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Home » Part 4. Marijuana and health risks – assessing the science

Part 4. Marijuana and health risks – assessing the science

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

This is Part 4  of a series of six articles discussing marijuana’s use in medicine and health care. In this part, we discuss marijuana and health risks – even if there is evidence that marijuana had medical benefits, there must be a review of the risks of using it.

Only in junk medicine (see homeopathy or chiropractic, for example) is there a promise of great results with no risks. In real medicine, all benefits are balanced against the real risks of any medication or procedure.

The whole foundation of evidence (or science) based medicine is science – “it is the only set of methods for investigating and understanding the natural world.” Thus, the best factual evidence includes clinical research that describes not only the effectiveness, but also the risks, of a particular medical procedure.

In this article, I’ll look at marijuana and health risks – along with a skeptical analysis of those claims.

Risks of smoking marijuana


Notwithstanding the lack of quality and accurate labeling of current available “medical marijuana,” there are known risks to individuals who smoke marijuana. This is uniformly ignored by everyone, and there are even false claims that somehow smoking cannabis is safer than smoking other plants, like cigarettes. Part of the belief lies in the appeal to nature fallacy, which, in this case, implies that somehow marijuana is purer and healthier. The environmental damage from the poisons used to grow marijuana (which will, in fact, remain on the plant, and make up part of the what is inhaled) are legendary.

One of the reasons tobacco smoking is dangerous is that the epithelial cells in the lung, which make up a huge surface area of cells, are extraordinarily sensitive to environmental damages like air pollution and smoking. Though there is some evidence that marijuana smoking is less carcinogenic than tobacco, and in fact has components that have the opposite effects than tobacco smoke. But that shouldn’t be read that marijuana smoke has no carcinogenic properties, it is just less than cigarettes.

In a recent retrospective epidemiological study, the authors stated, “in conclusion, the results of the present study indicate that long-term cannabis use increases the risk of lung cancer in young adults.”

There is a “belief” that smoking pot is less problematic than smoking other types of plant material, such as tobacco, partially because some people smoke less pot that others who smoke cigarettes. This is a false assertion, because the reason why smoking is so tied to lung cancer is that the epithelial lining of the lung is susceptible to carcinogens; moreover, as the authors state, part of gaining effects of the pot is to inhale deeply and hold the smoke in the lungs for a greater period of time than in cigarettes (and certain cigars), it might actually increase the exposure of lung cells to the smoke and any associated carcinogens.

To be fair, the evidence is conflicting, but even in one large study that shows no conclusive evidence that there is an increased risk of lung cancer in non-cigarette smoking individuals, there appears to be increased risks for some types of cancer amongst marijuana smokers, including prostate cancer.

There’s also some recent evidence, published in a high impact factor journal, Human Reproduction, which found nearly double the risk of poor sperm morphology (with the possible result of infertility) after smoking marijuana (while cigarette smoking, type of underwear, and other myths about male fertility were shown to be irrelevant).

On the other hand, marijuana smoke deposits 4X as much tar in the lungs as do cigarettes. Although this may not be carcinogenic, tar can lead to the same non-cancer long-term damage to the lungs as do tobacco products–emphysema, bronchitis and lung infections.

In other words, if we’re looking at marijuana as a medical product, it’s risks are known and real. All real medications are evaluated on whether they provide a benefit and whether they have a risk. It is simply unscientific to make statements that marijuana treats this or that (even without high quality evidence) while completely ignoring whether it has some safety issues, including minor and major adverse events.



Quality of medical marijuana


There is an important issue regarding marijuana–for clinical use, the quality and strength of marijuana must be controlled. When I hear some of the strange comments about Big Pharma and cannabis, what many people fail to note is that Big Pharma invests a huge amount of research into controlling quality and dosage of the various products.

A recent study examined the quality of marijuana available for sale in three major US cities. They looked at the drug (that’s what it is) in three forms: baked, beverages and candy. Here’s what they found:

  • Edible cannabis products failed to meet basic label accuracy standards for pharmaceuticals. If a real pharmaceutical company provide products with labelling this bad, the FDA would probably have every executive arrested.
  • “Greater than 50% of products evaluated had significantly less cannabinoid content than labeled, with some products containing negligible amounts of THC.” If a real neurologist were to prescribe cannabis to treat symptoms from multiple sclerosis, the problem is that the physician has no idea if the patient can get a real dose. This point, this single point, is why medical claims about marijuana are so dangerous. This is why marijuana for medical uses should be strongly regulated. And that’s why Big Pharma will, some day, be the source of such products.
  • “Such products may not produce the desired medical benefit.”
  • “Other products contained significantly more THC than labeled, placing patients at risk of experiencing adverse effects.” Again, it’s not just that some product is worthless, some may have so much THC that it could be dangerous.

The researchers supported my own view of the medical marijuana business,  that is,:

[infobox icon=”quote-left”]Because medical cannabis is recommended for specific health conditions, regulation and quality assurance are needed.[/infobox]

If I were a medical researcher (oh wait….), and if marijuana had a real value medically (say it did cure breast cancer), smoking it would be the worst possible way to deliver the drug to the body. As I mentioned in the second part of this series, a real medical researcher would isolate the compound in marijuana that actually killed breast cancer cells, figure out a way to carry that molecule to the target site at the appropriate dose, and avoid harming the lungs. That’s how a real medical product is designed and tested.

See the next article in this series, Part 5. Marijuana and pregnancy – assessing the science.

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 six 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.

Key citations:

Michael Simpson

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