Want to know the federal government’s rationale for keeping pot criminally prohibited? Look no further than a review article in the June 5 edition of the New England Journal of Medicine.



The paper, titled “Adverse Health Effects of Marijuana Use,” and authored primarily by Nora Volkow, director of the US National Institute on Drug Abuse, lays out the federal case for keeping marijuana illegal. Predictably, it is far from convincing. Volkow’s review highlights a laundry list of supposed harms associated with the use of cannabis. But a closer inspection of these claims finds many of them to be specious at best.



For example, the NIDA director alleges that cannabis use, particularly by adolescents, is associated with brain alterations and lower IQ. However, the IQ study cited by Volkow in her review was publicly repudiated in a separate analysis of the same data. This followup paper, published in the Proceedings of the National Academy of Sciences, suggests that socioeconomics, not pot use, is responsible for differences in IQ and that cannabis’ “true effect [on intelligence quotient] could be zero.”

Moreover, although a handful of imaging studies have identified slight differences in the brains of cannabis users versus controls, investigators have cautioned that these results are correlations only. Researchers have further noted that these differences do not appear to be associated with any overt adverse effects in subjects’ actual cognition or behavior.

Finally, Volkow neglects to acknowledge that many legal products, such as nicotine and alcohol, have similarly been associated with changes in brain structure. She’s equally mum to the reality that teens will arguably have less access to pot than they have now in a legal environment where the retail sale of cannabis are limited to state-licensed stores and customers are limited to those over the age of 21.



NIDA’s chief plays equally fast and loose with allegations that pot is addictive, a claim she argues possesses a “high” overall level of confidence. Yet, investigators at the National Academy of Sciences Institute of Medicine and others have repeatedly played down pot’s potential dependence liability, noting that cannabis’ risk of dependence is far lower than that of alcohol or tobacco and, at worst, is on par with that of anxiolytic drugs. (Others have further argued that the criteria for determining cannabis dependence are inherently biased against pot smokers.) Concluded the Institute of Medicine in its comprehensive report, Marijuana and Medicine: Assessing the Science Base, “In summary, although few marijuana users develop dependence, some do. But they appear to be less likely to do so than users of other drugs (including alcohol and nicotine), and marijuana dependence appears to be less severe than dependence on other drugs.”



The often-repudiated claim that cannabis is a "gateway" to the use of other controlled substances is also prominently featured in Volkow’s screed. Yet, even NIDA’s director acknowledges that criminal drug prohibition, not pot exposure, is most likely responsible for why a minority of cannabis consumers eventually experiments with other illicit substances. “[A]n alternative explanation is that people who are more susceptible to drug-taking behavior are simply more likely to start with marijuana because of its accessibility and that their subsequent social interactions with other drug users would increase the probability that they would try other drugs.” Volkow also concedes that alcohol and nicotine, two substances that typically precede marijuana use, “can also be categorized as gateway drugs.” Unlike with cannabis, however, she does not call for outlawing cigarettes or beer.



Nora Volkow also cites pot’s alleged role in motor vehicle accidents as a justification for the plant’s continued prohibition. Recent marijuana smoking is “associated with substantial driving impairment,” Volkow writes. Yet, this conclusion is contradicted by federally sponsored research, including this study – which reported, “THC’s effects on driving performance appear relatively small” — and a later study that concluded, “The effects of low doses of THC … on … general driving proficiency are minimal when taken alone.”

While some separate studies have identified a slightly higher risk of accident associated with drivers who test positive for pot as compared to controls (Others have not.), a recent meta-analysis of 66 studies assessing drug positive drivers and crash risk concluded that marijuana-positive drivers possessed an odds-adjusted risk of traffic injury of 1.10 and an odds-adjusted risk of fatal accident of 1.26. This risk level was among the lowest of any drugs assessed by the study’s author and it was comparable to the odds ratio associated with penicillin (OR=1.12), anti-histamines (OR=1.12), and antidepressants (OR=1.35). To put cannabis’ odds ratios in context, a separate study published in January in the journal Injury Prevention reported that drivers with a BAC of 0.01 percent are "46 percent more likely (OR = 1.46) to be officially blamed for a crash than are the sober drivers they collide with."



Commenting to the media about her findings, Dr. Volkow said her review disproves the notion that pot possesses “no harmful effects.” Of course, those of us who argue in favor of ending cannabis criminalization never claimed this to be the case. Just like any mood-altering substance, cannabis poses potential risks to the user. But these potential risks to the individual and to society do not warrant its present Schedule I illicit status under federal law, a classification that improperly argues that the plant lacks any accepted therapeutic value and that its risks equal those of heroin. And nothing in Volkow’s latest review proves otherwise.



Ultimately, the health concerns about pot, such as those expressed in the latest issue of the New England Journal of Medicine, are best addressed via regulation, age-restrictions, and public education, not by the imposition of criminalization, arrest, prosecution, and incarceration.

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