A just-published literature review assessing the potential adverse effects associated with habitual marijuana smoking has the mainstream media in a reefer mad frenzy. Predictably, however, the paper’s conclusions are far less sensational than the media headlines.
The review, authored by Australian professor and longtime cannabis researcher Wayne Hall, evaluates potential adverse health outcomes associated with “daily cannabis smoking.” These potential risks include dependence, increased likelihood of having an auto accident, and exacerbated mental health effects, among other possible outcomes. Yet, none of these claims are novel; nor are they particularly alarmist — particularly when placed in proper context.
For example, in regard to cannabis’ dependence liabilit, the author acknowledges: “The lifetime risk of developing dependence among those who have ever used cannabis was estimated at 9 percent in the United States … [compared to] 32 percent for nicotine, 23 percent for heroin, 17 percent for cocaine, 15 percent for alcohol, and 11 percent for stimulants.” Hall adds, “The adverse health and social consequences of cannabis use reported by cannabis users who seek treatment for dependence appear to be less severe than those reported by alcohol.”
Nonetheless, the October 7 headline from brietbart.com blared, “Cannabis as addictive as heroin, new study finds.” The reality, of course, is that Hall’s paper said nothing of the sort.
But breitbart’s reporting is par for the course. According to the lede of the New York Daily News, “Smoking marijuana can lead to mental disorders, car crashes, unhealthy babies and more problems, according to a major 20-year study.” But there is no new ‘study.’ Hall’s work is simply a selective literature review of previously published data. Further, the Daily News hyperbolic opening deliberately distorts what Hall’s paper actually says.
For example, Hall acknowledges that studies assessing marijuana use and prenatal development suffer from “a number of limitations” and typically do not satisfactorily “adjust for effects of major cofounders such as cigarette smoking.” (As for the News claim that maternal cannabis use causes “unhealthy babies,” Hall more conservatively speculates that this behavior is likely, at worst, to be associated with a “modest” reduction in birth weight.)
Hall is similarly cautious in regard to the claim that cannabis use ‘can lead to mental disorders,’ writing instead that evidence purporting to show a causal link between heavy pot use and schizophrenia is “mixed” and that evidence supporting the notion of cannabis as a trigger for depression is weak. As for claims that pot use triggers psychosis, Hall writes: “It is difficult to decide whether cannabis use has had any effects on psychosis incidence, because even if the relationship were causal, cannabis use would produce a very modest increase in incidence. The detection of any such increases is complicated by changes in diagnostic criteria and psychiatric services for psychosis, the poor quality of administrative data on the treated cases of psychosis, and possibly by social improvements that may have reduced incidence of psychosis during the period in which cannabis use increased.”
As for the idea that those under the influence of cannabis possess an increased risk of traffic accident, Hall cites a 2012 review finding that drivers acutely impaired by pot have a two-fold higher risk of crash as compared to sober drivers. (Other meta-analyses have reported that this estimate may be an overestimate of actual risk.) Nevertheless, Hall acknowledges that even a two-fold risk is far less than the risk associated with alcohol, which may increase one’s likelihood of accident 15-fold at a comparable intoxicating dose.
“The perception that cannabis is a safe drug is a mistaken reaction,” Hall states — as if anyone ever suggested that the herb was innocuous. By contrast, advocates for an end to cannabis’ criminal prohibition readily acknowledge that pot’s potential risks are not so significant to warrant the plant’s schedule I restrictive status under federal law — a federal classification that falsely presumes that marijuana’s potential harms are similar to those of heroin. And this fact remains unchanged. It makes no sense from a public health perspective, a fiscal perspective, or a moral perspective to perpetuate the prosecution and stigmatization of those adults who choose to responsibly consume a substance that is objectively safer than either alcohol or tobacco. To continue to criminalize the marijuana plant and to arrest and prosecute those adults who consume it responsibly is a disproportionate public policy response to what, at worst, is a public health concern, but not a criminal justice issue.