditions.

FINDINGS

One additional dispensary per square mile was associated with a median risk ratio of 1.021 (95% credible interval 1.001, 1.041). Prior-year dispensary density did not appear to be associated with hospitalizations (median risk ratio = 1.006, 95% CrI = 0.986, 1.026). Higher median household income, higher unemployment, greater off-premises alcohol outlet density and lower on-premises alcohol outlet density and poverty were all associated with decreased ZIP code-level risk of cannabis abuse/dependence hospitalizations.

CONCLUSIONS

In California, USA, the increasing density of medical cannabis dispensaries appears to be positively associated with same-year but not next-year hospitalizations for cannabis use disorder.

Differences in Opinions About Marijuana Use and Prevalence of Use by State Legalization Status

OBJECTIVE

Beliefs about marijuana use and prevalence of use may be associated with the legalization status of the state of residence. We examined differences in views and rates of use of marijuana among residents in recreationally legal, medically legal, and nonlegal states.

METHODS

We surveyed a nationally representative online panel of US adults (N = 16,280) and stratified results by marijuana legalization status of states. We compared views of residents of recreational states on benefits and risks of marijuana use to residents in other states.

RESULTS

The response rate was 56.3% (n = 9003). Residents in recreationally legal states were more likely to believe marijuana could be beneficial for pain management (73% in recreationally legal states, 67% in medically legal states, 63% in nonlegal states; P value: <0.0001), provide relief from stress, anxiety or depression (52% in recreationally legal states, 47% in medically legal states, 46% in nonlegal states; P value: 0.01), and improve appetite (39% in recreationally legal states, 36% in medically legal states, 33% in nonlegal states; P value: <0.009). In addition, residents in recreational states were significantly more likely to believe that smoking 1 marijuana joint a day is somewhat or much safer than smoking 1 cigarette a day (40.8% in recreationally legal states, 39.1% in medically legal states, and 36.1% in nonlegal states; P value: <0.0001). Residents of recreationally and medically legal states were more likely to believe second-hand marijuana smoke was somewhat or much safer than second-hand tobacco smoke (38.3% in recreationally legal states, 38.3% in medically legal states, and 35.7% in nonlegal states; P value: 0.003). Past-year marijuana use in any form (20% in recreational, 14.1% in medical, 12% in nonlegal) and past-year marijuana use of multiple forms (11.1% in recreational, 6.1% in medical, 4.9% in nonlegal) were highest among residents of recreationally legal states. Overall, prevalence of past-year use of any form of marijuana use was more common among residents of recreationally legal states compared with other states (20.3%, confidence interval [CI] 19.5, 21.1 in recreationally legal states; 15.4%, CI 14.7, 16.2 in medically legal states; 11.9%, CI 11.2, 12.6 in nonlegal states).

CONCLUSIONS

Residents in recreationally legal states were most likely to believe marijuana has benefits, marijuana smoke is safer than tobacco smoke, and have the highest rate of marijuana use. This is cause for concern, given the tide of commercialization, growing number of high-potency cannabis products, and favorable media coverage promoting use for health problems.

Cannabis use, use frequency, and use disorder in large metropolitan, small metropolitan, and nonmetropolitan areas

BACKGROUND

Despite significant geographical heterogeneity of sociodemographic and clinical characteristics, little is known about potential differences in cannabis use behaviors in U.S. geographic areas. In this study, we examined cannabis use behaviors in large metropolitan, small metropolitan, and nonmetropolitan areas. We focused on interactions between geographic areas and health insurance status and medical cannabis laws (MCL).

METHODS

Data came from the 2015-2018 National Survey on Drug Use and Health (NSDUH; N = 171,766 adults; N = 36,175 cannabis users). Weighted chi-squares tests of independence and multivariable Poisson regression models were used to examine study questions.

RESULTS

Past-year use was highest in large metropolitan areas (16.08 %). Frequent use was highest among nonmetropolitan area users (48.67 %). Uninsured adults had a higher likelihood of past-year use (RRR = 1.21, 95 % CI = 1.14, 1.29) and frequent use (RRR = 1.27, 95 % CI = 1.14, 1.41), but a lower likelihood of cannabis use disorder (RRR = 0.77, 95 % CI = 0.66, 0.89). Uninsured adults in nonmetropolitan areas had a higher likelihood (RRR = 1.62, 95 % CI = 1.39, 1.88) of past-year use than insured nonmetropolitan area adults. MCL state residency was associated with a higher likelihood of frequent use among nonmetropolitan (RRR = 1.39, 95 % CI = 1.11, 1.74) and small metropolitan users (RRR = 1.30, 95 % CI = 1.15, 1.47). Cannabis use disorder likelihood did not vary by geographic area.

CONCLUSIONS

Lack of health insurance and MCL state residency are significant variables affecting cannabis use behaviors in small metropolitan and/or nonmetropolitan areas.

Replicating the Dimensional Structure of Cannabis Problems: A Taxometric Analysis

This study employed taxometric procedures to replicate a previous report of the dimensional structure of problems related to cannabis consumption. Method: Over 4,000 cannabis users completed an assessment of psychological, social, occupational, and physical harms (the Marijuana Problems Scale). Three taxometric procedures (MAMBAC, MAXEIG, and L-Mode) compared the current data to simulations with a base rate of problematic cannabis use derived from representative, large-scale data estimates. Results: All three procedures confirmed the continuous, dimensional nature of these cannabis problems and suggested no underlying taxon or category. Conclusions: Psychopathological disorders, including some substance use problems, have fit categorical models suggesting that they differ in kind (rather than intensity) from the behavior of the rest of the population. Cannabis problems, however, appeared to lie along a continuum with other forms of use. Given heightened awareness for the necessity of replication and a changing legal landscape for cannabis, a second look at the dimensionality of these problems seemed warranted. New data with a larger sample and different indices of problematic use confirmed the dimensionality of cannabis problems. This replication can inform predictions about the etiology, prevention, and treatment of cannabis use disorder. Researchers should expect cannabis problems to range along a continuum without categorical distinctions. Dividing users into groups of problematic and non-problematic users likely sacrifices meaningful variance. Harm reduction strategies likely can benefit all users rather than a targeted taxon with troubles. In addition, interventions will likely progress by small, incremental steps rather than dramatic, categorical jumps in progress.

Implications of Medical and Recreational Marijuana Laws for Neuroscience Research: a Review

Purpose of Review

Review of US medical and recreational marijuana laws (MML and RML), their effects on cannabis potency, prevalence of non-medical cannabis use and cannabis use disorder (CUD) in adolescents and adults, and implications for neuroscience research, given what is known about the relationship of cannabis to neurocognitive impairments and underlying brain functioning.

Recent Findings

Cannabis potency may be increasing faster in states with MML or RML than in other states. MML and RML have not impacted prevalence in adolescents but have consistently been shown to increase rates of adult non-medical use and CUD.

Summary

Recent neurocognitive or neuroimaging studies may be more impacted by cannabis than studies conducted when MML and RML were less common. Neurocognitive or neuroimaging studies conducted in MML or RML states should carefully test potential participants for recent cannabis use. More research is needed on cannabis and cognition in medical marijuana patients.

A preliminary risk prediction model for cannabis use disorder

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Substance use disorders are currently a major public health crisis in the US.

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The prevalence of cannabis use disorder is rising due to legalization of cannabis.

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This study built models to predict the risk of cannabis use disorder for a user.

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Risk factors include personality traits, impulsivity and initial smoking enjoyment.

The ongoing trend toward legalization of cannabis for medicinal/recreational purposes is expected to increase the prevalence of cannabis use disorder (CUD). Thus, it is imperative to be able to predict the quantitative risk of developing CUD for a cannabis user based on their personal risk factors. Yet no such model currently exists. In this study, we perform preliminary analysis toward building such a model. The data come from n = 94 regular cannabis users recruited from Albuquerque, New Mexico during 2007–2010. As the data are cross-sectional, we only consider risk factors that remain relatively stable over time. We apply statistical and machine learning classification techniques that allow n to be small relative to the number of predictors. We use predictive accuracy estimated using leave-one-out-cross-validation to evaluate model performance. The final model is a LASSO logistic regression model consisting of the following seven risk factors: age; level of enjoyment from initial cigarette smoking; total score on Impulsive Sensation-Seeking Scale questionnaire; score on cognitive instability factor of Barratt Impulsivity Scale questionnaire; and scores on neuroticism, openness, and conscientiousness personality traits of Neuroticism, Extraversion, and Openness inventory. This model has an overall accuracy of 0.66 and the area under its receiver operating characteristic curve is 0.65. In summary, a preliminary relative risk model for predicting the quantitative risk of CUD is developed. It can be employed to identify users at high risk of CUD who may be provided with early intervention.

Preinjury Use of Marijuana and Outcomes in Trauma Patients

BACKGROUND

Recent studies have examined the effects of marijuana in various populations; however, there has been limited research on the effect of marijuana use in severely injured trauma patients. We hypothesized that preinjury use of marijuana would be associated with improved outcomes in severely injured trauma patients.

METHODS

All adult (18+ y) level I and level II trauma activations who presented to two large regional trauma centers between 2014 and 2018 were reviewed. Delta-9-tetrahydrocannabinol (THC)- indicated absence of drugs confirmed by testing and as THC + confirmed THC without another drug present.

RESULTS

Of the 4849 patients included, 1373 (28.3%) were THC+. The THC + cohort was younger, had more males, and was more likely to be injured by penetrating mechanism (P < 0.001 for all) than THC-. THC + patients had shorter median length of stay (LOS) (P < 0.001) and intensive care unit LOS (P < 0.001). Mortality rate was lower in the THC + group (4.3% versus 7.6%, P < 0.001), but not in multivariate analysis. THC + patients with traumatic brain injury had shorter hospital LOS (P = 0.025) and shorter ventilator days (P = 0.033) than THC- patients. In patients with Injury Severity Score ≥16, THC + patients had significantly lower intensive care unit LOS (P = 0.009) and mortality (19.3% versus 25.0% P = 0.038) than drug-negative patients.

CONCLUSIONS

Although preinjury use of marijuana does not improve survival in trauma patients, it may provide some improvement in outcomes in patients with traumatic brain injury and those that are more severely injured (Injury Severity Score ≥16). The mechanism behind this finding needs further evaluation.

The Effect of Marijuana Legalization on the Trajectories of Hard Drug–Related Hospitalizations: A Growth Curve Analysis of the County-Level State Inpatient Database in Washington, 2009–2015

Two antithetical arguments have raised controversies over the effect of recreational marijuana legalization on hard drug use. The gateway perspective posits that marijuana use diffuses hard drug use; however, recent studies argue that marijuana legalization displaces hard drug use. This study examines these conflicting arguments by investigating temporal patterns of hard drug–related hospitalizations (HDHs) before and after marijuana legalization. Using county-level State Inpatient Database data from Washington State for the years 2009–2015, along with other federal data sources, this study assesses temporal changes in HDH using growth curve modeling. Initial findings show support for the displacement perspective, though controlling for other county-level factors (education and economic change) indicates that the legalization of recreational marijuana may be a gateway toward harder drugs. Considering the economic situation of the United States during the study period, this study concludes that marijuana legalization functioned as a gateway toward increased hard drug use.

Medical marijuana and workers' compensation claiming

We study the effect of state medical marijuana laws (MMLs) on workers' compensation (WC) claiming among adults. Medical marijuana is plausibly related to WC claiming by allowing improved symptom management, and thus reduced need for the benefit, among injured or ill workers. We use data on claiming drawn from the Annual Social and Economic supplement to the Current Population Survey over the period 1989 to 2012, coupled with a differences-in-differences design to provide the first evidence on this relationship. Our estimates show that, post MML, WC claiming declines, both the propensity to claim and the level of income from WC. These findings suggest that medical marijuana can allow workers to better manage symptoms associated with workplace injuries and illnesses and, in turn, reduce need for WC. However, the reductions in WC claiming post MML are very modest in size.

Guidelines for public health and safety metrics to evaluate the potential harms and benefits of cannabis regulation in Canada

ISSUES

Canada recently introduced a public health-based regulatory framework for non-medical cannabis. This review sought to identify a comprehensive set of indicators to evaluate the public health and safety impact of cannabis regulation in Canada, and to explore the ways in which these indicators may be expected to change in the era of legal non-medical cannabis.

APPROACH

Five scientific databases were searched to compile a list of cannabis-related issues of interest to public health and safety. A set of indicators was developed based on topics and themes that emerged. Preliminary evidence from other jurisdictions in the USA and Canada that have legalised medical and/or non-medical cannabis (e.g. Colorado, Washington) was summarised for each indicator, wherever possible.

KEY FINDINGS

In total, 28 indicators were identified under five broad themes: public safety; cannabis use trends; other substance use trends; cardiovascular and respiratory health; and mental health and cognition. Preliminary trends from other legalised jurisdictions reveal little consensus regarding the effect of cannabis legalisation on public health and safety harms and an emerging body of evidence to support potential benefits (e.g. reductions in opioid use and overdose).

IMPLICATIONS

In addition to indicators of commonly discussed challenges (e.g. cannabis-related hospitalisations, cannabis-impaired driving), this review led to the recommendation of several indicators to monitor for possible public health and safety improvements.

CONCLUSION

In preparing a comprehensive public health and safety monitoring and evaluation system for cannabis regulation, this review underscores the importance of not only measuring the possible risks but also the potential benefits.

Sex, marijuana and baby booms

We study the behavioral changes caused by marijuana use on sexual activity, contraception, and birth counts by applying a differences-in-differences approach that exploits the variation in timing of the introduction of medical marijuana laws (MMLs) among states. We find that MMLs cause an increase in sexual activity, a reduction in contraceptive use conditional on having sex, and an increase in number of births. There is also suggestive evidence on temporary increases in the state-year gonorrhea rate. These changes may be attributed to behavioral responses including increased attention to the immediate hedonic effects of sexual contact, increased sexual frequency, as well as delayed discounting and ignoring the future costs associated with sex. Our findings on births suggest that behavioral factors can counteract the physiological changes from marijuana use that tend to decrease fertility. Our findings are robust to a broad set of tests.

Trends in Cannabis Treatment Admissions in Adolescents/Young Adults: Analysis of TEDS-A 1992 to 2016

OBJECTIVES

This study aims to evaluate changes in cannabis use patterns, referral sources, and admissions in adolescents and young adults (YAs). As the United States increasingly moves toward liberalization of cannabis laws, it is critical to have baseline information of use patterns in this population.

METHODS

Data were drawn from Treatment Episode Data Set-Admissions (TEDS-A) for adolescents (12-17 years) and young adults (18-24 years) entering treatment from 1992 to 2016 for primary cannabis use (N = 3,794,213). Rao-Scott chi-square tests were used to test for significant changes in proportions of individuals admitted to treatment for primary cannabis use and between 4-year increments from 1992 to 2016 (N = 1,052,724). Logistic regression assessed odds of admissions for primary cannabis use versus other substances.

RESULTS

Treatment admissions for cannabis among adolescents/YAs rose 3-fold from 1992 (49,996) to 1996 (125,858). The majority of referrals came from the criminal justice system (56%). Cannabis is increasingly the sole substance of use, with polysubstance use decreasing from 89% in 1992 to 59% in 2016. While alcohol-related treatment admissions were most common in 1992, admissions for treatment of cannabis use (followed by heroin and alcohol) were highest (38%) by 2016. Being an adolescent (odds ratio [OR] 3.1, 95% confidence interval [CI] 3.1-3.2), non-Hispanic black (OR 6.2, 95% CI 6.2-6.3), male (female OR 0.6, 95% CI 0.6-0.6) with co-occurring alcohol use (OR 25.9, 95% CI 25.7-26.1) was associated with admission for treatment of primary cannabis use as compared with other substances.

CONCLUSIONS

Public health efforts will be needed to ensure ongoing access and referral to treatment as the legal status of cannabis continues to change. Prevention and treatment efforts should target co-occurring alcohol and cannabis use.

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.

Fatal crashes in the 5 years after recreational marijuana legalization in Colorado and Washington

Colorado and Washington legalized recreational marijuana in 2012, but the effects of legalization on motor vehicle crashes remains unknown. Using Fatality Analysis Reporting System data, we performed difference-in-differences (DD) analyses comparing changes in fatal crash rates in Washington, Colorado and nine control states with stable anti-marijuana laws or medical marijuana laws over the five years before and after recreational marijuana legalization. In separate analyses, we evaluated fatal crash rates before and after commercial marijuana dispensaries began operating in 2014. In the five years after legalization, fatal crash rates increased more in Colorado and Washington than would be expected had they continued to parallel crash rates in the control states (+1.2 crashes/billion vehicle miles traveled, CI: -0.6 to 2.1, p = 0.087), but not significantly so. The effect was more pronounced and statistically significant after the opening of commercial dispensaries (+1.8 crashes/billion vehicle miles traveled, CI: +0.4 to +3.7, p = 0.020). These data provide evidence of the need for policy strategies to mitigate increasing crash risks as more states legalize recreational marijuana.

The Impact of Medical Marijuana Laws and Dispensaries on Self-Reported Health

Growing evidence suggests that medical marijuana laws have harm reduction effects across a variety of outcomes related to risky health behaviors. This study investigates the impact of medical marijuana laws on self-reported health using data from the Behavioral Risk Factor Surveillance System from 1993 to 2013. In our analyses we separately identify the effect of a medical marijuana law and the impact of subsequent active and legally protected dispensaries. Our main results show surprisingly limited improvements in self-reported health after the legalization of medical marijuana and legally protected dispensaries. Subsample analyses reveal strong improvements in health among non-white individuals, those reporting chronic pain, and those with a high school degree, driven predominately by whether or not the state had active and legally protected dispensaries. We also complement the analysis by evaluating the impact on risky health behaviors and find that the aforementioned demographic groups experience large reductions in alcohol consumption after the implementation of a medical marijuana law.

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.

Age Differences in Daily and Nondaily Cannabis Use in the United States, 2002-2014

OBJECTIVE

Adult cannabis use has increased in the United States since 2002, particularly after 2007, contrasting with stable/declining trends among youth. We investigated whether specific age groups disproportionately contributed to changes in daily and nondaily cannabis use trends.

METHOD

Participants ages 12 and older (N = 722,653) from the 2002-2014 National Survey on Drug Use and Health reported past-year cannabis use frequency (i.e., daily = ≥300 days/year; nondaily = 1-299 days/year; none). Multinomial logistic regression was used to model change in past-year daily and nondaily cannabis use prevalence by age group (i.e., 12-17, 18-25, 26-34, 35-49, 50-64, ≥65), before and after 2007. Multinomial logistic regressions estimated change in relative odds of cannabis use frequency over time by age, adjusting for other sociodemographics.

RESULTS

Daily cannabis use prevalence decreased in ages 12-17 before 2007 and increased significantly across adult age categories only after 2007. Increases did not differ significantly across adult ages 18-64 and ranged between 1 and 2 percentage points. Nondaily cannabis use decreased among respondents ages 12-25 and 35-49 before 2007 and increased across adult age categories after 2007, particularly among adults 26-34 (i.e., 4.5 percentage points). Adjusted odds of daily versus nondaily cannabis use increased after 2007 for ages 12-64.

CONCLUSIONS

Increases in daily and nondaily cannabis use prevalence after 2007 were specific to adult age groups in the context of increasingly permissive cannabis legislation, attitudes, and lower risk perception. Although any cannabis use may be decreasing among teens, relative odds of more frequent use among users increased in ages 12-64 since 2007. Studies should assess not only any cannabis use, but also frequency of use, to target prevention efforts of adverse effects of cannabis that are especially likely among frequent users.

State marijuana laws and opioid overdose mortality

Background

The opioid epidemic in the United States is a national public health crisis. In recent years, marijuana legalization has been increasingly adopted by state governments as a policy intervention to control the opioid epidemic under the premise that marijuana and opioids are substitutive substances. The purpose of this systematic review is to synthesize the empirical evidence regarding the impact of state marijuana laws on opioid overdose mortality and other opioid-related health outcomes.

Method

A comprehensive search of the research literature in 18 bibliographic databases returned 6640 records, with 5601 abstracts reviewed, 29 full text articles screened for eligibility, and 16 eligible studies included in the systematic review. Comprehensive Meta-Analysis software was used to generate summary estimates, forest plots, funnel plots, and heterogeneity statistics.

Results

Of the 16 eligible studies, 4 assessed the association of state marijuana law status with opioid overdose mortality, 7 with prescription opioids dispensed, and the remaining with nonmedical use and opioid-related hospitalizations. Random effects modeling based on pooled data revealed that legalizing marijuana for medical use was associated with a statistically non-significant 8% reduction in opioid overdose mortality (95% confidence interval: − 0.21 to 0.04; p = 0.201) and a 7% reduction in prescription opioids dispensed (95% confidence interval: − 0.13 to − 0.01; p = 0.017). Legalizing marijuana for recreational use was associated with an additional 7% reduction in opioid overdose mortality in Colorado and 6% reduction in opioid prescriptions among fee-for-service Medicaid and managed care enrollees.

Conclusions

Legalizing marijuana might contribute to a modest reduction in opioid prescriptions. Evidence about the effect of marijuana legalization on opioid overdose mortality is inconsistent and inconclusive. If any, the effectiveness of state marijuana laws in reducing opioid overdose mortality appears to be rather small and limited to states with operational marijuana dispensaries. It remains unclear whether the presumed benefit of legalizing marijuana in reducing opioid-related harms outweighs the policy’s externalities, such as its impact on mental health and traffic safety.

Medical marijuana laws are associated with increases in substance use treatment admissions by pregnant women

BACKGROUND AND AIMS

Between 2002 and 2014, past-month marijuana use among pregnant women in the United States increased 62%, nearly twice the growth of the general population. This growth coincides with the proliferation of state medical marijuana laws (MMLs) authorizing physicians to recommend marijuana for approved conditions. We estimated the association between MMLs and substance use treatment utilization among pregnant and non-pregnant women of reproductive age. We also examined whether the association varied across MML provisions, age groups and treatment referral sources to clarify potential pathways.

DESIGN

Nation-wide administrative data from the 2002-14 Treatment Episodes Data Set Admissions, and a difference-in-differences design that exploited the staggered implementation of MMLs to compare changes in outcomes before and after implementation between MML and non-MML states.

SETTING

Twenty-one MML and 27 non-MML US states.

PARTICIPANTS

Pregnant and non-pregnant women aged 12-49 admitted to publicly funded specialty substance use treatment facilities.

MEASUREMENTS

The primary outcome variable was the number of treatment admissions per 100 000 women aged 12-49, aggregated at the state-year level (n = 606). Admissions for marijuana, alcohol, cocaine and opioids were considered. The primary independent variable was an indicator of MML implementation in a state.

FINDINGS

Among pregnant women, the rate of marijuana treatment admissions increased by 4.69 [95% confidence interval (CI) = 1.32, 8.06] in MML states relative to non-MML states. This growth was accompanied by increases in treatment admissions involving alcohol (β = 3.19; 95% CI = 0.97, 5.410 and cocaine (β = 2.56; 95% CI = 0.34, 4.79), was specific to adults (β = 5.50; 95% CI = 1.52, 9.47) and was largest in states granting legal protection for marijuana dispensaries (β = 6.37; 95% CI = -0.97, 13.70). There was no statistically significant association between MMLs and treatment admissions by non-pregnant women.

CONCLUSIONS

Medical marijuana law implementation in US states has been associated with greater substance use treatment utilization by pregnant adult women, especially in states with legally protected dispensaries.

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

OBJECTIVES

To examine the effect of cannabis policy liberalisation (decriminalisation and legalisation) levels of use in adolescents and young adults.

DESIGN

Systematic review and meta-analysis.

INCLUSION CRITERIA

Included studies were conducted among individuals younger than 25 years and quantitatively assessing consequences of cannabis policy change. We excluded articles: (A) exclusively based on participants older than 25 years; (B) only reporting changes in perceptions of cannabis use; (C) not including at least two measures of cannabis use; (D) not including quantitative data; and (E) reviews, letters, opinions and policy papers. PubMed, PsycINFO, Embase and Web of Science were searched through 1 March 2018.

DATA EXTRACTION AND SYNTHESIS

Two independent readers reviewed the eligibility of titles and abstracts and read eligible articles, and four authors assessed the risk of bias (Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies). Extracted data were meta-analysed. The protocol was registered with PROSPERO.

RESULTS

3438 records were identified via search terms and four via citation lists; 2312 were retained after removal of duplicates, 99 were assessed for eligibility and 41 were included in our systematic review. 13 articles examined cannabis decriminalisation, 20 examined legalisation for medical purposes and 8 examined legalisation for recreational purposes. Findings regarding the consequences of cannabis decriminalisation or legalisation for medical purposes were too heterogeneous to be meta-analysed. Our systematic review and meta-analysis suggest a small increase in cannabis use among adolescents and young adults following legalisation of cannabis for recreational purposes (standardised mean difference of 0.03, 95% CI -0.01 to -0.07). Nevertheless, studies characterised by a very low/low risk of bias showed no evidence of changes in cannabis use following policy modifications.

CONCLUSIONS

Cannabis policy liberalisation does not appear to result in significant changes in youths' use, with the possible exception of legalisation for recreational purposes that requires monitoring.

TRIAL REGISTRATION NUMBER

CRD42018083950.

Correct knowledge of medical cannabis legal status in one's own state: Differences between adolescents and adults in the United States, 2004-2013

BACKGROUND

Studies have found age-specific effects of medical cannabis laws (MCLs), particularly affecting adult cannabis use but not adolescent use. We examined whether age differences in MCL knowledge are in accordance with age differences in MCL effects on cannabis use.

METHODS

Data from the 2004-2013 repeated cross-sectional National Surveys on Drug Use and Health included people ages 12 and older in the United States. State-aggregated MCL knowledge was the proportion of people that correctly identified living in a state that did not allow medical cannabis prior to MCL enactment, or that allowed medical cannabis after MCL enactment. We regressed state-aggregated MCL knowledge on time-varying MCL enactment (i.e., no MCL by 2015, before MCL, after MCL), testing associations by age strata (12-17, 18-25, 26+), open dispensary status, and adjusting for time and state-level demographics.

RESULTS

Model-based MCL knowledge was significantly lower among adolescents than adults; after enactment, 36.8% of ages 12-17, 48.8% of ages 18-25, and 45.4% of ages 26+ were aware of their state's MCL status. Correct MCL status knowledge decreased across all age groups after MCL enactment (i.e., low knowledge of MCL changes at the time they occurred). Open cannabis dispensaries significantly increased correct MCL knowledge, with a 7.7-point increase for adolescents and a 17.5-point increase for adults 26 + .

CONCLUSIONS

Lower MCL knowledge among adolescents than adults was in accordance with MCL effects on cannabis use previously observed among adults only. Studies should assess whether MCL knowledge is a consequence or predictor of individual-level cannabis use across age groups.

Risks and Benefits of Marijuana Use: A National Survey of U.S. Adults

BACKGROUND

Despite insufficient evidence regarding its risks and benefits, marijuana is increasingly available and is aggressively marketed to the public.

OBJECTIVE

To understand the public's views on the risks and benefits of marijuana use.

DESIGN

Probability-based online survey.

SETTING

United States, 2017.

PARTICIPANTS

16 280 U.S. adults.

MEASUREMENTS

Proportion of U.S. adults who agreed with a statement.

RESULTS

The response rate was 55.3% (n = 9003). Approximately 14.6% of U.S. adults reported using marijuana in the past year. About 81% of U.S. adults believe marijuana has at least 1 benefit, whereas 17% believe it has no benefit. The most common benefit cited was pain management (66%), followed by treatment of diseases, such as epilepsy and multiple sclerosis (48%), and relief from anxiety, stress, and depression (47%). About 91% of U.S. adults believe marijuana has at least 1 risk, whereas 9% believe it has no risks. The most common risk identified by the public was legal problems (51.8%), followed by addiction (50%) and impaired memory (42%). Among U.S. adults, 29.2% agree that smoking marijuana prevents health problems. About 18% believe exposure to secondhand marijuana smoke is somewhat or completely safe for adults, whereas 7.6% indicated that it is somewhat or completely safe for children. Of the respondents, 7.3% agree that marijuana use is somewhat or completely safe during pregnancy. About 22.4% of U.S. adults believe that marijuana is not at all addictive.

LIMITATION

Wording of the questions may have affected interpretation.

CONCLUSION

Americans' view of marijuana use is more favorable than existing evidence supports.

PRIMARY FUNDING SOURCE

National Heart, Lung, and Blood Institute.

Medical marijuana laws and workplace fatalities in the United States

AIMS

The aim of this research was to determine the association between legalizing medical marijuana and workplace fatalities.

DESIGN

Repeated cross-sectional data on workplace fatalities at the state-year level were analyzed using a multivariate Poisson regression.

SETTING

To date, 29 states and the District of Columbia have legalized the use of marijuana for medicinal purposes. Although there is increasing concern that legalizing medical marijuana will make workplaces more dangerous, little is known about the relationship between medical marijuana laws (MMLs) and workplace fatalities.

PARTICIPANTS

All 50 states and the District of Columbia for the period 1992-2015.

MEASUREMENTS

Workplace fatalities by state and year were obtained from the Bureau of Labor Statistics. Regression models were adjusted for state demographics, the unemployment rate, state fixed effects, and year fixed effects.

FINDINGS

Legalizing medical marijuana was associated with a 19.5% reduction in the expected number of workplace fatalities among workers aged 25-44 (incident rate ratio [IRR], 0.805; 95% CI, .662-.979). The association between legalizing medical marijuana and workplace fatalities among workers aged 16-24, although negative, was not statistically significant at conventional levels. The association between legalizing medical marijuana and workplace fatalities among workers aged 25-44 grew stronger over time. Five years after coming into effect, MMLs were associated with a 33.7% reduction in the expected number of workplace fatalities (IRR, 0.663; 95% CI, .482-.912). MMLs that listed pain as a qualifying condition or allowed collective cultivation were associated with larger reductions in fatalities among workers aged 25-44 than those that did not.

CONCLUSIONS

The results provide evidence that legalizing medical marijuana improved workplace safety for workers aged 25-44. Further investigation is required to determine whether this result is attributable to reductions in the consumption of alcohol and other substances that impair cognitive function, memory, and motor skills.

Medical marijuana laws and adolescent marijuana use in the United States: a systematic review and meta-analysis

AIMS

To conduct a systematic review and meta-analysis of studies in order to estimate the effect of US medical marijuana laws (MMLs) on past-month marijuana use prevalence among adolescents.

METHODS

A total of 2999 papers from 17 literature sources were screened systematically. Eleven studies, developed from four ongoing large national surveys, were meta-analyzed. Estimates of MML effects on any past-month marijuana use prevalence from included studies were obtained from comparisons of pre-post MML changes in MML states to changes in non-MML states over comparable time-periods. These estimates were standardized and entered into a meta-analysis model with fixed-effects for each study. Heterogeneity among the study estimates by national data survey was tested with an omnibus F-test. Estimates of effects on additional marijuana outcomes, of MML provisions (e.g. dispensaries) and among demographic subgroups were abstracted and summarized. Key methodological and modeling characteristics were also described. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed.

RESULTS

None of the 11 studies found significant estimates of pre-post MML changes compared with contemporaneous changes in non-MML states for marijuana use prevalence among adolescents. The meta-analysis yielded a non-significant pooled estimate (standardized mean difference) of -0.003 (95% confidence interval = -0.012, +0.007). Four studies compared MML with non-MML states on pre-MML differences and all found higher rates of past-month marijuana use in MML states pre-MML passage. Additional tests of specific MML provisions, of MML effects on additional marijuana outcomes and among subgroups generally yielded non-significant results, although limited heterogeneity may warrant further study.

CONCLUSIONS

Synthesis of the current evidence does not support the hypothesis that US medical marijuana laws (MMLs) until 2014 have led to increases in adolescent marijuana use prevalence. Limited heterogeneity exists among estimates of effects of MMLs on other patterns of marijuana use, of effects within particular population subgroups and of effects of specific MML provisions.

Medical Marijuana and Marijuana Legalization

State-level marijuana liberalization policies have been evolving for the past five decades, and yet the overall scientific evidence of the impact of these policies is widely believed to be inconclusive. In this review we summarize some of the key limitations of the studies evaluating the effects of decriminalization and medical marijuana laws on marijuana use, highlighting their inconsistencies in terms of the heterogeneity of policies, the timing of the evaluations, and the measures of use being considered. We suggest that the heterogeneity in the responsiveness of different populations to particular laws is important for interpreting the mixed findings from the literature, and we highlight the limitations of the existing literature in providing clear insights into the probable effects of marijuana legalization.

Do medical marijuana laws reduce addictions and deaths related to pain killers?

Recent work finds that medical marijuana laws reduce the daily doses filled for opioid analgesics among Medicare Part-D and Medicaid enrollees, as well as population-wide opioid overdose deaths. We replicate the result for opioid overdose deaths and explore the potential mechanism. The key feature of a medical marijuana law that facilitates a reduction in overdose death rates is a relatively liberal allowance for dispensaries. As states have become more stringent in their regulation of dispensaries, the protective value generally has fallen. These findings suggest that broader access to medical marijuana facilitates substitution of marijuana for powerful and addictive opioids.

Medical Marijuana Laws and Marijuana Use Among U.S. Adolescents: Evidence From Michigan Youth Risk Behavior Surveillance Data

Research findings are inconsistent regarding a positive association between the passage of state medical marijuana laws (MML) and adolescent access and use marijuana. We utilized a novel analytical approach to examine this issue with multi-year data from the 1997–2013 Youth Risk Behavior Surveillance System (YRBSS) of the State of Michigan. After controlling for the historically declining trend in marijuana use prior to the passages of MML in Michigan, we found that marijuana use among adolescents had increased subsequent to the passage of state MML. Study findings suggest the need for considering the increased risk of marijuana use among adolescents as the number of states with laws permitting marijuana use is increasing.

US Epidemiology of Cannabis Use and Associated Problems

This review provides an overview of the changing US epidemiology of cannabis use and associated problems. Adults and adolescents increasingly view cannabis as harmless, and some can use cannabis without harm. However, potential problems include harms from prenatal exposure and unintentional childhood exposure; decline in educational or occupational functioning after early adolescent use, and in adulthood, impaired driving and vehicle crashes; cannabis use disorders (CUD), cannabis withdrawal, and psychiatric comorbidity. Evidence suggests national increases in cannabis potency, prenatal and unintentional childhood exposure; and in adults, increased use, CUD, cannabis-related emergency room visits, and fatal vehicle crashes. Twenty-nine states have medical marijuana laws (MMLs) and of these, 8 have recreational marijuana laws (RMLs). Many studies indicate that MMLs or their specific provisions did not increase adolescent cannabis use. However, the more limited literature suggests that MMLs have led to increased cannabis potency, unintentional childhood exposures, adult cannabis use, and adult CUD. Ecological-level studies suggest that MMLs have led to substitution of cannabis for opioids, and also possibly for psychiatric medications. Much remains to be determined about cannabis trends and the role of MMLs and RMLs in these trends. The public, health professionals, and policy makers would benefit from education about the risks of cannabis use, the increases in such risks, and the role of marijuana laws in these increases.

Effects of the 2009 Medical Cannabinoid Legalization Policy on Hospital Use for Cannabinoid Dependency and Persistent Vomiting

BACKGROUND & AIMS

In 2009, the U.S. Department of Justice issued a memo stating that it would not prosecute users and sellers who complied with the state laws allowing for medical use of marijuana. There are growing concerns about legalization of marijuana use and its related public health effects. We performed an interrupted time series analysis to evaluate these effects.

METHODS

We collected a representative sample of hospital discharge data from the Healthcare Cost and Utilization Project, from January 1993 to December 2014. We divided the data in to 3 groups: the prelegalization period (1993-2008), the legalization period (2009), and the postlegalization period (2010-2014). The disease variables were International Classification of Disease-Ninth Revision-Clinical Modification 304.30 cannabinoid dependency unspecified (CDU), 536.2 persistent vomiting, and an aggregate of CDU and persistent vomiting. We performed interrupted time series and Poisson-Gamma regression analysis to calculate each year's incidence rate of unspecified and persistent vomiting and CDU per 100,000 hospital discharges. CDU, persistent vomiting, and aggregate of CDU and persistent vomiting were modeled separately to estimate average incidence rate ratio and 95% confidence interval for each study phase.

RESULTS

We observed an increasing trend of CDU or an aggregate of CDU and persistent vomiting during the prelegalization period. The legalization of marijuana significantly increased the incidence rate during the legalization period (by 17.9%) and the yearly average increase in rate by 6% after policy implementation, compared to the prelegalization period. The increase in rate of persistent vomiting after policy implementation increased significantly (by about 8%), although there were no significant trends in increase prior to or during marijuana legalization in 2009.

CONCLUSIONS

In an interrupted time series analysis of before, during, and after medical marijuana legalization, we estimated levels and rate changes in CDU and persistent vomiting. We found persistent increases in rates of CDU and persistent vomiting during and after legalization of marijuana.

Mapping medical marijuana: state laws regulating patients, product safety, supply chains and dispensaries, 2017

AIMS

(1) To describe open source legal data sets, created for research use, that capture the key provisions of US state medical marijuana laws. The data document how state lawmakers have regulated a medicine that remains, under federal law, a Schedule I illegal drug with no legitimate medical use. (2) To demonstrate the variability that exists across states in rules governing patient access, product safety and dispensary practice.

METHODS

Two legal researchers collected and coded state laws governing marijuana patients, product safety and dispensaries in effect on 1 February 2017, creating three empirical legal data sets. We used summary tables to identify the variation in specific statutory provisions specified in each state's medical marijuana law as it existed on 1 February 2017. We compared aspects of these laws to the traditional Federal approach to regulating medicine. Full data sets, codebooks and protocols are available through the Prescription Drug Abuse Policy System (http://www.pdaps.org/; Archived at http://www.webcitation.org/6qv5CZNaZ on 2 June 2017).

RESULTS

Twenty-eight states (including the District of Columbia) have authorized medical marijuana. Twenty-seven specify qualifying diseases, which differ across states. All states protect patient privacy; only 14 protect patients against discrimination. Eighteen states have mandatory product safety testing before any sale. While the majority have package/label regulations, states have a wide range of specific requirements. Most regulate dispensaries (25 states), with considerable variation in specific provisions such as permitted product supply sources number of dispensaries per state and restricting proximity to various types of location.

CONCLUSIONS

The federal ban in the United States on marijuana has resulted in a patchwork of regulatory strategies that are not uniformly consistent with the approach usually taken by the Federal government and whose effectiveness remains unknown.

Cannabis use, attitudes, and legal status in the U.S.: A review

Cannabis is widely used among adolescents and adults. In the U.S., marijuana laws have been changing, and Americans increasingly favor legalizing cannabis for medical and recreational uses. While some can use cannabis without harm, others experience adverse consequences. The objective of this review is to summarize information on the legal status of cannabis, perceptions regarding cannabis, prevalence and time trends in use and related adverse consequences, and evidence on the relationship of state medical (MML) and recreational (RML) marijuana laws to use and attitudes. Twenty-nine states now have MMLs, and eight of these have RMLs. Since the early 2000s, adult and adolescent perception of cannabis use as risky has decreased. Over the same time, the prevalence of adolescent cannabis use has changed little. However, adult cannabis use, disorders, and related consequences have increased. Multiple nationally representative studies indicate that MMLs have had little effect on cannabis use among adolescents. However, while MML effects have been less studied in adults, available evidence suggests that MMLs increase use and cannabis use disorders in adults. While data are not yet available to evaluate the effect of RMLs, they are likely to lower price, increase availability, and thereby increase cannabis use. More permissive marijuana laws may accomplish social justice aims (e.g., reduce racial disparities in law enforcement) and generate tax revenues. However, such laws may increase cannabis-related adverse health and psychosocial consequences by increasing the population of users. Dissemination of balanced information about the potential health harms of cannabis use is needed.

Changes in undergraduates' marijuana, heavy alcohol and cigarette use following legalization of recreational marijuana use in Oregon

BACKGROUND AND AIMS

Recreational marijuana legalization (RML) went into effect in Oregon in July 2015. RML is expected to influence marijuana use by adolescents and young adults in particular, and by those with a propensity for substance use. We sought to quantify changes in rates of marijuana use among college students in Oregon from pre- to post-RML relative to college students in other states across the same time period.

DESIGN

Repeated cross-sectional survey data from the 2012-16 administrations of the Healthy Minds Study.

SETTING

Seven 4-year universities in the United States.

PARTICIPANTS

There were 10 924 undergraduate participants. One large public Oregon university participated in 2014 and 2016 (n = 588 and 1115, respectively); six universities in US states where recreational marijuana use was illegal participated both in 2016 and at least once between 2012 and 2015.

MEASUREMENTS

Self-reported marijuana use in the past 30 days (yes/no) was regressed on time (pre/post 2015), exposure to RML (i.e. Oregon students in 2016) and covariates using mixed-effects logistic regression. Moderation of RML effects by recent heavy alcohol use was examined.

FINDINGS

Rates of marijuana use increased from pre- to post-2015 at six of the seven universities, a trend that was significant overall. Increases in rates of marijuana use were significantly greater in Oregon than in comparison institutions, but only among students reporting recent heavy alcohol use.

CONCLUSIONS

Rates of Oregon college students' marijuana use increased (relative to that of students in other states) following recreational marijuana legislation in 2015, but only for those who reported recent heavy use of alcohol. Such alcohol misuse may be a proxy for vulnerabilities to substance use or lack of prohibitions (e.g. cultural) against it.

Structural barriers in access to medical marijuana in the USA-a systematic review protocol

BACKGROUND

There are 43 state medical marijuana programs in the USA, yet limited evidence is available on the demographic characteristics of the patient population accessing these programs. Moreover, insights into the social and structural barriers that inform patients' success in accessing medical marijuana are limited. A current gap in the scientific literature exists regarding generalizable data on the social, cultural, and structural mechanisms that hinder access to medical marijuana among qualifying patients. The goal of this systematic review, therefore, is to identify the aforementioned mechanisms that inform disparities in access to medical marijuana in the USA.

METHODS

This scoping review protocol outlines the proposed study design for the systematic review and evaluation of peer-reviewed scientific literature on structural barriers to medical marijuana access. The protocol follows the guidelines set forth by the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) checklist.

DISCUSSION

The overarching goal of this study is to rigorously evaluate the existing peer-reviewed data on access to medical marijuana in the USA. Income, ethnic background, stigma, and physician preferences have been posited as the primary structural barriers influencing medical marijuana patient population demographics in the USA. Identification of structural barriers to accessing medical marijuana provides a framework for future policies and programs. Evidence-based policies and programs for increasing medical marijuana access help minimize the disparity of access among qualifying patients.