Medical marijuana, glaucoma, and why I don’t tell people what I study
When I talk about my work with non-colleagues, I typically don’t disclose that I work with the endocannabinoid system.
Even though my research doesn’t involve marijuana, or even its psychoactive compound (∆9-THC), as soon as anything with the “cannabi-” root is mentioned, I feel like people suddenly judge me as a “pusher” of “medical” marijuana. Instead of seeing me as someone who is trying to better understand disease and find new ways to treat it, I worry that I will be perceived as a “stoner” trying to validate access and use of a recreational substance in the guise of “medical” compound. This perception bothers me, and I feel like it takes away from the important work a lot of researchers are doing.
I think that a lot of the general public’s skepticism about the use of medical marijuana stems from perception of whether or not marijuana is actually needed to treat the diseases in which people claim they use it for. And even if it does “treat” the disease, whether or not it’s the best and most effective way to do so.
Skepticism about the “medical” use and effectiveness of medical marijuana isn’t unwarranted.
In fact, a recent meta-analysis highlighted the lack of evidence to support the use of medical marijuana in a wide number of medical indications. The authors of this study found that there was only “moderate-quality” evidence supporting the use in chronic pain and spasticity. Other indications simply did not have enough data to support claims of effectiveness. There are many problems that could have contributed to this lack of “good quality” evidence, but I feel there are two major issues which are especially important to consider in research involving medical marijuana: numbers and reproducibility of the effect.
1 Numbers — The gold standard in evaluating the effectiveness of drugs is through randomized clinical trials. In the previously mentioned meta-analysis by Whiting et al., only 7 reports of using the Cannabis plant were designed and controlled appropriately enough to be considered in the analysis (all of the other 498 reports used either synthetic or purified cannabinoids, or were excluded for not having sufficient power, controls, etc.). There could be several factors which might influence why these types of studies are so few in number, including regulatory barriers making access to the drugs difficult, difficulty getting funding, and getting sufficient patient participation. For these reasons, researchers are less inclined to want to study use of these compounds, especially in clinical settings.
2 Reproducibility — The amount of active ingredients in marijuana, like in any other plant, vary depending on the conditions they’re grown in. That means depending on the strain of the plant, the location (ie, soil conditions, weather), and the season of the year (ie, amount of sunlight, outside temperature) the levels of active ingredients can vary drastically. Even for large clinical trials, it would be difficult to obtain enough marijuana with the exact same levels of active ingredients, let alone be available to reproduce this effect over and over again to prove efficacy in subsequent trials. It would be unreasonable to expect that those who may later be prescribed medical marijuana could have access to the same level of active ingredients. Luckily, at least in Canada, there is now mandatory reporting of at least two active ingredients in produced marijuana (∆9-THC, the psychoactive component, and cannabidiol, also known as CBD — a non-psychoactive component). However, the fact that these are reported does not mean that the same “dose” may be achieved.
So why are there so many vocal groups who are so adamant about having access to medical marijuana, even though there isn’t a large number of good studies to back it up?
By acquiring the drug (albeit illegally), people get to “test” the drug even though not on the market. Once people start “testing” it on themselves, anecdotal evidence is reported and spread, and then others want to try the drug for themselves. Sometimes this evidence is useful and fuels research, but, there are also instances where anecdotal data doesn’t hold up, or simply isn’t true anymore.
When I’ve talked about medical marijuana with others, even before starting graduate school, the first use that is usually mentioned is glaucoma.
Even if those I’m talking to don’t support the use of “medical” marijuana, they still name glaucoma as a disease which marijuana is used to treat. This common perception is a good example of the discrepancies between general perception and scientific data. While there are presently 16 states in the US where medical marijuana is available for use in glaucoma, currently, the Canadian and American ophthalmological societies do not support the use for this indication. Then why do people assume that medical marijuana is used for this purpose? Maybe it’s because the first person to legally possess medical marijuana in the US (Robert Randall in 1976), acquired it to treat his glaucoma.
Ocular hypertension is the only modifiable risk factor for glaucoma, and what your eye doctor tests for when you annoyingly get air puffed onto your eye. The first study reporting an effect of inhaled marijuana on intraocular pressure was one by Hepler and Frank in 1971, published in the Journal of the American Medical Association. This study was promising, as at that time, there were very few other glaucoma drugs available, most of which had some nasty side effects. However since then, not only have we developed better drugs to lower intraocular pressure, we’ve realized that inhaling marijuana only decreases pressure for a few hours (for example, a small human study showed maximum reduction 60-90 mins after inhalation, with a complete loss of effect at 4 hours). This would mean that one would have to smoke a lot of marijuana to have the same intraocular pressure lowering effect as many of the currently available therapeutics (latanoprost, for example, which only has to be taken once per day). Not only does the effect not last that long, any effect that it does have, can disappear with repeated administration (see here and here).
In most countries (including Canada), in order for a drug to be approved as a therapeutic, it must be efficacious and present low risk/benefit ratio in clinical trials (see Canada’s Food and Drug Regulations, Section C). Moreover, in order to become a standard in clinical practice, the drug must demonstrate benefit over currently available therapeutics. So while glaucoma might have been an indication for medical marijuana initially, we currently don’t have enough data to support its use as an intraocular pressure lowering drug when compared with other current therapies. This is why the ophthalmological societies don’t support its use. This isn’t to say that study of all cannabinoids for this purpose (and others) isn’t unwarranted. In fact, my PhD research currently involves testing compounds which modify the endocannabinoid system to help treat glaucoma.
The discrepancy between public opinion and scientific data leads to spreading of misinformation and skepticism.
To illustrate how this might arise, let’s suppose that “John” is talking to his ophthalmologist (“Dr. O”) about potential therapies for his newly diagnosed ocular hypertension.
John then leaves the appointment assuming that since his ophthalmologist didn’t want to prescribe medical marijuana for the thing he thought it was most useful for, that maybe all medical marijuana isn’t really effective, and therefore maybe people just want it for recreational use.
But, it isn’t just the general public who is skeptical about medical marijuana, there are a lot of physicians, scientists, and policy makers who have their reservations, too, again fueled by the lack of good data, and spreading of misinformation.
This is the main reason I don’t tell people what I do. Because there’s a lot of misinformation out there, and people become skeptical of your intentions. In fact, this is one reason why I agreed to participate in this blog; to contribute to a source where credible information can be accessed and discussed.
Next time, I’ll tell you more about endocannabinoids and synthetic cannabinoids, and the types of research people are doing with these compounds. And discuss why, even with the lack of evidence in some areas, cannabinoids are worth investigating.
