A reexamination of medical marijuana policies in relation to suicide risk

Association Between Marijuana Laws and Suicide Among 12- to 25-Year-Olds in the United States From 2000 to 2019

OBJECTIVE

Cannabis use is associated with suicide-related outcomes in both adolescents and adults, and may be increasing amid shifting cannabis policies. However, little is known about the impact of medical marijuana legalization (MML) and recreational marijuana legalization (RML) policies on youth suicide. Using 20 years of national data, we examined associations between MML, RML, and suicide-related mortality among US individuals aged 12 to 25 years, and assessed whether they varied based on age and sex.

METHOD

Suicide deaths (N = 113,512) from the 2000-2019 National Vital Statistics System Multiple Cause of Death files for age groups 12 to 13, 14 to 16, 17 to 19, 20 to 22, and 23 to 25 years were examined in relation to time-varying cannabis law status using a staggered adoption difference-in-difference (DiD) approach with a negative binomial regression to determine associations between MML, RML, and suicide rates, controlling for individual- and state-level covariates and accounting for the varying effective dates of MML and RML by state.

RESULTS

The overall unadjusted annual suicide rate was 10.93/100,000, varying from 9.76 (states without marijuana laws (ML)) to 12.78 (MML states) to 16.68 (RML states). In multivariable analysis, both MML (incidence rate ratio [IRR] = 1.10, 95% CI: 1.05-1.15) and RML (IRR = 1.16, 95% CI: 1.06-1.27) were associated with higher suicide rates among female youth compared to those in states without ML. Youth aged 14 to 16 years had higher rates of suicide in states with RML compared to states with MML (IRR = 1.14, 95% CI: 1.00-1.30) and states without ML (IRR = 1.09, 95% CI: 1.00-1.20). Findings were consistent across sensitivity analyses.

CONCLUSION

MML and RML were associated with increased suicide-related mortality in female youth and 14- to- 16-year-old individuals of both sexes. Mechanisms through which cannabis policies are related to increased youth suicide warrant further study and should inform legislative reform.

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.

The highs and the lows: Recreational marijuana laws and mental health treatment

Recreational marijuana laws (RMLs) continue to grow in popularity, but the effects on mental health treatment are unclear. This paper uses an event-study within a difference-in-differences framework to study the short-run impact of state RMLs on admissions into mental health treatment facilities. The results indicate that shortly after a state adopts an RML, they experience a decrease in the average number of mental health treatment admissions. The findings are driven by white, Black, and Medicaid-funded admissions and are consistent for both male and female admissions. The results are robust to alternative specifications and sensitivity analysis.

The impact of recreational cannabis markets on motor vehicle accident, suicide, and opioid overdose fatalities

In the U.S., an increasing number of states are legalizing regulated commercial markets for recreational cannabis, which allows private industry to produce, distribute, and sell marijuana to those 21 and older. The health impacts of these markets are not fully understood. Preliminary evidence suggests recreational markets may be associated with increased use among adults, which indicates there may be downstream health impacts on outcomes related to cannabis use. Three causes of death that are linked to cannabis use are motor vehicle accidents, suicide, and opioid overdose. Drawing on data from U.S. death certificates from 2009 to 2019, we conducted a difference-in-differences analysis to estimate the impact of recreational markets on fatalities from motor vehicle accidents, suicide, and opioid overdose in seven states: Colorado, Washington, Oregon, Alaska, Nevada, California, and Massachusetts. States with comprehensive medical cannabis programs with similar pre-trends in deaths were used as comparisons. For each outcome, a pooled estimate was generated with a meta-analysis using random effects models. The results revealed substantial increases in crash fatalities in Colorado, Oregon, Alaska, and California of 16%, 22%, 20%, and 14%, respectively. Based on estimates from all seven states, recreational markets were associated with a 10% increase in motor vehicle accident deaths, on average. This study found no evidence that recreational markets impacted suicides. Most states saw a relative reduction in opioid overdose death that ranged between 3 and 28%. On average, recreational markets were associated with an 11% reduction in opioid overdose fatalities.

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.

Association of Racial Disparity of Cannabis Possession Arrests Among Adults and Youths With Statewide Cannabis Decriminalization and Legalization

Question

How are statewide cannabis policies (eg, legalization, decriminalization, no policy change) associated with cannabis arrest rate racial disparities among adults and youths?

Findings

In this case-control study of 43 US states with and without cannabis policy changes, decriminalization and legalization were associated with large reductions in race-based arrests among adults; however, the timing of effects suggests differential policy effects. Among youth, only decriminalization was associated with reductions in arrests and arrest disparities; cannabis arrests for adults and youth increased over time in states that did not implement a cannabis policy change.

Meaning

The study findings suggest that increases in arrest rate disparities in states without legalization or decriminalization highlight the need for targeted interventions to address racial injustice.

Importance

Despite calls for cannabis decriminalization and legalization, research investigating the association of policy with arrest rates and racial disparities is scarce.

Objectives

To examine racial differences in cannabis arrest rates among adults and youths after statewide decriminalization, legalization, and no policy changes.

Design, Setting, and Participants

This case-control study used race-based arrest data from the Uniform Crime Reporting Program and Surveillance, Epidemiology, and End Results county-level population data from January 2000 through December 2019. Data were analyzed in July 2021. Event-study analyses based on the arrest rates from 43 US states were conducted to compare preimplementation and postimplementation differences in arrest rates for states with decriminalization, legalization, and no policy changes.

Exposures

Nine states implemented legalization, 8 implemented decriminalization, and 26 had no policy change.

Main Outcomes and Measures

Outcome measures were cannabis arrest rates for Black and White adults and youths per year and by state, while controlling for several covariates.

Results

Rates were reported per 100 000. When comparing absolute differences in arrests from January to December 2008 (before policy changes) to January to December 2019, legalization was associated with 561 and 195 fewer arrests and decriminalization with 448.6 and 117.1 fewer arrests for Black and White adults, respectively. States without a policy change saw reductions of 47.5 and 33.0 arrests for Black and White adults, respectively. Among youth, legalization was associated with 131.1 and 131.2 fewer arrests and decriminalization with 156.1 and 124.7 fewer arrests for Black and White youths, respectively. Among states without a policy change, arrests reduced by 35 and 52.4 for Black and White youths, respectively. Plotted trends of the arrest ratios from January 2000 through December 2019 suggests racial disparities remained over time. Event-study analyses suggest that decriminalization was associated with an arrest rate reduction for Black and White adults and youths. The timing of reductions suggests differential policy effects. Arrest disparities increased in states that did not have a cannabis policy change.

Conclusions and Relevance

In this case-control study of states with and without cannabis decriminalization and legalization policies, increased arrest rate disparities in states without either policy highlight the need for targeted interventions to address racial injustice.

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

Importance

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

Objective

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

Design, Setting, and Participants

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

Exposures

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

Main Outcomes and Measures

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

Results

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

Conclusions and Relevance

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

Medical Marijuana Laws and Suicide

In the current study we use a synthetic control group design to estimate the causal effect of a medical marijuana initiative on suicide risk. In 1996, California legalized marijuana use for medical purposes. Implementation was abrupt and uniform, presenting a "natural experiment." Utilizing a panel dataset containing annual frequencies of Total, gun, and non-gun suicides aggregated by state for the years 1970-2004, we construct a control time series for California as a weighted combination of the 41 states that did not legalize marijuana during the analysis period. Post-intervention differences for California and its constructed control time series can be interpreted as the effects of the medical marijuana law on suicide. Significance of the effects were assessed with permutation tests. Our findings suggest that California's 1996 legalization resulted in statistically significant (p<.05) reductions in suicides and gun suicides, but only a non-significant reduction in non-gun suicides (p≥.488). Since the effect for non-gun suicides was indistinguishable from chance, we infer that the overall causal effect was realized through gun suicides. The mechanism could not be determined, however. Participation in the medical marijuana program legally disqualifies participants from purchasing guns. But since most suicides involve guns, it is possible that the effect on total suicide is driven by gun suicide alone.

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.

Changes in alcohol and cigarette consumption in response to medical and recreational cannabis legalization: Evidence from U.S. state tax receipt data

BACKGROUND

Whether medical or recreational cannabis legalization impacts alcohol or cigarette consumption is a key question as cannabis policy evolves, given the adverse health effects of these substances. Relatively little research has examined this question. The objective of this study was to examine whether medical or recreational cannabis legalization was associated with any change in state-level per capita alcohol or cigarette consumption.

METHODS

Dependent variables included per capita consumption of alcohol and cigarettes from all 50 U.S. states, estimated from state tax receipts and maintained by the Centers for Disease Control and National Institute for Alcohol Abuse and Alcoholism, respectively. Independent variables included indicators for medical and recreational legalization policies. Three different types of indicators were separately used to model medical cannabis policies. Indicators for the primary model were based on the presence of active medical cannabis dispensaries. Secondary models used indicators based on either the presence of a more liberal medical cannabis policy ("non-medicalized") or the presence of any medical cannabis policy. Difference-in-difference regression models were applied to estimate associations for each type of policy.

RESULTS

Primary models found no statistically significant associations between medical or recreational cannabis legalization policies and either alcohol or cigarette sales per capita. In a secondary model, both medical and recreational policies were associated with significantly decreased per capita cigarette sales compared to states with no medical cannabis policy. However, post hoc analyses demonstrated that these reductions were apparent at least two years prior to policy adoption, indicating that they likely result from other time-varying characteristics of legalization states, rather than cannabis policy.

CONCLUSION

We found no evidence of a causal association between medical or recreational cannabis legalization and changes in either alcohol or cigarette sales per capita.

Youth and Adult Arrests for Cannabis Possession After Decriminalization and Legalization of Cannabis

IMPORTANCE

Civil liberty advocates typically support legalization of cannabis, which targets adult use, rather than decriminalization, which can affect both adults and youths. However, it is unknown how arrests of youths for cannabis possession change when adult use of cannabis is legalized.

OBJECTIVE

To model changes in arrest rates of adults and youths after decriminalization and legalization of cannabis.

DESIGN, SETTING, AND PARTICIPANTS

This quasi-experimental study used the publicly available Uniform Crime Reporting Program Data: Arrests by Age, Sex, and Race administrative data set to examine arrest rates in 38 states from January 1, 2000, to December 31, 2016. Adult (age, ≥18 years) and youth (age, <18 years) arrests for possession of cannabis were examined. States were excluded if they did not report complete arrest data or if a policy was implemented that reduced penalties for possession of cannabis but fell short of decriminalization. Fixed-effects regression was used in an extended difference-in-differences framework. The analyses in their final form were conducted between January 17 and February 28, 2019.

EXPOSURE

Living in a state with a cannabis decriminalization policy (ie, making the penalty for cannabis possession similar to the small fine for a traffic violation) or legalization policy (ie, creating a legal supply of cannabis along with the removal of penalties for possession of a small amount of cannabis for recreational use).

MAIN OUTCOME AND MEASURES

State cannabis possession arrest rate per 100 000 population.

RESULTS

Data from 38 states were examined, including 4 states with cannabis legalization policies and 7 states with cannabis decriminalization policies. The adult arrest rate decreased by 131.28 (95% CI, 106.23-154.21) per 100 000 population after the implementation of decriminalization and 168.50 (95% CI, 158.64-229.65) per 100 000 population after the implementation of legalization. The arrest rate for youths decreased by 60 (95% CI, 42-75) per 100 000 population after decriminalization but did not significantly change after legalization in a state (7 per 100 000 population; 95% CI, -15 to 30).

CONCLUSIONS AND RELEVANCE

Legalization, as implemented through 2016, did not appear to reduce arrests for cannabis possession among youths, despite having benefited adults. The study's findings suggest that decriminalization reduces youth arrests in most cases, but these findings also suggest that any benefit for youths could be lost when adult use has also been legalized. To address this problem, it appears that state decriminalization policies should take the additional step to explicitly describe when youths can be arrested for possession of small amounts of cannabis.

The impact of adolescent exposure to medical marijuana laws on high school completion, college enrollment and college degree completion

BACKGROUND

There is concern that medical marijuana laws (MMLs) could negatively affect adolescents. To better understand these policies, we assess how adolescent exposure to MMLs is related to educational attainment.

METHODS

Data from the 2000 Census and 2001-2014 American Community Surveys were restricted to individuals who were of high school age (14-18) between 1990 and 2012 (n=5,483,715). MML exposure was coded as: (i) a dichotomous "any MML" indicator, and (ii) number of years of high school age exposure. We used logistic regression to model whether MMLs affected: (a) completing high school by age 19; (b) beginning college, irrespective of completion; and (c) obtaining any degree after beginning college. A similar dataset based on the Youth Risk Behavior Survey (YRBS) was also constructed for confirmatory analyses assessing marijuana use.

RESULTS

MMLs were associated with a 0.40 percentage point increase in the probability of not earning a high school diploma or GED after completing the 12th grade (from 3.99% to 4.39%). High school MML exposure was also associated with a 1.84 and 0.85 percentage point increase in the probability of college non-enrollment and degree non-completion, respectively (from 31.12% to 32.96% and 45.30% to 46.15%, respectively). Years of MML exposure exhibited a consistent dose response relationship for all outcomes. MMLs were also associated with 0.85 percentage point increase in daily marijuana use among 12th graders (up from 1.26%).

CONCLUSIONS

Medical marijuana law exposure between age 14 to 18 likely has a delayed effect on use and education that persists over time.

Evaluating the public health impacts of legalizing recreational cannabis use in the United States

BACKGROUND AND AIMS

Since 2012 four US states have legalized the retail sale of cannabis for recreational use by adults, and more are likely to follow. This report aimed to (1) briefly describe the regulatory regimes so far implemented; (2) outline their plausible effects on cannabis use and cannabis-related harm; and (3) suggest what research is needed to evaluate the public health impact of these policy changes.

METHOD

We reviewed the drug policy literature to identify: (1) plausible effects of legalizing adult recreational use on cannabis price and availability; (2) factors that may increase or limit these effects; (3) pointers from studies of the effects of legalizing medical cannabis use; and (4) indicators of cannabis use and cannabis-related harm that can be monitored to assess the effects of these policy changes.

RESULTS

Legalization of recreational use will probably increase use in the long term, but the magnitude and timing of any increase is uncertain. It will be critical to monitor: cannabis use in household and high school surveys; cannabis sales; the number of cannabis plants legally produced; and the tetrahydrocannabinol (THC) content of cannabis. Indicators of cannabis-related harms that should be monitored include: car crash fatalities and injuries; emergency department presentations; presentations to addiction treatment services; and the prevalence of regular cannabis use among young people in mental health services and the criminal justice system.

CONCLUSIONS

Plausible effects of legalizing recreational cannabis use in the United States include substantially reducing the price of cannabis and increasing heavy use and some types of cannabis-related harm among existing users. In the longer term it may also increase the number of new users.

The Impact of the Minimum Legal Drinking Age on Alcohol-Related Chronic Disease Mortality

BACKGROUND

The minimum legal drinking age (MLDA) of 21 has been associated with a number of benefits compared to lower MLDAs, including long-term effects, such as reduced risk for alcoholism in adulthood. However, no studies have examined whether MLDA during young adulthood is associated with mortality later in life. We examined whether individuals exposed to permissive MLDA (<21) had higher risk of death from alcohol-related chronic disease compared to those exposed to the 21 MLDA. Because prior work suggests that MLDA affects college students differently, we also conducted conditional analyses based on ever having attended college.

METHODS

Data from the 1990 through 2010 U.S. Multiple Cause-of-Death files were combined with data on the living population and analyzed. We included individuals who turned 18 during the years 1967 to 1990, the period during which MLDA varied across states. We examined records on death from several alcohol-related chronic diseases, employing a quasi-experimental approach to control for unobserved state characteristics and stable time trends.

RESULTS

Individuals who reported any college attendance did not exhibit significant associations between MLDA and mortality for the causes of death we examined. However, permissive MLDA for those who never attended college was associated with 6% higher odds for death from alcoholic liver disease, 8% higher odds for other liver disease, and 7% higher odds for lip/oral/pharynx cancers (odds ratio [OR] = 1.06, 95% confidence interval [CI] [1.02, 1.10]; OR = 1.08, 95% CI [1.03, 1.13]; OR = 1.07, 95% CI [1.03, 1.12], respectively).

CONCLUSIONS

The 21 MLDA likely protects against risk of death from alcohol-related chronic disease across the lifespan, at least for those who did not attend college. This is consistent with other work that shows that the long-term association between MLDA and alcohol-related outcomes is specific to those who did not attend college.