Why Was a Pot-Doesn't-Cause-Cancer Study Ignored?

By Tony O'Neill 10/24/12

Media reactions to research on marijuana and lung cancer show prejudice.

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If a major study suggested that smoking marijuana not only doesn't cause lung cancer but may even reduce its incidence among those who smoke tobacco, you'd assume it would cause something of a media sensation. Well, it didn’t. A fascinating AlterNet article highlights how the mainstream media completely ignored the startling 2005 findings by Donald Tashkin, professor of pulmonology at UCLA’s David Geffen School of Medicine.

Tashkin, who will discuss his past findings and current research at a University of California San Francisco doctors' course tomorrow, doesn’t fit the lazy stereotype of a marijuana advocate. His pioneering work in the 1970s first identified the toxic compounds in pot smoke, and his lab was the first to report that one of tobacco’s most carcinogenic components—benzpyrene—is prevalent in marijuana smoke too. Tashkin’s data, showing that marijuana smokers were more likely to cough, wheeze and produce sputum than non-users was widely propagated to scare people away from smoking pot. His work made him a darling of the government's National Institute of Drug Abuse, which seized on his findings; NIDA then gave Tashkin a large grant to conduct a widespread, population-based study to prove beyond doubt that long-term marijuana use increases your risk of lung cancer.

But the annoying thing about science—as Richard Nixon learned when he ordered an investigation of marijuana risks back in 1972—is that sometimes it tells you things you don’t want to hear. Tashkin’s findings were the opposite of what NIDA expected. His work indicated that increased pot use alone, despite causing some damage to respiratory cells, doesn't increase the risk of lung and pharyngeal cancer. Tobacco smokers, in contrast, were found to be at a greater risk the more they smoked. Amazingly, people in Tashkin's control group, who smoked both tobacco and marijuana, were found to be at slightly lower risk than their tobacco-only counterparts.

The startling implication was that something in marijuana stops damaged cells from becoming malignant: Tashkin theorized an anti-proliferative effect of THC, which has been previously observed in cell-culture systems and animal models of brain, breast, prostate, and lung cancer. THC has been shown to promote known apoptosis (damaged cells die instead of reproducing) and to counter angiogenesis (the process of blood-vessel formation, which is a requirement of tumor growth). Tashkin thought other antioxidants in cannabis may also help counter malignancy.

It’s no surprise that a pro-prohibition institution like NIDA chose not to publicize this report. But why did mainstream media look the other way when Tashkin’s findings emerged in 2005? They did the same in 2009, when Tashkin went public to counter a New Zealand study, claiming that marijuana increases the risk of lung cancer, which he called “statistical sleight of hand.” A very small sample size didn't stop it receiving far wider publicity at the time than Taskin's study. It seems that marijuana scare stories simply sell.

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Tony O'Neill, a regular contributor to The Fix, is the author of several novels, including Digging the VeinDown and Out on Murder Mile and Sick City. He also co-authored the New York Times bestseller Hero of the Underground (with Jason Peter) and the Los Angeles Times bestseller Neon Angel (with Cherie Currie). He lives in New York with his wife and daughter. You can follow Tony on Twitter.