Feature

A Doctor Explains How Medical Studies Can Differ Wildly on Cannabis

By David Jenison

Former Surgeon General Joycelyn Elders says cannabis is not physically addictive, while Harvard Medical School professor Bertha Madras said “30 percent of current cannabis users harbor a use disorder” (or addiction) in the recent Washington Post editorial “5 Reasons Marijuana Is Not Medicine.” Obviously they cannot both be right, and this example of contradictory findings epitomizes the difficulty in analyzing medical studies about cannabis. To better navigate these murky medical waters, PRØHBTD asked Dr. Sunil Aggarwal of Doctors for Cannabis Regulation (DFCR) for help.

There are now countless clinical studies involving cannabis, but the findings could not be more different in calling the plant an aid or a danger. Why is there such a major divergence in research?

It really depends on what journals you're looking at and the quality of the studies. We live in a sea of information, so you have to apply filters and understand what data is warranted and valid, and what data is biased and poorly collected and analyzed. There are thousands and thousands of studies of cannabis and cannabinoids, with the pre-clinical, clinical, basic science and the whole range in between.

Let's filter them and, say, look specifically at cannabis in the use of clinical indications in which the studies are done in a randomized, double-blind, placebo-controlled format. If you take that filter, nearly every one of them is a positive outcome. That's a fact. There's no debate about that with the highest level of evidence with the best designed trials. Then if you break it down by pain indications, and if you say, "Okay, cannabis and cannabinoids, not just herbal cannabis,” and more than 70 percent are positive outcomes. If you do an experiment over and over again—different populations, different times, different locations, same material, similar conditions, chronic pain—seven out of 10 times it comes out positive. That's not a divergence. That's a convergence to efficacy.

There's just so much noise and chatter because there's so many harm studies being funded, much more so than benefit studies. 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.

Then if you expand to international studies, look at cannabis administered in oral forms, you're looking at studies involving hundreds and hundreds of patients simultaneously in multiple sites. That's an even higher bar in terms of testing. Those also show positive outcomes for the treatment of cancer-related pain, spasticity in multiple sclerosis, even reduction in the number of trips to the emergency room in a year. Those studies are getting bigger with longer durations and still showing positive outcomes, so I'm not buying that there's this big divergence. It's more of a convergence in specific indications and confusion over harm studies versus benefit studies.

As a layperson, when I'm scrolling through clinical journals, is there an easy way to tell if it is a legitimate or an esteemed journal?

Yeah, I mean this is a problem. We really are expecting the public to digest peer-reviewed medical research. It's not an easy thing, even to medical doctors, to fully get. It requires specialized understanding about quality of trials and quality of tests that are being applied. It really is something that requires some sophistication with medical science to evaluate. There are research journals that have poor impact ratings, meaning that they're published in journals that not many people cite. Those are standard metrics for the quality of a journal. Impact factors, they call them.

Some journals are not indexed by the National Library of Medicine. There's some global drug policy journal that published a lot of articles by Andrea Barthwell, folks like that who benefit from the marijuana abuse treatment industry. That journal is not indexed by the National Library of Medicine, but people cite from that as if it's a vetted journal. Those are the kind of things that you have to look for.

Then what kind of study is this? Are these static brain scans trying to imply causation for harm? Is this a prospective study over time that's trying to measure a particular relevant clinical outcome for patients? Those kind of things need to be judged. Then, of course, there's epidemiology where you are doing large studies in the population and trying to show associations between exposure and outcome. There's a whole lot there.

I would say the best thing to do is see if it makes common sense, see if it's being published in a reputable journal and then always have a look at who's funding the study.

Street art image by Skurktur.

 

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