Can Marijuana Cause Lung Cancer?

Marijuana use is legal, but that doesn’t mean it’s without health risks.

As more states legalize marijuana, many people might be wondering if that means it is safe to use. While smoking tobacco is a known and well-studied cause of lung cancer, linking marijuana to cancer is more complicated, says Brooks Udelsman, MD, a thoracic surgeon with USC Surgery, part of Keck Medicine of USC.

Ongoing research continues to explore the link between marijuana use and lung cancer risk. For instance, in a recent study by Keck Medicine led by Niels Kokot, MD, an otolaryngologist at the USC Caruso Department of Otolaryngology – Head and Neck Surgery, data suggested that patients who heavily smoked marijuana may have an increased risk of both small cell lung cancer and non-small cell lung cancer.

Another study led by Dr. Kokot showed that daily marijuana use can make someone 3.5 to 5 times more likely to develop head and neck cancers than people who do not use marijuana. Those head and neck cancer types include cancer of the mouth, pharynx, larynx, oropharynx (tongue and tonsils and back wall of the throat) and adjacent salivary glands. 

As research progresses, Dr. Udelsman says, one question that needs answering is how much marijuana use leads to increased cancer risk.

“What we don’t know right now is the dose relationship,” he says. “So, if someone smokes marijuana occasionally once a week, once a month or a few times a year, do they still have that same risk? My suspicion is that there is probably minimal risk. All we know right now is that people who smoke a lot of marijuana— to the point that they develop a dependency on it or require hospital care or evaluation for it — do appear to have a higher cancer risk.”

Researchers are also studying whether marijuana use is linked to other types of cancer such as bladder cancer or gastrointestinal cancer, Dr. Udelsman says.

“With tobacco, we do see an increased prevalence of bladder cancer. Whether that relationship is also the same for heavy marijuana smoking, we don’t know,” he says. “That’s why we’re trying to determine what the risks are so that people can know what risks they’re taking,” he says.

Is marijuana intake through non-smoking methods (consuming edibles, etc.) also associated with a risk of getting lung cancer?

“Probably not,” says Dr. Udelsman. “The risk is harder to track because there isn’t a lot of data on it yet, but as of now there does not seem to be a relationship between edibles and lung cancer. We don’t yet know if there is a link to other types of cancers, however.”

Which components in marijuana smoke can cause cancer?

Anything that causes prolonged or chronic inflammation can put your body at higher risk for cancer, Dr. Udelsman says. For instance, tobacco smoke contains more than 7000 chemicals, and about 70 of those are associated with cancer. Some of these chemicals are also present in marijuana smoke.

He adds that THC (tetrahydrocannabinol), the main psychoactive component in marijuana, is associated with the conversion of polycyclic aromatic hydrocarbons (PAHs). PAHs can induce inflammation and cause DNA damage. “Anytime inflammation and changes to DNA occur, you’re at risk for developing cancer,” he says.

Is secondhand marijuana smoke also linked to lung cancer?

There isn’t enough data yet to prove a link, but Dr. Udelsman says that secondhand marijuana smoke may create added risk because you’re inhaling some of the inflammatory particles that can lead to the development of cancer.

Are certain types of lung cancer more common with smoking marijuana?

There are two main types of lung cancer: small cell lung cancer and non-small cell lung cancer.

Small cell lung cancer is highly associated with smoking tobacco — and may also be associated with smoking marijuana, Dr. Udelsman says. “It’s almost unheard of to get small cell lung cancer without some type of inhalational injury,” he adds.

When it comes to non-small cell lung cancer, “We also see an increase in non-small cell lung cancer in smokers of both tobacco and marijuana, so both types are increased when compared to nonsmokers,” he adds.

Does vaping marijuana cause lung cancer?

Initially, some believed that vaping tobacco is safer than smoking tobacco. “But we are starting to see some very severe inflammatory diseases — not cancers, but benign diseases — from vaping,” Dr. Udelsman says. Since vaping has only existed for the last 15 years or so, and it usually takes many years to develop lung cancer, more time is needed to tell whether vaping tobacco causes lung cancer, he adds. The same goes for vaping marijuana.

“The data on vaping is very new, so we don’t know yet, but I’d worry about anything you’re breathing into your lungs because it infiltrates the cells and air sacs in your lungs, which can cause damage and put you at a higher risk for cancer,” Dr. Udelsman says.

How much marijuana smoking is dangerous?

A lot of people smoke marijuana recreationally, and Dr. Udelsman does not think that this will cause an epidemic of lung cancer.

“I worry less about occasional use and the slight inflammation that it might cause for a temporary period. Your body probably recovers from that very quickly, with very little damage,” he says. “I’m more worried about chronic, heavy exposure: people who are using marijuana every day, multiple times a day. That’s where I think you can start to build up injury. Those are the people data today shows are at risk for developing cancer, similar to tobacco.”

If you do smoke marijuana heavily, talk with your doctor so they can stratify your risk and help determine if you may benefit from further evaluation.

Topics