Cannabis is one of the oldest medicines on the planet, but predispositions for and against the plant tend to taint everything the public hears about its supposed benefits and dangers. Moreover, opinions on medical cannabis can be extreme. Countless parents, desperate to help a child dying from a hundred-plus seizures per day, relocated to states that legalized medical cannabis. This led to the term “medical marijuana refugees.” Yet, some who hear of such plans report the parents to law enforcement, and child services “save” the children by stripping them from their parents. Sadly, that is how extreme the medical cannabis fight has become, and it complicates clinical research like few compounds in history. Bias is one of many reasons it is difficult to judge cannabis studies, as are the following four examples.
1. Media Clickbait
In July 2016, The Journal of the American Medical Association Psychiatry published a study using data from the long-term Dunedin study in New Zealand that examined the physical effects of long-term cannabis use. Its findings produced headlines like “Cannabis use associated with periodontal disease” (American Dental Association) and “Long-Term Pot Use Tied to Gum Disease in Study” (Health Day). So, what did the study actually say? Using Dunedin tracking data that goes back more than two decades, the authors concluded that chronic cannabis consumers had equal or better physical health in all metrics except for gum health, making cannabis as bad for you as not flossing yet beneficial in other healthy ways. Moreover, the actual cause of the gum disease could be chronic smokers who, after smoking each night, regularly neglect dental hygiene regimens, which suggest no direct link between cannabis and gum health.
Now re-read the headlines above. They might be good clickbait, but they do not accurately reflect the main findings of the study, and they promote the stigmatization of a medically viable plant among individuals who often only read headlines. This epitomizes the difficulty in trusting the media to summarize health studies properly.
2. Conflicting Conclusions
The study referenced above also highlights how complex and contradictory findings can be. While most anti-cannabis advocates would never quote the positive findings in that study, they are all too quick to embrace the findings in another study by the same lead researcher, Dr. Madeline Meier. Four years earlier, she led a similar team who used Dunedin data to conclude that early cannabis use leads to permanent neuropsychological decline and the potential loss of IQ points (eight points on average). To this day, anti-cannabis advocates regularly quote these findings from the 2012 Proceedings of the National Academy of Sciences of the United States of America study, yet the story doesn’t end here.
Nine months after the 2012 Proceedings study, a different group of researchers published a rebuttal in the same journal that said socioeconomic status, not cannabis, was the likely cause. The authors wrote, “Although it would be too strong to say that the results [of the Meier study] have been discredited, the methodology is flawed and the causal inference drawn from the results premature.” In a press release for the study, the lead author added that wrongly blaming cannabis for serious health issues “may detract focus from and awareness on other potentially harmful behaviors.” An Oxford University reviewer reiterated the same conclusion, arguing, “The current focus on the alleged harms of cannabis may be obscuring the fact that its use is often correlated with that of other even more freely available drugs and possibly lifestyle factors. These may be as or more important than cannabis itself.”
Translation: People who wrongly blame cannabis for a host of evils are likely harming public health.
3. People Believe What They Want to Believe
In November 2016, this writer spoke with an anti-cannabis advocate who cited the 2012 study about IQ reduction, and when I mentioned the other studies, the person denied they even existed. I offered to send links, to which she countered, “I know it’s true no matter what the other studies say.” This anecdotal example is by no means rare when it comes to medical opinions on cannabis studies. There are many, many conflicting conclusions, and it is important to take all findings, for or against medical cannabis, with a grain of salt… but especially those studies that are against.
“There’s just so much noise and chatter because there’s so many harm studies being funded, much more so than benefit studies,” explains Dr. Sunil Aggarwal of Doctors for Cannabis Regulation (DFCR), speaking with PRØHBTD in 2016. “Just the sheer number where people are trying to justify harm—of course, there’s risks for cannabis use, just like there’s risk for any substance use. When we’re talking about medical indications, we stand with many of our colleagues in medicine who believe the evidence shows that cannabis does have bona fide, specific medical uses. It’s been proven by repeated, high-quality trials.”
Dr. Aggarwal stressed that not all studies are created equal, and laypeople sometimes give credence to journals that have poor impact ratings, meaning the studies are published in journals that not many people cite. He claims most cannabis studies in high-impact journals show that cannabis has strong medical potential, while more critical studies in low-impact journals often involve doctors with a stake in the addiction rehabilitation industry or who have other conflicts of interest. In other words, always put the author’s name through a search engine because you might be surprised what you find.
4. Correlation vs. Causation
The Drug Enforcement Administration (DEA) severely limits studies involving the cannabis plant and its natural compounds, which makes it difficult to conduct the type of large-scale, double-blind, peer-reviewed studies that generally produce the most reliable findings. For this reason, many studies involve self-reporting surveys and statistical analysis that might show correlations between cannabis and certain health risks or disorders; however, many people are too quick to conflate correlation with causation. This recalls the famous statistician phrase “correlation does not imply causation” to stress that a correlation (i.e., a mutual relationship or connection) between two variables does not imply that one causes the other.
For example, some people in the 19th century noted that an increase in radios corresponded with an increase in the number of people in insane asylums, which is obviously not possible since Yanni wasn’t around back then. When it comes to observational cannabis studies, the data might show high rates of mental health disorders among people who actively smoke cannabis, but that does not mean cannabis caused the problem. Rather, the disorder might have motivated self-medicating cannabis (or other substance) use. Consider this: A 2010 study in Depression and Anxiety found that 20 percent of individuals with post-traumatic stress disorder (PTSD) self-medicated with drugs and/or alcohol. Likewise, the National Center for PTSD notes that cannabis-use rates are much higher for PTSD-afflicted veterans, but most people would hopefully agree that traumatic conflict, not cannabis, typically caused the PTSD .
Maybe this is a better example: A 2013 study in Schizophrenia Research compared the cognitive skills of psychosis patients who use and don’t use cannabis. The findings? “Patients who had ever smoked cannabis had significantly higher current and premorbid IQ compared to patients who had never used cannabis.” In other words, if associated traits imply causation, smoking cannabis makes people significantly smarter.
What To Do
Take everything with a grain of salt. Don’t just read headlines. Double-check the credibility of the author. If unfamiliar with the media source, check for bias. Always search the clinical journals for alternative findings. Consider all the different correlations before trying to determine the individual or collective cause of the problem. Understand that cannabis is a divisive issue, and even legitimate researchers can publish findings that unintentionally reflect an anti-cannabis bias. Use basic common sense. Write the DEA and demand that it reschedule cannabis to allow for more comprehensive research.
Image: Kyle Butler, CC-BY
David Jenison is a Los Angeles native and the editor-in-chief of PROHBTD. He has covered entertainment, restaurants and travel for more than 20 years.