Pop Quiz Hotshot

Q: The results of the largest case-controlled study ever conducted to investigate the respiratory effects of marijuana smoking and cigarette smoking were released in 2006. Which of the following conclusions did it reach?

a) Marijuana use significantly increased the likelihood of developing lung cancer.

b) Marijuana smoking was not associated with an increased risk of lung cancer.

c) Marijuana smokers and cigarette smokers were equally likely to develop lung cancer.

d) Marijuana-only smokers were more likely than cigarette-only smokers to develop lung cancer.

The answer, perhaps to your surprise, is b.

Not only was marijuana smoking not associated with an increased risk of lung cancer, but it was not found to be associated with lung-related cancers at all, even among subjects who had smoked up to 22,000 joints in their lifetimes. The study’s lead researcher, Dr. Donald Tashkin at the University of California at Los Angeles, offered, "We hypothesized that there would be a positive association between marijuana use and lung cancer … What we found instead was no association at all, and even a suggestion of some protective effect." What the latter part of that quote means is that people who smoked marijuana actually had *lower* incidences of cancer compared to non-users of the drug.

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