Opponents of marijuana decriminalization and/or legalization frequently assert a correlation between pot use and increased criminal activity, alleging that even medical marijuana legalization poses a threat to public health and safety. However, science is not on their side. According to a major new study by University of Texas at Dallas researchers has determined that there is no association between legalization of medical cannabis and higher incidence of crime, and moreover, it actually may be related to reductions in certain types of crime.
The study results are published in the journal PLOS ONE, titled: “The Effect of Medical Marijuana Laws on Crime: Evidence from State Panel Data, 1990-2006” (March 26, 2014DOI: 10.1371/journal.pone.0092816), co-authored by Robert G. Morris, Michael TenEyck, J. C. Barnes, and Tomislav V. Kovandzic — all associated with UT Dallas’s Program in Criminology.
The UT Dallas research team began its work in summer 2012, after repeatedly hearing claims that medical marijuana legalization (MML) posed a danger to public health in terms of exposure to violent crime and property crime. The study coauthors note that legalization of medical cannabis by 20 states and the District of Columbia, and legalization of recreational use as well in Colorado and Washington, has re-ignited political and public interest in the impact of marijuana legalization on a range of outcomes, and that despite a long history of marijuana use for medical purposes, policymakers and in some instances even the scientific community, have been quick to suggest potential problematic social outcomes of marijuana legalization. Likewise in Canada, where medical marijuana use has been legal for patients vetted by medical pain specialists since 2001, the Conservative government is using the crime-association argument as a pretext to prohibit medical users growing their own, and restricting legal access to the drug to federally licensed commercial grow-ops, and to impose harsh mandatory minimum criminal sentences for anyone convicted of possession of more then six marijuana plants. Meanwhile, the opposition Liberal Party and its leader Justin Trudeau, currently leading in polls, have strongly endorsed decriminalization and eventually regulated legalization of recreational marijuana.
The UT Dallas researchers observe that medical marijuana legalization (MML) opponents cite many mechanisms by which MML might affect crime rates, one being a greater number of marijuana users, which they suggest may lead to a broader social acceptance of drug using behaviors and drug users and serve as a “gateway” to harder drugs like cocaine and heroin, and that MML could also lead to long-term increases in crime as an ever-growing number of illicit drug users engage in serious predatory crimes to support their habits. And, naysayers contend, even if MML does not lead to a rise in marijuana use (especially among youth), it could still stimulate crime as newly opened medical marijuana dispensaries provide criminals with a highly attractive target with their stocks of high quality marijuana and customers carrying large amounts of cash.
Some in the law enforcement community in both the U.S. and Canada assert that an increasing number of home invasion robberies and associated violence resulting in the victimization of those cultivating and possessing marijuana will result from MML. However, the study coauthors observe that empirical research on the direct relationship between medical marijuana laws and crime is scant and the consequences of marijuana use on crime remain unknown, and that although anecdotal evidence abounds to support the negative theses, and a few single-jurisdiction and cross-sectional studies have examined the MML-crime link, no single analysis has assessed the overall consequences of medical marijuana laws on crime rates across the United States. Consequently, their study seeks to inform the debate by providing a comprehensive evaluation of the effects of state MML on state crime rates.
The coauthors say their findings run counter to arguments suggesting the legalization of marijuana for medical purposes poses a danger to public health in terms of exposure to violent crime and property crimes, and that their results did not support a crime-exacerbating effect of MML. Alternatively, they determined that state MML may be correlated with a reduction in homicide and assault rates, net of other covariates.
The central finding gleaned from the UT Dallas study was that MML is not predictive of higher crime rates and may be related to reductions in rates of homicide and assault, while robbery and burglary rates were unaffected by medicinal marijuana legislation which directly contradicts the assertion that medical marijuana dispensaries and grow houses ipso facto lead to an increase in victimization due to potentially greater crime opportunity associated with the amount of drugs and cash that are present. The researchers note that their findings are concurrent with prior research suggesting that medical marijuana dispensaries may actually reduce crime in the immediate vicinity.
“We’re cautious about saying, ‘Medical marijuana laws definitely reduce homicide.’ That’s not what we’re saying,” comments Dr. Robert Morris lead author of the study published in the journal PLOS ONE, in a UT Dallas release. “The main finding is that we found no increase in crime rates resulting from medical marijuana legalization. In fact, we found some evidence of decreasing rates of some types of violent crime, namely homicide and assault.”
The study tracked crime rates across all 50 states between 1990 and 2006, when 11 states legalized marijuana for medical use: Alaska, California, Colorado, Hawaii, Maine, Montana, Nevada, Oregon, Rhode Island, Vermont and Washington. Since the time period the study covered, 20 states and Washington, D.C., have also legalized marijuana for medical use.
Using crime data from the FBI’s Uniform Crime Report, the researchers studied rates for homicide, rape, robbery, assault, burglary, larceny and auto theft, teasing out an effect for the passing of medical marijuana laws.
“This new information, along with continued education of the public on the realities of the negative aspects of smoking marijuana — which there are considerable negative attributes — will make the dialogue between those opposed and in favor of legalization on more of an even playing field,” Dr. Morris contends. It takes away the subjective comments about the link between marijuana laws and crime so the dialogue can be more in tune with reality.”
Robbery and burglary rates were unaffected by medical marijuana legalization, according to the study — findings that run counter to the claim that marijuana dispensaries and grow houses lead to an increase in victimization because of the opportunities for crime linked to the amount of drugs and cash that are present.
Dr. Morris notes that the models accounted for an exhaustive list of sociodemographic and econometric variables that are well-established links to changes in crime rates, including statistics on poverty, unemployment, college education, prison inmates and even the amount of beer consumed per person per year. Data came from the U.S. Census Bureau, the Bureau of Economic Analysis and the Bureau of Labor Statistics.
“The results are remarkable,” Dr. Morris observes. “It’s pretty telling. It will be interesting to see what future studies hold.”
In summary, the UT Dallas research team’s findings contradict contentions that legalization of marijuana for medical purposes poses a social side-effect danger to public health in the form of greater exposure to violent crime and property crimes, and that in point of fact medical marijuana laws were not found to have a crime exacerbating effect on any of seven particular crime types focused on. On the contrary, their findings indicated that MML precedes a reduction in homicide and assault, and while it is important to remain cautious when interpreting these findings as evidence that MML reduces crime, they do fall in line with recent evidence and conform to the longstanding counter-assertion that marijuana legalization may lead to a reduction in alcohol use due to individuals substituting marijuana for alcohol, and that given the extensively-documented relationship between alcohol and both violent and non-violent crime (not to mention manifold other social pathologies), it may turn out that substituting marijuana for alcohol leads to minor reductions in violent crimes that can be detected at the state level, although the researchers stress that more research is needed.
Dr. Robert Morris is Associate Professor of Criminology in the School of Economic, Political & Policy Sciences (EPPS) at UT Dallas, holds a Ph.D. in Criminal Justice from Sam Houston State University, and is also Director of the Center for Crime and Justice Studies within EPPS.
Dr. Morris’ research agenda focuses upon contemporary issues in crime and justice, including both the etiology of contemporary criminal offending (e.g., technology driven crimes such as computer hacking) as well as contemporary issues in the application of criminal justice. He has published work in peer-reviewed research journals including Justice Quarterly, Intelligence, Journal of Quantitative Criminology, Crime and Delinquency, the Journal of Criminal Justice and many others on topics including life-course criminology, corrections administration, technology driven crimes, recidivism, prison inmate behavior, policy analysis, among other areas. He also specializes in advanced quantitative statistical methods. Dr. Morris is also the recipient of numerous research and teaching awards, and in August, 2011 was awarded the prestigious University of Texas System Regents’ Outstanding Teaching Award. In 2012, he was awarded the William Simon/SAGE publications Outstanding Paper Award from the Academy of Criminal Justice Sciences (with Dr. Erin Orrick) for a manuscript entitled Do Parole Violators Pose a Public Safety Threat? An Analysis of Prison Misconduct.
Study coauthor http://www.utdallas.edu/~tvk071000/Dr. Tomislav V. Kovandzic is a faculty member in the School of Economic, Political and Policy Sciences at UT-Dallas. Dr. Kovandzic teaches courses on research methods, statistics, gun control, extent and measurement of crime, and crime patterns, and his primary areas of research interest are gun control, crime policy, and deterrence/incapacitation.
Coauthor J.C. Barnes, Ph.D. is a UT Dallas Assistant Professor whose research aims to uncover the biosocial correlates of antisocial behavior. Dr. Barnes’s publications have appeared in a range of outlets such asÂ Developmental Psychology, Behavior Genetics, Journal of Theoretical Biology, Criminology, Justice Quarterly, Crime & Delinquency, Journal of Interpersonal Violence, Death Studies, Criminal Justice and Behavior, Aggressive Behavior, Journal of Criminal Justice, Intelligence, Journal of Marriage and Family, Youth Violence and Juvenile Justice, American Journal of Health Behavior, Biodemography and Social Biology, Physiology & Behavior, and Comprehensive Psychiatry, among others. The Barnes Lab aims to uncover how biological and genetic factors interact with environmental exposures to affect antisocial behavior.
UT Dallas doctoral student Michael TenEyck of the UT Dallas criminology program, also contributed to the study as co-author. Once data are available, the researchers plan to investigate the relationship between recreational marijuana legalization and crime in Washington and Colorado, where the legalized marijuana marketplace is taking shape.
While it’s too soon to say if there are definitive drawbacks to legalizing marijuana for medical purposes, Dr. Morris observes, the study shows that legalization does not pose a serious crime problem, at least at the state level, and that: “This new information, along with continued education of the public on the realities of the negative aspects of smoking marijuana — which there are considerable negative attributes — will make the dialogue between those opposed and in favor of legalization on more of an even playing field,” Morris said. “It takes away the subjective comments about the link between marijuana laws and crime so the dialogue can be more in tune with reality.”
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The University of Texas at Dallas