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.

     

Developing Public Health Regulations for Marijuana: Lessons From Alcohol and Tobacco

Until November 2012, no modern jurisdiction had removed the prohibition on the commercial production, distribution, and sale of marijuana for nonmedical purposes—not even the Netherlands. Government agencies in Colorado and Washington are now charged with granting production and processing licenses and developing regulations for legal marijuana, and other states and countries may follow. Our goal is not to address whether marijuana legalization is a good or bad idea but, rather, to help policymakers understand the decisions they face and some lessons learned from research on public health approaches to regulating alcohol and tobacco over the past century.Marijuana legalization is no longer an abstract notion. In November 2012, voters in Colorado and Washington passed initiatives that not only made it legal to possess up to an ounce of marijuana for nonmedical purposes but also allow for-profit firms to supply the market. Colorado’s initiative additionally allows home production. Although marijuana remains illegal under federal law, policymakers in these states are now developing regulatory regimes that will allow licensees to produce and sell marijuana and other cannabis products, including infused candies and other edibles, to anyone who is aged 21 years or older. (“Marijuana” is an American term, customarily applied to the dried leaves and flowers of the cannabis plant. There are other cannabis plant products, including resin, which is referred to in the United States as “hashish.” The majority of cannabis consumed in the United States is in the form of marijuana, which is probably why initial state legalization statutes that have passed are specifically about “marijuana” although even these laws do not mean to be restrictive in their terms. For example, Washington speaks of “marijuana-infused” drinks and edibles, and Colorado’s Amendment 64 defines “marijuana” to be all possible products of the plant except industrial hemp.) Bills to legalize marijuana are being introduced in other states, and we will likely see more ballot initiatives in future elections.Although many jurisdictions have experimented with alternatives to strict marijuana prohibition, including decriminalization, medical marijuana, and the Dutch “coffee shops,” no industrialized nation has legalized the cultivation, processing, distribution, and supply of marijuana for recreational purposes in the modern era—not even the Netherlands. In the Netherlands, de facto legalization extends only to retail sales of up to 5 grams; wholesale distribution of marijuana to coffee shops remains illegal and is actively enforced. That is not to say that it has never been legal; in fact, marijuana was a legal commodity in the United States until the early 1900s. But regulatory policy on the cultivation, processing, distribution, and sale of marijuana and its derivative products is unprecedented in the modern era.Because there are no modern examples of marijuana regulation, policymakers are confronting many new questions about how to manage a marijuana market. Should the number of licensees be restricted, and, if so, how should those scarce licenses be allocated? Should vertical integration be allowed, or should there be separate licenses for growing, processing, and selling marijuana? What product safety requirements should be considered (in terms of specific ingredients allowed or disallowed), and who will be responsible for testing the product? How restrictive should licenses be in terms of permitted quantity and potency? Should taxes be assessed per unit weight, as a percentage of value (ad valorem), or on some other basis, such as Δ-9-tetrahydrocannabinol (THC) content? Should marijuana be sold in conventional stores alongside other products or only in specialized venues? What about within-state Internet sales? Although the questions are new for marijuana, policymakers have grappled with similar questions pertaining to alcohol and tobacco, raising the question of what lessons can be learned from these 2 substances and applied to marijuana policy.We have summarized insights and ideas that grew out of a meeting of alcohol, tobacco, and illicit drug policy experts hosted by the RAND Drug Policy Research Center on February 11, 2013, to foster discussions about how one might regulate marijuana to promote public health objectives assuming a decision to legalize has already been made. The arguments here do not necessarily reflect the opinions of every coauthor but, instead, reflect a general consensus of ideas that grew out of those discussions. The conference was filmed by C-SPAN.1     

State medical marijuana laws: understanding the laws and their limitations

Significant attention has been given to the debate regarding allowances for medical marijuana use since the 1996 California and Arizona ballot initiatives. State medical marijuana allowances, however, have existed since the mid-1970s. Much of the current debate stems from confusion about the various ways states approach the issue. In this paper, we present original legal research on current state medical marijuana laws identifying four different ways states statutorily enable the medical use of marijuana. We discuss the tension these approaches have with federal law as well as their implications regarding real access for patients. In addition, we present information on how a small number of states are trying to deal with the issue of access within the context of their medical marijuana laws, and discuss the implication of various supply approaches on the enforcement of other state marijuana laws.     

Author Index to Volume 28, 2000–2001

Authors Index

Author Index to Volume 28, 2000–2001     

State mental health parity laws: cause or consequence of differences in use?

A new wave of state and federal legislation affecting mental health insurance was passed during the 1990s. Although patient advocacy groups have hailed the passage of numerous parity laws, it is unclear whether this activity represents a major improvement in insurance benefits or significantly increases access to mental health care. We investigated this issue with data from two new national studies sponsored by the Robert Wood Johnson Foundation. We found that states with below-average utilization were more likely to enact state legislation, but utilization in those states continues to lag behind the rest of the nation.     

College Students' Use of Cocaine

After experiencing a period of rapid decline between 1986 and 1994, cocaine use is once again on the rise in the United States. The increased prevalence of use among college students is particularly troubling because of its potential impact on human capital acquisition and long-term labor market success. Merging information on the price of cocaine and marijuana from the U.S. Drug Enforcement Agency with data on cocaine use from the College Alcohol Study, we investigate the demand for cocaine in the college population. We find evidence that participation in cocaine use by college students is responsive to changes in the price of cocaine and marijuana and that cocaine and marijuana are economic complements for this population. Further investigation revealed significant differences in the demand for cocaine by those less than age 21 and those at least age 21, years, with the younger age group being more responsive to changes in the price of cocaine. No difference is found, however, in the demand for cocaine across gender.     

Letter: Economic modelling of the gateway effect

Although a significant number of empirical studies provide evidence of sequencing in drug use, economic theory remains focused on addiction to a single substance. This paper presents a general model of substance use that allows for the possibility of multi-commodity habit formation and can be used to analyse the intertemporal relationship between the consumption of legal and illicit drugs, or the gateway effect. A simple two-drug model is analysed and conditions for the existence of multi-commodity habit formation are examined. It is found in the case of multi-commodity habit formation that the marginal utility of initiating a new drug is higher when there is prior consumption of the other drug. Further, it is found that the individual will initiate drug consumption with that drug that has the lowest marginal cost. The particular sequencing of drug use that is observed in empirical data is explained by differences in the marginal cost of consuming legal and illegal drugs. © 1997 John Wiley & Sons, Ltd.     

College students' use of cocaine

After experiencing a period of rapid decline between 1986 and 1994, cocaine use is once again on the rise in the United States. The increased prevalence of use among college students is particularly troubling because of its potential impact on human capital acquisition and long-term labor market success. Merging information on the price of cocaine and marijuana from the U.S. Drug Enforcement Agency with data on cocaine use from the College Alcohol Study, we investigate the demand for cocaine in the college population. We find evidence that participation in cocaine use by college students is responsive to changes in the price of cocaine and marijuana and that cocaine and marijuana are economic complements for this population. Further investigation revealed significant differences in the demand for cocaine by those less than age 21 and those at least age 21, years, with the younger age group being more responsive to changes in the price of cocaine. No difference is found, however, in the demand for cocaine across gender.     

Alcohol and marijuana use among college students: economic complements or substitutes?

Previous research has shown that the recent tightening of college alcohol policies has been effective at reducing college students' drinking. Over the period in which these stricter alcohol policies have been put in place, marijuana use among college students has increased. This raises the question of whether current policies aimed at reducing alcohol consumption are inadvertently encouraging marijuana use. This paper begins to address this question by investigating the relationship between the demands for alcohol and marijuana for college students using data from the 1993, 1997 and 1999 waves of the Harvard School of Public Health's College Alcohol Study (CAS). We find that alcohol and marijuana are economic complements and that policies that increase the full price of alcohol decrease participation in marijuana use.