Research paper
Do medical cannabis laws encourage cannabis use?

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Abstract

Medical cannabis is a contentious issue in the United States, with many fearing that introduction of state laws will increase use among the general population. The present study examined whether the introduction of such laws affects the level of cannabis use among arrestees and emergency department patients. Using the Arrestee Drug Abuse Monitoring system, data from adult arrestees for the period 1995–2002 were examined in three cities in California (Los Angeles, San Diego, San Jose), one city in Colorado (Denver), and one city in Oregon (Portland). Data were also analysed for juvenile arrestees in two of the California cities and Portland. Data on emergency department patients from the Drug Abuse Warning Network for the period 1994–2002 were examined in three metropolitan areas in California (Los Angeles, San Diego, San Francisco), one in Colorado (Denver), and one in Washington State (Seattle). The analysis followed an interrupted time-series design. No statistically significant pre-law versus post-law differences were found in any of the ADAM or DAWN sites. Thus, consistent with other studies of the liberalization of cannabis laws, medical cannabis laws do not appear to increase use of the drug. One reason for this might be that relatively few individuals are registered medical cannabis patients or caregivers. In addition, use of the drug by those already sick might “de-glamorise” it and thereby do little to encourage use among others.

Introduction

There are currently 12 states in the USA with laws that remove penalties for the cultivation, possession and use of cannabis for medical reasons (Alaska, California, Colorado, Hawaii, Maine, Maryland, Montana, Nevada, Oregon, Rhode Island, Vermont and Washington) (Drug Policy Alliance, 2006, NORML, 2006). In most cases the law allows a written or oral recommendation by a physician stating that the patient will benefit from use of cannabis to serve as a medical necessity defense should the patient be arrested on charges of cannabis possession. These so-called “effective” laws differ from medical cannabis research laws and “symbolic” laws, such as Arizona's Proposition 200, which do not accord the same legal protection to patients who use cannabis (Pacula, Chriqui, Reichmann & Terry-McElrath, 2002; Schmitz & Thomas, 2004).

Medical use of cannabis has become an increasingly contentious issue as it is the primary arena in which the forces on either side of the prohibition-legalization debate engage one another, with both sides seeing the introduction of state laws as an initial step on the road to decriminalization of the drug (Clark, 2000, Schrag, 2002, Stein, 2002). The federal government vehemently opposes state-level introduction of medical cannabis laws on a number of grounds, including a fear that they have the potential to increase use among the general population (especially young people) through sending the message that cannabis use is acceptable (Clark, 2000, Medical Marijuana ProCon, 2006, Schrag, 2002). Moreover, this “wrong message” argument is not confined to the federal government. The authors of the 1999 Institute of Medicine Report observed that “almost everyone” that spoke to its study team “about the potential harms posed by medical marijuana felt that it would send the wrong message to children and teenagers”. The Report goes on to state that: “The question here is not whether marijuana can be both harmful and helpful but whether the perception of its benefits will increase its abuse. For now any answer to the question remains conjecture. Because marijuana is not an approved medicine, there is little information about the consequences of its medical use in modern society” (Institute of Medicine, 1999, p. 101).

If the “wrong message” hypothesis is correct, one would anticipate greater use of cannabis and attendant problems to follow the passage of a state's medical cannabis law. We address this issue by examining trends in cannabis use among two high risk subgroups (arrestees and emergency department patients) from the mid-1990s through 2002 in five cities and five metropolitan areas in states that had passed medical cannabis laws in the previous 10 years.

Section snippets

Study design and data analyses

Data on cannabis use among arrestees were extracted from the Arrestee Drug Abuse Monitoring (ADAM) system which was established (as the Drug Use Forecasting program) by the National Institute of Justice in 1987 and ran until 2003 (National Institute of Justice, 1990, National Institute of Justice, 2004). Twenty-three of the 38 ADAM sites active at the time that the program was discontinued had been in the program long enough to provide a sufficient number of data points to use in time-series

ADAM data

The average number of adult arrestees per quarter who provided urine samples was 328 in Denver (range 180–696), 285 in Portland (range 0–754), and 885 in the three California cities combined (range 382–2152). The wide range across quarters in California was due to the fact that Los Angeles contributed very little or no data to the quarterly counts for the period 2000 through 2002. While this would not affect the results for the immediate post-law period in California (1997–1999), it could

Discussion

Our results indicate that the introduction of medical cannabis laws was not associated with an increase in cannabis use among either arrestees or emergency department patients in cities and metropolitan areas located in four states in the USA (California, Colorado, Oregon and Washington). For the arrestee data, the results are most persuasive for California and Oregon since the post-law time-series in these states were fairly long. This is also true of the DAWN analysis of the California and

Acknowledgements

This work was supported by grant # 048568 from the Robert Wood Johnson Foundation Substance Abuse Policy Research Program.

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