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Paul Armentano

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If Pot Prevented Cancer You Would Have Read About It, Right?

Posted: 08/17/09 07:31 PM ET

Two just-published studies assessing adults' risk of cancer have reported wildly divergent, and fairly extraordinary, outcomes. One study you may have read about. The other has been ignored entirely by the mainstream media. But no doubt the results of both will surprise you.

First, the study you may have heard of. Writing August 3 in the journal Cancer Epidemiology, investigators at McGill University in Montreal reported that moderate alcohol consumption -- defined as six drinks or fewer per week -- by adults is positively associated with an elevated risk of various cancers, including stomach cancer, rectal cancer, and bladder cancer.

And now for the study you haven't heard of. Writing in the August issue of the journal Cancer Prevention Research, investigators from Rhode Island's Brown University, along with researchers at Boston University, Louisiana State University, and the University of Minnesota reported that lifetime marijuana use is associated with a "significantly reduced risk" of head and neck squamous cell carcinoma.

Authors reported, "after adjusting for potential confounders (including smoking and alcohol drinking), 10 to 20 years of marijuana use was associated with a significantly reduced risk of head and neck squamous cell carcinoma (HNDCC)."

Perhaps even more notably, subjects who smoked marijuana and consumed alcohol and tobacco (two known high risk factors for head and neck cancers) also experienced a reduced risk of cancer, the study found.

"Our study suggests that moderate marijuana use is associated with reduced risk of HNSCC," investigators concluded. "This association was consistent across different measures of marijuana use (marijuana use status, duration, and frequency of use)....Further, we observed that marijuana use modified the interaction between alcohol and cigarette smoking, resulting in a decreased HNSCC risk among moderate smokers and light drinkers, and attenuated risk among the heaviest smokers and drinkers."

This isn't the first time that U.S. investigators have documented an inverse association between pot use and cancer. A separate 2006 population case-control study, funded by the U.S. National Institutes of Health and conducted by the University of California at Los Angeles, also reported that lifetime use of cannabis was not positively associated with cancers of the lung or aerodigestive tract, and further noted that certain moderate users of the drug experienced a reduced cancer risk compared to non-using controls.

Predictably, the federal government's goal when green-lighting the UCLA study was to conclusively establish just the opposite result, as explained recently by its lead researcher Dr. Donald Tashkin.

In an interview with the McClatchy newspaper chain in June, Dr. Tashkin admitted that he expected his study would find that pot was associated with "increased health effects." Instead, he summarized, "What we found instead was no association (between marijuana smoking and cancer) and even a suggestion of some protective effect."

Tashkin added, "[A]t this point, I'd be in favor of (marijuana) legalization. I wouldn't encourage anybody to smoke any substances. But I don't think it should be stigmatized as an illegal substance. Tobacco smoking causes far more harm. And in terms of an intoxicant, alcohol causes far more harm (than marijuana)."

Despite these findings, which to date inexplicably remain under-reported by the mainstream press, many so-called experts persist with claims that marijuana smoking is causally linked to cancer. In fact, in June the California Environmental Protection Agency with great fanfare added marijuana smoke to its list of chemicals that possess potential carcinogenic properties and/or are associated with reproductive toxicity. You know what other commonly indulged in substance also appears on this list? That would be alcohol. Of course that conclusion, much like the reports of marijuana's anti-cancer prowess, apparently went up in smoke.

Paul Armentano is the Deputy Director of the National Organization for the Reform of Marijuana Laws (NORML) and is the co-author of the new book Marijuana Is Safer: So Why Are We Driving People to Drink? (Chelsea Green Publishing).