Separating Fact from Fiction in the Cannabis Debate
By Dan Werb
Conversations about cannabis policy are heating up. So it’s no surprise that we suddenly seem immersed in claims and counterclaims on a slew of topics related to cannabis use and regulation.
Cannabis causes schizophrenia. Cannabis regulation leads to increased traffic fatalities. These are just some of the examples that seem to pop up, again and again, in news articles and online. They sound true, perhaps because they are repeated so many times, and also because they are often said to be based on scientific evidence.
In the UK, the Telegraph even ran the following headline: “Cannabis as addictive as heroin, major new study finds.” On its surface, this claim reads as if it were backed by scientific evidence. But is it?
The International Centre for Science in Drug Policy has tasked itself with determining the strength of scientific support for such claims. Over the past year, we’ve been working diligently on scanning the news media and online conversations about cannabis to identify the most oft-repeated or high-profile claims—including the ones above—related to its use and regulation.
We narrowed the list down to 13 by reviewing media reports, government announcements, and monitoring online discussion on cannabis. We then performed comprehensive scientific reviews of all of the relevant peer-reviewed published research. As our new reports explain, we found that not one of the claims was strongly supported by scientific evidence.
For example, the science does not, in fact, suggest that cannabis is as addictive as heroin. Rather, cannabis dependence is estimated to occur in less than one in ten people who use cannabis across their entire lifetimes. Rates of lifetime dependence to heroin, by contrast, are about one in four.
Does cannabis use cause schizophrenia? While studies have shown that cannabis use is associated with schizophrenia, this is a very different claim. Scientists suggest that people at risk of schizophrenia might actually use cannabis to mitigate early symptoms of the condition, and that this is the reason for the association. The claim, then, confuses correlation with causation.
Furthermore, if cannabis use caused schizophrenia, we would presumably see changes in schizophrenia rates based on levels of cannabis use. But during a period when cannabis use increased fourfold in the UK (1970–2010), the incidence of schizophrenia remained essentially stable.
Does cannabis regulation lead to more traffic fatalities as a result of people driving while stoned? In Colorado, recreational cannabis use and possession was regulated in 2012. Since then, traffic fatality rates have been below the yearly average seen over the past decade (i.e., since 2002). Of course, we don’t know what kind of traffic fatality rates we’ll see in the coming years in Colorado and other places that have regulated cannabis. But at present, there isn’t any evidence to suggest that regulating cannabis will lead to more people involved in deadly car crashes.
These are only a few of the examples reviewed in the reports. The main conclusion is that, for the most part, the global conversation around cannabis policy is mired in unscientific claims. And that can have serious consequences for the effectiveness—and potential harms—of cannabis policies in many countries.
In Canada, for instance, a federal election is set for the fall, and cannabis regulation has been front and center, with the current conservative government frequently advocating for a “tough on crime” approach. Tellingly, the Canadian government’s production of anticannabis public service announcements recently drew the ire of the country’s main physician group, the Canadian Medical Association, which refused to endorse the so-called “educational campaign” because it believed the ads were serving political—rather than educational—goals.
In the United States and elsewhere, third-party advocacy groups continue to spread disinformation about cannabis. Kevin Sabet, director of Smart Approaches to Marijuana, an antiregulation group, stated on CNN that cannabis “is a drug that can result [in] serious, long-term consequences, like schizophrenia,” a claim that, as described above, is not backed by science.
The dangers of masquerading falsities about cannabis as scientific evidence are serious: if the general public and our policymakers can’t distinguish between what is true or false, how can we expect to develop effective, evidence-based approaches to control cannabis?
Our new reports will help to separate fact from fiction. Given the rapid movement on cannabis regulation that we’re witnessing across the world, and the upcoming United Nations General Assembly Special Session on Drugs, it’s more important than ever to make sure the truth about cannabis use and regulation is publicly available.
The International Centre for Science in Drug Policy is a grantee of the Open Society Foundations.
Dan Werb is the director for the International Centre for Science in Drug Policy.