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Home » Part 1. Marijuana and medicine assessing the science

Part 1. Marijuana and medicine assessing the science

Last updated on September 14th, 2020 at 12:03 pm

I suspect, like legal same sex marriage, social norms are changing across the USA (and the world), which has lead to the decriminalization of marijuana in 23 states and the District of Columbia for some medical conditions. The US Federal Government, has shown little enthusiasm in enforcing Federal law about cannabis, although the Federal government retains the highest authority in regulating certain drugs like marijuana. So let’s look at marijuana and medicine assessing the science critically.

It’s clear that rational people still want regulations for marijuana, including prohibitions against public smoking (I don’t want second hand cannabis smoke wafting over me or my children, as much as I don’t want to inhale other people’s tobacco smoke). And a safe society would have strict regulations that would forbid marijuana smoking by individuals who have roles in public health and safety like physicians, pilots, mass transit drivers, and others.

But I think those would be reasonable boundaries for legalization of cannabis that would be reasonable to most people. But this is not the point of this article.

As the push to legalize marijuana for personal or medical use gains traction in the USA, there has developed a strong belief, unsupported by evidence, of the value of the medical uses of cannabis. What is troublesome is that the pro-marijuana side seems to make claims about the medical uses of cannabis that appear to be only tenuously supported by real scientific evidence.

In fact, some of the claims are downright dangerous. The reasons for pushing this is probably, though I can only speculate, to make it appear that marijuana is some miracle product, so let’s speed up the legalization of it. It’s like the Food Babe telling us that kale is the miracle food, except that kale isn’t illegal. It does taste awful (but again, not the point).

Because of the amount of scientific information, this article is part 1 of a 5-part series about marijuana and medicine – assessing the science. For detailed analysis of various aspects of the science of marijuana and medicine, check out each of the subtopics:

Part 2 – Marijuana and cancer
Part 3 – Marijuana and neurological disorders
Part 4 – Marijuana health risks
Part 5 – Summary of marijuana and medicine



On the internet, you will find numerous memes, blog posts, and even mainstream articles that claim that smoking pot, eating pot, rubbing hemp oil (which is manufactured from the seeds of cannabis plants that don’t contain much THC, or tetrahydrocannabinol, the active hallucinogenic agent of cannabis), or doing something with all or a part of a cannabis plant will cure or prevent some disease–most of the claims seem to be about cancer, though not exclusively.

Famously, marijuana has been used as an anti-emitic to ameliorate or mitigate nausea and vomiting after radiotherapy and chemotherapy in cancer treatment. In fact, marijuana has been smuggled into some cancer wards since the late 1930’s.

Unfortunately, even with this particular use of cannabis, there have been negative results in some well designed clinical trials and positive results in some others. The highly variable result may result from the difficulty of trial design to biases of patients and researchers to a huge dose of the placebo effect, an effect that many scientists have concluded is overrated.

But even as an anti-emitic, marijuana has no curative power, it’s a palliative treatment for the nasty side effects of chemotherapy and radiotherapy in the treatment of cancer. Since weight loss and wasting are side-effects of cancer treatments, any medication that can prevent the nausea and vomiting can lead to better medical and lifestyle outcomes in cancer treatment.

If there is a real clinical difference between those who use marijuana vs. those who don’t for cancer therapy effects, we need real clinical trials that show the difference. Moreover, to do this type of clinical research correctly we require real dosage information, that is, at what dose do we get the best effect. This would be a landmark study, and until then, all we have are anecdotes, albeit emotional ones.

Marijuana and medicine assessing the science


Is there any evidence out there that actually support a hypothesis that  cannabis or its byproducts have any effect on any medical condition?

So before I head down the the road of whether THC or cannabis has any effect on any particular disease, I’m not going to play the argument from ignorance. If there isn’t any evidence that marijuana or THC cures a particular cancer (or any disease), then that means there’s no evidence.

For example, I don’t have evidence that there are no pink unicorns walking on Mars, but I’m fairly certain of it. If I am certain that unicorns don’t exist, that there are no pink versions of unicorns, and that there’s not enough atmosphere on Mars to allow the survival of unicorns, then we have enough biological plausibility (or, in this case, lack thereof) to state that there are no pink unicorns on Mars.

Of course, someone will then state that there’s a secret cavern that is filled with oxygen and organic, GMO-free foods for a hidden population of pink unicorns. There’s no winning when it comes to the argument from ignorance, because it’s a moving target. This is why science generally does not attempt to “prove” a negative, in this case, that there are no pink unicorns on Mars, and why proper science demands extraordinary evidence to support extraordinary claims. If there are pink unicorns on Mars, bring real evidence.

So it’s a logical fallacy to claim that “no one has never researched smoking weed on reduced brain cancer, so you don’t know if it does.” Nope, I don’t do those kind of arguments. If there is no evidence that smoking cannabis cures brain cancer, we cannot claim that it might cure brain cancer.



Finally, the only thing that matters in science and medicine is evidence. More than that, the quantity and quality of evidence matters. One small study in one minor journal that includes 10 patients is not good evidence. It barely qualifies as evidence, bad, good or otherwise.

And more recent published evidence takes priority over older publications. Why? Because if something was “uncovered” 20 years ago, and has never been repeated, never been a part of the consensus, then what value does it have?

Finally, there is a hierarchy of evidence. At the bottom is junk science published in anti-science websites like Natural news. Even real science, which might show cannabis effects on cell cultures, fall far far below a systematic review double blinded, randomized clinical trials that actually show a statistically significant clinical effect. Over 90% of scientific results that are breathlessly advertised never become anything important in medicine, mainly because they fail in clinical trials.


Editor’s note: This article is a substantial update of an article that was originally published in April 2014. It has been completely revised and updated to include more comprehensive information, to improve readability and to add current research. I’ve also sub-divided into five separate articles to improve readability, and to allow a reader to choose the marijuana and medicine article that is of highest interest.

Another editor’s note: I have a policy of open commenting and dissent to my articles. I only delete spam, racism, and just random nonsense. Please comment here if you wish, because I know everyone has an opinion on marijuana. But ad hominem hatred, strawman arguments and other logical fallacies will be mocked–bring high quality, peer-reviewed evidence. I might even rewrite or add another section if it’s high quality and peer-reviewed.

Michael Simpson

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