When I first started writing about the claims made for medical marijuana and the cannabis oil derived from it, it didn’t take long for me to characterize medical claims for cannabis as the “new herbalism,” as opposed to pharmacognosy, the branch of pharmacology devoted to the study of natural products. The reason is simple. Although I support legalization of marijuana for recreational use, when I look at how medical marijuana has been promoted as a “foot-in-the-door” prelude to legalization, I see testimonials and flimsy evidence ruling over all. I see all the hallmarks of alternative medicine herbalism and none of the hallmarks of pharmacology. Here’s what I mean. Pharmacognosy examines an herb, plant, or other natural product and seeks to identify the chemicals within it that have pharmacological activity against a condition or a disease, the better to purify and isolate those chemicals and turn them into drugs. Herbalism, on the other hand, emphasizes the use of whole plants or extracts from plants, rather than the isolation of the most active compounds. Thus, herbal remedies often contain hundreds, or even thousands, of different compounds, of which only one or a few are active. Even extracts, such as cannabis oil, contain many compounds.
In contrast to pharmacognosy, herbalists make the claim that whole herbs and plant components possess a synergy that is missing from the purified active constituents and/or that the mixture is safer than the pure components because one compound can reduce the side effects of another without reducing therapeutic efficacy. When looked at closely neither claim stands up to scrutiny. Synergism between plant constituents is rare and very difficult to demonstrate, for example. In essence, herbalism turns back the clock 200 years to a time before scientists had developed the techniques and abilities to isolate active ingredients with pharmaceutical activity. Moreover, herbalism, in contrast to pharmacognosy, emphasizes anecdotes over scientific evidence.
Indeed, in my previous posts in this series on medical marijuana, one theme has emerged, which is that cannabis—specifically, a class of active chemicals in marijuana known as cannabinoids—has potential for some diseases but is not the panacea claimed by its proponents. It does not cure cancer, for instance, contrary to glowing testimonials promoted by people like Rick Simpson. For other conditions, the evidence is either not particularly compelling or only mildly promising.
So I reacted with considerable dismay on Friday night when I saw this news report on the 11 o’clock news, “Michigan panel recommends allowing marijuana for autism“:
It’s been a while since I discussed medical marijuana, even though it’s a topic I’ve been meaning to come back to since I first dubbed medical marijuana to be the equivalent of herbalism and discussed how the potential of cannabinoids to treat cancer has been, thus far, unimpressive, with relatively modest antitumor effects. The reason I refer to medical marijuana as the “new herbalism” is because the arguments made in favor of medical marijuana are very much like arguments for herbalism, including arguments that using the natural plant is superior to using specific purified cannabinoids, appeals to how “natural” marijuana is, and claims of incredible effectiveness against all manner of diseases, including deadly diseases like cancer, based on anecdotes and testimonials. Now, as I pointed out before, not only am I not opposed to the legalization and regulation of marijuana for recreational use, even though I’ve never tried it myself, but I support it. What I do not support are claims for medical effects that are not backed up with good scientific evidence, and for medical marijuana most claims fall into that category. That’s why I tend to view medical marijuana as a backdoor way to get marijuana legalized. Personally I’d rather advocates of marijuana legalization drop the charade, argue for legalization, and stop with the medical nonsense.
The last time around, I discussed the evidence supporting claims that “cannabis cures cancer” and found them to be wanting based on science. I didn’t however, discuss the “cannabis cures cancer” testimonial machine that drives the claim that marijuana is useful for treating cancer; at least, I only touched on it by discussing briefly Rick Simpson, who claims that his hash oil cures approximately 70% of patients with terminal cancer and a published anecdote in which it was claimed that hemp oil was effective in treating acute lymphoblastic leukemia. (It wasn’t. At least, the evidence presented was not convincing.) Since then, I’ve wanted to revisit the topic of “cannabis cures cancer” testimonials, and, for whatever reason, now seems like a good time to do it.
About a month ago, I finally wrote the post I had been promising to write for months before about medical marijuana. At the time, I also promised that there would be follow-up posts. Like Dug the Dog seeing a squirrel, I kept running into other topics that kept me from revisiting the topic. However, over the past couple of weeks, the New York Times gave me just the little nudge I needed to come back and revisit the topic, first by openly advocating the legalization of marijuana, then by vastly overstating the potential medical benefits of pot (compare the NYT coverage with my post from a month ago), and finally this weekend by running a story lamenting the federal law that makes research into medical marijuana difficult in this country.
I stated my position on marijuana last time, which is that marijuana should be at least decriminalized or, preferably, legalized, taxed, and regulated, just like tobacco and alcohol. I also likened the cult of medical marijuana to the “new herbalism,” because it (1) vastly inflates the potential of medicinal uses of marijuana and (2) ascribes near-mystical powers to smoking or making extracts out of marijuana, rather than identifying and isolating constituents of the plant that might have medicinal value. All of this is very much like herbalism in alternative medicine. Indeed, promoting laws legalizing medicinal marijuana is such an obvious ploy to open the door to full legalization that some advocates don’t even bother to disingenuously deny it any more. Given that I tend to support legalization, as a physician this sort of deception irritates me. It also has consequences, particularly when overblown claims are made for what cannabis can do. Perhaps the best example of this is the claim that cannabis cures cancer, which pops up all over the Internet in memes such as the one in the image above.
A while ago, I wrote about how the Cleveland Clinic had recently opened a clinic that dispensed herbal medicine according to traditional Chinese medicine (TCM) practice. As regular readers of the SBM blog might expect, I was not particularly impressed or approving of this particular bit of infiltration of quackademic medicine into a major academic medical center, particularly given some of the amazingly pseudoscientific treatments espoused by the naturopath who was running the clinic. I also pointed out that, although herbalism is the most plausible (or perhaps I should say the least implausible) of modalities commonly associated with “complementary and alternative medicine” (CAM) or “integrative medicine”, it still exhibits a number of problems, the biggest of which is what I like to call either the delivery problem or the bioavailability problem. In brief, herbs, when they work, are adulterated drugs. The active ingredient is usually a minor constituent, embedded in thousands of other constituents that make up herbs, and it’s almost impossible to control lot-to-lot consistency with respect to content or active ingredients given how location, weather, soil conditions, rainfall, and many other factors can affect how the plants from which the medicines are extracted grow and therefore their chemical composition. To demonstrate the concept, I pointed out that it’s much safer and more predictable to administer digoxin to a patient who needs its activity on the heart than it would be for the patient to chew on some foxglove leaves, given that the therapeutic window (the difference between the doses needed to produce therapeutic effects and the lowest dose that will cause significant toxicity) is narrow.
Which brings me to medical marijuana, a.k.a. medical cannabis.