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Does marijuana cause lung cancer? Doctors call for more research

Posted at 1:29 PM, Apr 13, 2019
and last updated 2019-04-13 14:34:02-04

(NBC) – Early in his career operating on lung cancer patients, Dr. Raja Flores knew most were cigarette smokers. But through the years, Flores, a thoracic surgeon at Mount Sinai Medical Center in New York, noticed a startling pattern: Some of his patients had never smoked a tobacco cigarette. They smoked a different drug: marijuana. And they had developed a much more aggressive form of lung cancer.

Initially, Flores didn’t consider there could be a connection between marijuana and lung cancer. The research linking pot smoking with cancer was scant and largely inconclusive. But as the numbers grew, Flores wondered if he was seeing some kind of grim new trend.

“I said to myself, ‘wait a minute, here’s another person in his 40s who never touched a cigarette and the cancer is all over the place,” Flores told NBC News. “It’s so bad I can’t even operate.’”

Flores acknowledges there isn’t scientific proof that smoking cannabis causes lung cancer. But he worries that the combination of widespread legalization and marketing of marijuana’s potential health benefits are contributing to the belief that cannabis is an entirely benign drug. In fact, a nationally representative survey of U.S. adults published last summer found that nearly a third thought that smoking or vaping weed could protect a person’s health. And that misperception could lead to the development of cancers from marijuana use, but undetected by the drug’s proponents, Flores believes.

Many Americans held a similar view of tobacco before evidence accumulated showing that cigarette smoking could cause lung cancer, said pulmonologist Dr. Panagis Galiatsatos, a critical care instructor at Johns Hopkins School of Medicine and director of the tobacco treatment clinic at Johns Hopkins Medicine.

Until the number of cigarette-related lung cancer cases accumulated to a level that no one could ignore, there were even respected scientists who dismissed warnings about the potential dangers associated with smoking tobacco, Galiatsatos said.


Most research says no, but that doesn’t mean that smoking joints long-term comes without consequences.

2016 review monitoring health concerns related to marijuana usefound strong evidence for an association between daily or near-daily marijuana use and chronic bronchitis, an inflammation of the airways of the lung that causes cough, wheezing and shortness of breath.

“There are respiratory effects to using smoked marijuana for long periods of time,” said Dr. Russell Bowler, director of the COPD clinic at National Jewish Health in Denver. He’s a member of the the Retail Marijuana Public Health Advisory Committee for the Colorado Department of Public Health and Environment, which commissioned the study.