Archive for the ‘SCIENCE’ category

Study: Habitual Marijuana Smoking Not Associated With Increased Risk Of Lung Cancer

June 23rd, 2014

Subjects who regularly inhale cannabis smoke possess no greater risk of contracting lung cancer than do those who consume it occasionally or not at all, according to data published online ahead of print in the International Journal of Cancer.

An international team of investigators from Canada, New Zealand, the United Kingdom, and the United States analyzed data from six case-control studies involving over 5,000 subjects (2,159 cases and 2,985 controls) from around the world.

Authors concluded, “Results from our pooled analyses provide little evidence for an increased risk of lung cancer among habitual or long-term cannabis smokers.”

Investigators had previously presented their data at the 2013 annual meeting of the American Academy for Cancer Research.

Their findings are similar to those of a 2013 review published in the journal Annals of the American Thoracic Society, which concluded: “[H]abitual use of marijuana alone does not appear to lead to significant abnormalities in lung function. … Overall, the risks of pulmonary complications of regular use of marijuana appear to be relatively small and far lower than those of tobacco smoking.”

An accompanying commentary in the same journal affirmed, “[C]annabis smoking does not seem to increase risk of chronic obstructive pulmonary disease (COPD) or airway cancers. In fact, there is even a suggestion that at low doses cannabis may be protective for both conditions.”

Preclinical studies have documented that cannabinoids possess potent anti-cancer properties, including the inhibition of lung cancer cell growth. To date, however, scientists have yet to conduct controlled clinical trials replicating these results in human subjects.

The abstract of the study, “Cannabis smoking and lung cancer risk: Pooled analysis in the International Lung Cancer Consortium,” appears online here.

The Fear of Pleasure: Why CBD-Only Legislation is Not a Real Solution

June 17th, 2014

Most of us were caught off-guard by the rush of states this year that approved the limited use of CBD-only marijuana extracts because these traditionally conservative states had heretofore rejected the medical use of marijuana. So it seems worth a moment to consider how this occurred, and what it means on a grander scale.

But first, a little recent history.

Throughout this year’s state legislative season, a total of 10 states enacted laws seeking to provide limited access to medical marijuana products that contain high levels of CBD and virtually no THC for qualified, typically pediatric patients suffering from severe and disabling seizures: Alabama, Florida, Iowa, Kentucky, Mississippi, Missouri, South Carolina, Tennessee, Utah and Wisconsin.

On one level, this unexpected embrace of the medicinal qualities of marijuana by states that previously rejected the concept must be seen as a favorable development. These serendipitous adoptions reflect a degree of compassion not obvious in the previous legislative debates in those states.

But it is far from certain that these laws will actually help the young patients they are intended to help.

First, such products are primarily only available in a handful of states like California and Colorado and none of these new state laws create a viable in-state supply source for such products. Further, even if a patient from out-of-state could find these products in California or Colorado, it would be a violation of federal law (and also likely state law) to take the medicine back to their home state.

And while some of these laws attempt to establish CBD research projects at their major universities or research hospitals, recent experience demonstrates that few universities or research hospitals are willing to enter this confusing field while marijuana remains a federal crime, and those that may be willing to take the bait will face a steep and long learning curve before the first patient will have high-CBD extracts available.

This legislative rush to CBD-only extracts also suggests (1) the degree to which elected officials are influenced by popular media, (2) their willingness to pick and choose the science they like (while ignoring the science they do not), and (3) the strong puritanical impulse that remains a factor with many elected officials.

And it all relates to the “Gupta Effect”. When CNN’s Dr. Sanjay Gupta’s report highlighting how high-CBD marijuana products control debilitating seizures among children suffering from Dravet’s syndrome (the most severe form of childhood epilepsy) went public, few Americans had even heard of cannabidiol. Most people were familiar with THC (tetrahydrocannabinol), the primary psychoactive ingredient in marijuana that principally accounts for the “high” that marijuana smokers enjoy, but had zero idea that CBD even existed.

Dr. Gupta, who had previously uncritically accepted the federal government’s consistent claim that marijuana had no legitimate medical use, when confronted with actual children whose lives had been transformed following their use of high-CBD marijuana extracts, understandably felt misled by the government’s anti-marijuana propaganda, and went public with two special programs introducing the importance of high-CBD extracts in reducing or eliminating seizures in these children.

In the second program Dr. Gupta made it clear that while CBD appeared to be the primary therapeutic ingredient for this class of patients, he also made the point that some level of THC was also required, because of what he termed the “entourage effect.” Without the THC, the CBD would either be less effective, or in some instances ineffective.

It’s embarrassing that so many of our elected officials would get their scientific understanding of the medical properties of marijuana from a popular television doctor, instead of conducting their own research into the available science, before moving legislation forward. But better they be motivated by a celebrity doctor than continue to ignore the benefits of medical marijuana altogether.

Of which there are a myriad.

The marijuana plant is one of the most studied biologically active substances of modern times. A search on PubMed, the repository for all peer-reviewed scientific papers, using the term “marijuana” yields nearly 20,000 scientific papers referencing the plant and/or its constituents, nearly half of which have been published just within the past decade. In addition, more than 100 controlled trials, involving thousands of subjects, have evaluated the safety and efficacy of cannabis and/or individual cannabinoids.

Most recently, a review of FDA-approved marijuana plant trials conducted by various California universities concluded, “Based on evidence currently available the Schedule I classification (for cannabis) is not tenable; it is not accurate that cannabis has no medical value, or that information on safety is lacking.” The best summary of this research can be found in the publication Emerging Clinical Applications for Cannabis and Cannabinoids, available on the NORML website. So the basic research is available for all who care to learn.

But few elected officials appear to be aware of this considerable body of science. Rather, the common refrain is to claim they cannot support the medical use of marijuana because the only evidence is “anecdotal”. These officials prefer to remain ignorant because it reinforces their preconceived notion that medical marijuana is a hoax perpetuated by those who simply wish to get “high”.

So what this latest rush to approve CBD-only marijuana products demonstrates, more than anything else, is the degree to which our public policy can frequently be influenced by a strong strain of puritanism that remains alive among our elected officials. If it feels good, it must be bad!

These many state legislators were willing to show some compassion by allowing the medical use of marijuana by these poor children suffering from multiple, disabling seizures, so long as the marijuana did not make them feel “high” (i.e., feel better!). These legislators are against pleasure, and if the use medical marijuana includes the feeling of pleasure, then it cannot be approved.

Excuse me, but is that not the purpose of using medicine when one is ill – to feel better?

Admittedly, for some of these puritans, the association of the word “high” with the use of marijuana may lie at the heart of the problem for them. Marijuana has long been demonized by conservatives, law enforcement, and many in the medical community, and that has spilled-over to the marijuana “high”.

If they understood that the marijuana “high” makes the user feel better, and that seriously ill patients almost always want (and need) to feel better, perhaps they could overcome their fear of medical marijuana. But for now at least, it is clear that in their view the marijuana “high”, like marijuana itself, is something to be avoided by responsible Americans, even if that precludes the use of medical marijuana by seriously ill patients.

It is time we moved beyond the notion that pleasure is bad, and stopped treating the marijuana “high” as something to be avoided, when it makes patient feel better. For them, feeling better and feeling high is often the same.

Federal Government To Increase Its Supply Of Marijuana For Clinical Research

May 6th, 2014

Federal agencies are moving forward with plans to increase the US government’s production of research-grade cannabis.

Last week, the US Drug Enforcement Administration (DEA) publicly announced in the Federal Register that it is increasing its marijuana production quota from 21 kilograms to 650 kilograms (about 1,443 pounds) in order to meet increasing demand for the plant from clinical investigators.

Federal regulations permit a farm at the University of Mississippi to cultivate set quantities of cannabis for use in federally approved clinical trials. Regulators at the DEA, the US Food and Drug Administration, PHS (Public Health Service), and the US National Institute on Drug Abuse must approve any clinical protocol seeking to study the plant’s effects in human subjects.

On various occasions, marijuana reform advocates and researchers have publicly criticized NIDA for failing to approve proposed trials seeking to assess the therapeutic benefits of cannabis. However, in March, federal regulators finally signed off on a long-delayed clinical protocol from researchers at the University of Arizona College of Medicine to evaluate the use of cannabis its in war veterans suffering from post-traumatic stress. Also this spring, lawmakers in several states, including Alabama, Kentucky, and Wisconsin, passed legislation encouraging state-sponsored clinical trials to assess the therapeutic potential of cannabidiol – a nonpsychotropic organic component of cannabis – in the treatment of intractable epilepsy.

“The additional supply [of cannabis] to be manufactured in 2014 is designed to meet the current and anticipated research efforts involving marijuana,” A NIDA spokesperson told TheHill.com. “[T]his projection of increased demand is due in part to the recent increased interest in the possible therapeutic uses of marijuana.”

According to a keyword search using the terms ‘smoked marijuana’ on the clinicaltrials.gov website, eight trials are presently ongoing to evaluate the plant’s effects in humans. Two of these trials are assessing the plant’s potential therapeutic efficacy.

New Study Tells Nothing About Marijuana’s Role in Heart Disease

April 24th, 2014

A new study on marijuana appeared in Journal of the American Heart Association. These are interesting data, but we have to interpret them very carefully.

Sure, we know cannabis can raise heart rate briefly, but most users develop tolerance to the effect. We’ve also seen (in a much larger sample) that it doesn’t increase mortality rates even among survivors of heart attacks.

But the new study made the news anyway. Investigators specifically searched a French database where physicians are legally bound to report any drug-related case that they view as “leading to temporary or permanent functional incapacity or disability, to inpatient hospitalization or prolongation of existing hospitalization, to congenital anomalies, or to an immediate vital risk or death.”

They then looked for cannabis users and found a shade less than 2,000 in the past 5 years. It’s impossible to know what that number means without knowing the number of people these physicians saw or how many patients used cannabis and did not end up reported to this database.

They then found a whopping 35 of these who had cardiac complications. It is impossible to know what to make of this number without knowing the number of cannabis users in France, which the authors report is 1.2 million. If you divide 35 by 1.2 million you get roughly .00003. I’m guessing that not all these cannabis users went to the doctor and not every person who used cannabis and had cardiac complications fessed up to the doctor, so let’s say that we’re off by two orders of magnitude. Let’s give the prohibitionists the benefit of the doubt and multiply by 100. That’d put the rate of problems up to .003.

If those are the chances of having cardiac complications as a French cannabis user, my first thought is that using cannabis protects people from cardiac problems. We need a comparison group of people who don’t use cannabis to know their rate of cardiac problems, but, as the authors point out, we simply don’t have those data. The closest estimates were 57 per 10,000 people, based on another study, which is .0057, or almost twice as bad as the rate among the cannabis users (after our generous overestimation). I’m not going to hold my breath for the the headline, “Cut your heart disease in half with cannabis.”

In short, this study tells us a lot about what kinds of cardiac complications appeared in people who were reported to the French government for cannabis-related problems, but tells us little about the link between cannabis use and cardiovascular disease.
?

Study: Medical Cannabis Laws Not Associated With Increased Use By Adolescents

April 22nd, 2014

The enactment of state laws legalizing the physician-recommended use of cannabis therapy is not associated with increased levels of marijuana use by young people, according to data published online in the Journal of Adolescent Health.

Researchers at Rhode Island Hospital and Brown University assessed the impact of medical cannabis laws by examining trends in reported drug use by high-schoolers in a cohort of states before and after legalization. Researchers compared these trends to geographically matched states that had not adopted medical marijuana laws.

Authors reported overall “no statistically significant differences in marijuana use before and after policy change for any state pairing,” and acknowledged that some states that had adopted medical cannabis laws experienced a decrease in adolescent’s self-reported use of the plant. “In the regression analysis, we did not find an overall increased probability of marijuana use related to the policy change,” they stated.

Investigators concluded, “This study did not find increases in adolescent marijuana use related to legalization of medical marijuana. … This suggests that concerns about ‘sending the wrong message’ may have been overblown. … Our study … may provide some reassurance to policy makers who wish to balance compassion for individuals who have been unable to find relief from conventional medical therapies with the safety and well-being of youth.”

A 2013 study published in the American Journal of Public Health similarly concluded that the passage of medical marijuana laws in various states has had no “statistically significant … effect on the prevalence of either lifetime or 30-day marijuana use” by adolescents residing in those states.

A 2012 study by researchers at McGill University in Montreal reported: “[P]assing MMLs (medical marijuana laws) decreased past-month use among adolescents … and had no discernible effect on the perceived riskiness of monthly use. … [These] estimates suggest that reported adolescent marijuana use may actually decrease following the passing of medical marijuana laws.”

Read the abstract of this latest study, “The Impact of State Medical Marijuana Legislation on Adolescent Marijuana Use,” online here.

Minnesota: African Americans Six Times More Likely Than Whites To Be Arrested For Marijuana Possession

April 21st, 2014

African Americans are arrested for marijuana possession offenses in Minnesota at a rate that is more than six-times higher than that of Caucasians, according to an analysis of 2011 FBI arrest data released today by the nonpartisan think-tank Minnesota 2020 and commissioned in part by Minnesota NORML.

Although African Americans comprise less than six percent of the state’s population, they represented over 27 percent of those persons arrested for violating marijuana possession laws in 2011. By comparison, whites comprise some 87 percent of the state’s population and constituted 69 percent of those arrested for violating marijuana possession laws. “Thus, the black arrest rate for marijuana possession was 687 and the white arrest rate was 107, making blacks 6.4 times more likely to be arrested for marijuana possession than whites,” the study found.

In 2010, blacks in Minnesota were arrested for cannabis possession at 7.8 times the rate of whites. Both African Americans and Caucasians consume cannabis at approximately similar rates.

The racial disparity in Minnesota in marijuana possession arrests is significantly higher than the national average. According to a 2013 analysis of marijuana possession arrests by race in 945 counties nationwide, blacks are approximately four times as likely as whites to be arrested for marijuana possession.

“[This] kind of over-representation cannot be accounted for without racial bias,” Minnesota 2020 Executive Director Steve Fletcher said today at a press conference. “It means black Minnesotans are bearing a disproportionate share of the personal and collateral costs of our war on drugs.”

A variety of factors contribute to the disparity in arrest rates, the study found. These include “over-policing in communities of color, cultural differences in where or how marijuana is used and purchased, and [the prevalence] of grants and seizure policies that incentivize volume over quality in drug arrests,” the think-tank acknowledged in a press release.

The report estimated that the collateral costs of a low-level marijuana arrest may total as much as $76,000 over the course of a decade, including attorney fees, fines, costs associated with attending mandatory drug treatment, lost income and job prospects, and barriers to public assistance and federal aid.

“In light of these human and financial costs, Minnesota lawmakers and law enforcement officials have a responsibility to consider whether marijuana possession laws in their current conception are actually contributing to public safety, or if they are instead producing undue hardship for individuals and growing inequities within society,” the study concludes.

Full text of the study, entitled “Collateral Costs: Racial Disparities and Injustice in Minnesota’s Marijuana Laws,” is available online here.

NORML Responds To Latest Media Frenzy Over Pot and ‘Brain Damage’ Fears

April 18th, 2014

The mainstream media launched into a reefer mad frenzy this week after researchers from Harvard University in Boston and Northwestern University in Chicago published the results of a neuroimaging study assessing the brains of a small cohort of regular marijuana smokers and non-users. The brain scans identified various differences between the two groups in three aspects of brain morphometry: gray matter density, volume, and shape. These differences triggered dozens of high-profile media outlets to lose their collective minds. Here’s a sampling:

CNN: Casual marijuana use may damage your brain

Financial Post: Study proves occasional marijuana use is mind altering

Time: Recreational pot use harmful to young people’s brains

International Business Times: Casual Marijuana Smoking at Young Age May Cause Irreparable Brain Damage – Even at One Joint Per Week

UK Telegraph: Smoking cannabis will change you. That’s not a ‘risk’, it’s a certainty

Yet despite the sensationalist headlines, the study itself was hardly newsworthy. Decades of research pertaining to the potential residual adverse effects of cannabis on brain cognition have failed to support the notion that marijuana poses any sort of permanent brain deficits. And as I write today on Alternet.org, this study similarly failed to report any sort of real-world adverse consequences associated with cannabis use:

Why the Media’s Fear-Mongering on Marijuana Effects on the Brain Is Faulty
via Alternet.org

[excerpt] Using high–resolution MRI imaging, scientists identified specific changes in particular regions of the brain that they inferred were likely due to marijuana exposure. (Since researchers only performed a single MRI session, they could not say definitively whether these changes were, in fact, caused by cannabis or whether they existed prior to subjects’ use of the plant.) Notably, however, these changes did not appear to be associated with any overt adverse effects in subjects’ actual cognition or behavior. (Separate studies assessing youth use of legal intoxicants, such as nicotine and alcohol, have also been associated with documented changes in brain structure. Ditto for caffeine intake in preclinical models. These findings have received far less media attention.)

Both the cases (20 marijuana users) and controls (20 nonusers) in the study were recruited from local universities, undermining the notion that the alleged ‘brain damaged potheads’ were any more academically challenged than their non-using peers. Further, as summarized by HealthDay: “Psychiatric interviews revealed that the pot smokers did not meet criteria for drug dependence. For example, marijuana use did not interfere with their studies, work or other activities, and they had not needed to increase the amount they used to get the same high.”

In other words, case subjects and controls appeared to function similarly in their professional and academic endeavors.

You can read the full text of my response here.

[Update: I have a separate op/ed ("Smoke weed, turn into a pothead? Not so fast") responding to this paper online in The Los Angeles Times here.]

Fortunately, my critique of this latest paper — and in particular the mainstream media’s sensationalist and erroneous coverage of its findings — is far from the only one. Below are links to several other excellent analyses:

MedPage Today: Striking a Nerve: Bungling the Cannabis Story

Daily Beast: No, Weed Won’t Rot Your Brain

Bits of DNA (blog): Does researching casual marijuana use cause brain abnormalities?

DPA Blog: Does Smoking Dope Really Make You a Dope?

Neuropsychological Deficits: Fact and Artifact About Marijuana Tests

April 15th, 2014

By Mitch Earleywine, Ph.D
State University of New York at Albany
Chair, NORML board of directors

A new study claims to show small deficits on neuropsychological tests in college students who started smoking marijuana early in life. It might get a lot of press. Prohibitionists love to bang the drum of marijuana-related cognitive deficits, so I’d like NORMLites to know how to make sense of this sort of research. The recurring themes in this literature involve several alternative explanations that never seem to dawn on journalists. These results often arise from artifacts of the study rather than physiological effects of the plant. I’d like to focus on a few: other drug use, dozens of statistical tests, the incentives for performance, and the demands communicated by the experimenters.NWA Canada Prohibition Car

The latest paper of this type is actually pretty good. Researchers studied over 30 people aged 18-20 who started using before age 17 (their average starting age was around 15) and who smoked at least 5 days per week for at least a year. They compared them to a comparable bunch of non-users. I hate to see 15-year-olds using anything psychoactive, even caffeine. Spending full days in high school with less than optimal memory functioning is no way to lay the groundwork for a superb life. I admit that I want these same people to grow up and be the next generation of activists, so feel free to call me selfish when I emphasize NORML’s consistent message: THE PLANT IS NOT FOR KIDS WHO LACK MEDICAL NECESSITY.

OTHER DRUG USE?
First, we have to keep other drug use in mind. Unfortunately, the marijuana group in this study got drunk more than 4 times as much in the last six months as the controls. Given what we know about binge drinking and neuropsychological functioning, it’s going to be hard to attribute any differences between these groups to the plant. It’s just as likely that any deficits stem from pounding beers. Studying cannabis users who aren’t so involved with alcohol would help address neuropsychological functioning much better.

HOW MANY TESTS?
In addition, we should always consider the number of measures in any study. Many of these neuropsychological tasks have multiple trials that can be scored multiple ways. The more statistical tests you run, the more likely it is that you’ll find a statistically significant difference by chance. It’s kind of like flipping coins. It’s rare to flip four heads in a row. But if you flip a coin a thousand times, odds are high that somewhere in the list of a thousand results will be four heads in a row. These investigators got 48 different test scores out of the participants. You’d expect at least 2 of them to be significant just by chance. They found differences on 14 different scores, suggesting that something’s going on, but we’re not sure which results are the “real” differences and which ones arose by accident. (That’s why we replicate studies like this.) And, as I mentioned, it might all be because of the booze.

WHY WOULD ANYONE DO ALL THESE TESTS?
We also have to consider incentives for performance. Most researchers bring participants to the lab for a fixed fee and ask them to crank out a bunch of crazy puzzles and memory assessments. It’s unclear why people would feel compelled to strain their brains. The authors of this study were kind enough to mention some relevant work by my friend (and former student) Dr. Rayna Macher. Dr. Macher showed that cannabis users respond best when you make the effort worth their while. She focused on people who used the plant at least four times per week for a year or more. She read one group some standard instructions for a memory test. The other group got the regular instructions plus an additional sentence: “It is important that you try your very best on these tasks, because this research will be used to support legislation on marijuana policy.”

As you’d guess, this simple sentence fired them up. Compared to cannabis users who didn’t hear that sentence, they performed better on 3 out of 10 measures. (You’d expect less than one difference by chance.) And compared to the non-users, the folks who got the incentive sentence did just as well on all the tests. For those who didn’t hear the incentive sentence, users did less well than non-users on 1 of the 10.

I know that prohibitionists are going to try to call this amotivation. (See my rant on that when you get a chance) I call it putting effort where it pays. But given what we know about how these studies can hamper the reform of marijuana laws, users everywhere should do their best on all tests whenever they get the chance.

WE OFTEN DO WHAT EXPERIMENTERS EXPECT OF US
Last but not least, we have to consider the demands communicated by the experimenter. Decades of data now support the idea that people often do what others expect them to do, especially if they believe the expectation, too. Another friend and former student, Dr. Alison Looby De Young, showed that these expectations are critical in studies of neuropsychological performance and cannabis. She gave a neuropsychological battery to men who had used cannabis at least three times per week for the last two years. One group of men read instructions that said that cannabis had no impact on their performance on these tests. Another group read instructions that said that cannabis was going to make them perform poorly. You guessed it, those men who heard they were going to flub the tests performed worse on 2 of the 4 tests. (You’d expect less than one difference by chance). As you might imagine, some laboratories communicate their expectations about cannabis and cognitive function subtly or not so subtly. Some participants are bound to behave accordingly. So what looks like a cognitive deficit is just an artifact of the laboratory environment where experimenters stare daggers at cannabis users.

In the end, I’m glad that researchers do this work, but these effects are too small and fleeting to justify prohibition. We already know that cannabis isn’t for healthy kids. People who get heavily involved with the plant early in life might not perform as well as those who never touch cannabis even if investigators control for other drug use, AND use a sensible number of tests, AND provide appropriate incentives, AND communicate a reasonable expectation.

But how many people should go to jail for that?

If you said, “None,” you’ve done an excellent job on an important cognitive test.

Study: Frequent Cannabis Consumers Less Likely To Engage In Problematic Alcohol Use

April 15th, 2014

Those who report consuming cannabis two or three times per week are less likely to engage in at risk drinking behavior, according to data published online in The American Journal of Addictions.

Investigators from Sweden’s Lund University, Department of Clinical Sciences, analyzed data from a nationwide survey on alcohol and drug use conducted by the National Institute of Public Health. Over 22,000 respondents between the ages of 15 and 64 participated in the survey.

Researchers reported that frequent cannabis consumers (defined as having used cannabis two or three times per week) were less likely to engage in hazardous drinking practices compared to infrequent users (those who reported having consumed cannabis fewer than four times per month).

They concluded: “In the present study, it has been shown that, in the Swedish general population, cannabis use is associated with a higher prevalence of other illicit drug use and hazardous alcohol use. Among cannabis users, frequent cannabis use is associated with a higher prevalence of other illicit drug use and a lower prevalence of hazardous alcohol use when compared to occasional cannabis use. … … The inverse relationship between the frequency of cannabis use and hazardous drinking has not been reported before to our knowledge. … This may indicate that cannabis users and alcohol users are different groups, albeit with a high degree of overlap between groups, with different characteristics and clinical needs.”

A review paper published in February in the journal Alcohol and Alcoholism similarly acknowledged that some cannabis consumers likely substitute the plant for alcohol. It concluded: “While more research and improved study designs are needed to better identify the extent and impact of cannabis substitution on those affected by AUD (alcohol use disorders), cannabis does appear to be a potential substitute for alcohol. Perhaps more importantly, cannabis is both safer and potentially less addictive than benzodiazepines and other pharmaceuticals that have been evaluated as substitutes for alcohol.”

An abstract of the study, “Alcohol and drug use in groups of cannabis users: Results from a survey on drug use in the Swedish general population,” appears here.

Study: Enactment Of Medical Cannabis Laws Not Associated With Higher Crime Rates

April 8th, 2014

The enactment of medicinal cannabis laws is not associated with any rise in statewide criminal activity and may even be related to reductions in incidences of violent crime, according to data published online in the journal PLoS ONE.

Researchers at the University of Texas at Dallas tracked crime rates across all 50 states between the years between 1990 and 2006, a time period during which 11 states legalized marijuana for medical use. Authors reviewed FBI data to determine whether there existed any association between the passage of medicinal cannabis laws and varying rates of statewide criminal activity, specifically reported crimes of homicide, rape, robbery, assault, burglary, larceny, and auto theft.

Investigators reported that the passage of medical marijuana laws was not associated with an increase in any of the seven crime types assessed, but that liberalized laws were associated with decreases in certain types of violent crime.

“The central finding gleaned from the present study was that MML (medical marijuana legalization) is not predictive of higher crime rates and may be related to reductions in rates of homicide and assault,” authors reported. “Interestingly, robbery and burglary rates were unaffected by medicinal marijuana legislation, which runs counter to the claim that dispensaries and grow houses lead to an increase in victimization due to the opportunity structures linked to the amount of drugs and cash that are present. Although, this is in line with prior research suggesting that medical marijuana dispensaries may actually reduce crime in the immediate vicinity.”

Researchers concluded: “Medical marijuana laws were not found to have a crime exacerbating effect on any of the seven crime types. On the contrary, our findings indicated that MML precedes a reduction in homicide and assault. … In sum, these 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.”

Full text of the study, “The Effect of Medical Marijuana Laws on Crime: Evidence from State Panel Data, 1990-2006,” appears online here.