Does Smoking Marijuana Cause Lung Cancer? Top Experts Tell SurvivorNet a Public Health Crisis is Coming

SurvivorNet’s extensive review of the medical literature finds no high-quality scientific research establishing a direct link between smoking, or vaping, marijuana and an increased risk of developing lung cancer. This is largely due to the fact that smoking pot was illegal for so long and therefore not easy to study in a long term way. The lack of rigorous scientific data has been quickly embraced by the booming cannabis industry, which is starting to be called “big marijuana.”

Experts Call for a Major National Study 

"Given the expanding legalization of marijuana, and the anticipated wave of increased use, there is clearly a need to study the cancer risks of marijuana with the same rigor that has been devoted to tobacco smoke,” says Dr. Joseph Friedberg, Head of the Division of Thoracic Surgery at the University of Maryland School of Medicine. “Both types of smoke contain some of the same carcinogens, so the widely held belief that tobacco smoke causes cancer and marijuana smoke does not is inherently flawed.”

“There is a lobby out there that is trying to say that marijuana’s better than drinking, that it’s safer, that it doesn’t cause cancer, and that you should do that. And they’re both bad,” says Dr. Flores. There is no real good population-based study that looks at marijuana smoking, and that has had enough time elapsed to show its association with lung cancer,”

“Just as cigarettes come with health risk warnings, the risks of marijuana smoke need to be defined for users to allow them to make an informed decision about smoking pot,” adds Dr. Friedberg.

The scientific evidence

Dr. Donald Tashkin, a pulmonologist from UCLA , has studied marijuana for 30 years. He has published research, written review articles, and given talks to doctors on the topic. He says there is a lot of evidence to suggest marijuana may cause cancer. This includes:

• Known carcinogens in the smoke of marijuana
• Genes implicated in the development of lung cancer are over expressed in the lungs of pot smokers
• Tissue in the lungs of marijuana smokers compared to non-smokers have a higher proportion  precancerous changes

But Tashkin says when you look at human studies the evidence is not there. Tashkin says of the six well done human studies five showed no association between marijuana and lung cancer and the sixth actually shows a benefit. “The weight of evidence thus far available would argue against a significant association,”Tashkin says. And he says when he gives talks to doctors they “scratch their head when they look at the evidence because the expectation is that there should be a positive association between marijuana smoking and lung cancer.”

The question is “why’. There may be a number of reasons but Tashkin believes one important possible explanation is “the difference between marijuana smoke and tobacco smoke is that marijuana smoke also contains THC.” He says the chemical THC has been shown in studies in a variety of different cancers to have an anti-tumor effect. So it is possible marijuana does not cause lung cancer because of the THC. However Tashkin does believe it would be worthwhile to do a study to get a more definitive answer. And the growing availability of marijuana would argue for such a study being done now.

Recreational vs Medical Marijuana 

Medical marijuana is now legal in thirty-three states. Cannabis ingested in any number of ways, including smoking, is fundamentally a game-changer for people with pain or nausea from chemotherapy, or excruciating side effects from cancer treatment such as shingles.

Pot can really help during cancer treatment, but be cautious.

Comparatively less attention has been paid to the the potential health impact of smoking marijuana recreationally. It is now legal to smoke marijuana for recreational purposes in ten states, and many more American cities have essentially decriminalized its use. 

SurvivorNet was struck by the number of highly trained surgeons describing in vivid detail the biological ravages of repeated recreational pot smoking. "I've seen multiple, multiple cases of it. I see it every day. I'll give you one for example. A patient never smoked before. Has been smoking weed since they were about 15, about a joint a day. And now they're 30, 35, and they have a very aggressive lung cancer. They have these changes in their lungs that are emphysematous that you get from smoking," Dr. Flores says. "Then when you look at their skin, you see the cancer there, just like in a smoker. You see a solid nodule there that's eating away at the normal one. And patients say, Doc, I didn't know I could get that from marijuana. They always said marijuana doesn't cause lung cancer. And that really saddens me."

Isn’t Vaping Less Dangerous?

Today, many people are vaping, not smoking, marijuana and wonder if vaping presents less of a risk for developing lung disease than smoking.

For the uninitiated, vaping involves inhaling marijuana vapor through the mouth from a tiny battery-operated electronic device that looks like a cigarette that heats up and vaporizes the marijuana.

In this case, vaping is so new that no definitive scientific studies exist, so researchers and the companies that sell the products really don’t know the danger with a level of certainty that’s acceptable for established science. However, like smoking, vaping is essentially a delivery mechanism that creates an aerosol.

“When you burn a product and you inhale it, that’s carcinogenic. And with vaping, the idea is to create an aerosol which you can inhale that is not burnt product. However, whenever you have carcinogens in an aerosol, they will cause cancer, ” agues Dr. Flores.

Aerosols are a quick way for the body to develop a reaction to a substance, (i.e. to get high). Basically products are smoked because it’s a quick way to get them from the mouth, to the lung and into the bloodstream so that people feel the effect very quickly.  That’s why aerosols, (i.e smoking or vaping), work so well.

“What an aerosol also does is it takes the products that cause harm to your body, whether it’s cancer, whether it’s COPD, whether it’s coronary artery disease and it gets it into your body quickly and at a high concentration where it can cause more damage. So aerosols are bad,” according to Dr. Flores.

But again, with vaping and marijuana, it is important to point out that researchers really don’t know how to quantify the effects.

“What needs to happen to really study the effect of vaping is you need animal studies. You want to take animals studies where you give them high concentrations of aerosol and see what happens with regard to cancer, lung disease, and coronary artery disease. But none of those studies are being done. Essentially, what happens nowadays, when you have a product that we know has the potential to cause harm, cancer, et cetera, there’s an assault on that science. The business behind the product will make sure that they kick the can down the road to postpone any discovery of harm that can result from that substance. Billions of dollars are dependent on casting doubt on the fact that their product has carcinogens that are causing harm to people,” says Flores.

What Do Marijuana Smokers Believe?

SurvivorNet went recently to MJBizCon, the largest cannabis conference in the country. This is one of the few places that people want to speak on the record about their recreational pot use.  "I smoke pot every day and haven't been to the doctor in ten years," said a man who appeared to be in his forties. “Show me the proof smoking pot causes cancer,” said another woman. “If anything, I’ve known more people where smoking cannabis has fixed their cancer.”

“Those who do not learn history are doomed to repeat it seems applicable here as we have an opportunity to avoid a potential marijuana-related public health crisis similar to what we are still dealing with from cigarettes being introduced to the public without any health risk warnings," says University of  Maryland’s Dr. Friedberg, who has spent decades as a noted surgeon managing care for people with lung cancer.

“Smoke ‘Em If You Got ‘Em” 

The public health crisis caused by tobacco during the last century had a lot to do with marketing and the larger social perception of smoking, which is likely to be at least partially the case with marijuana.

As early as World War I, tobacco marketing was focused on military men.

“Smoke this when you’re stressed, when you’re sitting there on the front line, when you’re sitting around in your barracks and you have nothing more to do. And they give them the cigarettes? Why? Because they wanted to get them hooked on it. And that’s where ‘smoke ’em if you got ’em’ came from.  It’s because when they were on their long hikes, they were given breaks. And they said, “All right, you’ve got a ten-minute break. You can smoke.” If you didn’t have a cigarette to smoke, instead, you did ten push-ups.

Proving a Link to Cancer Takes a Long Time

Perhaps the first large, seminal scientific study of cigarette smoking was done in Britain and involved 40,000 doctors. It started in 1951 and took three years to establish a causal link between cigarette smoking and lung cancer. The study, and similar subsequent work, went on for decades to confirm the long-term impact of smoking and smoking cessation.

“For something to give you cancer, it doesn’t just happen in two to five years. It takes 20 years, 30 years, 40 years. You need large numbers of patients and a long period of time to prove it and those studies are expensive, they take time and they’re labor intensive, says Dr. Flores of Mt Sinai.

“Just because we don’t have the numbers yet, because we haven’t been recording this data, doesn’t mean that marijuana is safe,” argues Flores. what you’re going to see going down the line is the reincarnation of the whole tobacco disaster. I see it now already. Big business and the money influence are taking precedence over health issues.”

In a recent New Yorker magazine article, the writer Malcolm Gladwell argued that, “For the moment, cannabis probably belongs in the category of substances that society permits but simultaneously discourages” or limits cigarettes, alcohol, prescription drugs.”

The urgent question now is how quickly the country is going to work to really understand the health effects of marijuana, what will be done with that knowledge, and will it be too late?”

 

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