Pulmonary Risk for Marijuana-Only Smokers Far from Clear


Earlier this week there was a smattering of press attention to a study published in the Canadian Medical Association Journal,
dealing with a deadly lung condition known as chronic obstructive
pulmonary disease, or COPD. “Marijuana plus cigarettes boosts lung
disease risk,” is how Reuters headlined the story.

The study suggested that the combination of marijuana and cigarettes
may be worse than cigarettes alone. It did not find that marijuana by
itself increased the risk of COPD, but Reuters went out of its way to
say that the study had not proved there was no such increased risk.

As usual, the reality was a bit more complicated than the press reports.

While the study did find a suggestion of increased risk for those
who smoked both marijuana and cigarettes, the risk for marijuana-only
smokers was far from clear. Indeed, by some measures the COPD risk was
actually less in the marijuana-only smokers than nonsmokers, but
numbers were small enough that the differences were not statistically

What most news accounts, including Reuters, failed to mention, is
that there is a great deal of other data about marijuana and COPD, data
that was summarized in an accompanying review by Dr. Donald Tashkin of UCLA, one of the world’s leading experts on the effects of marijuana on the lungs. Tashkin wrote, “Given the consistently reported absence of an association between use of marijuana and abnormal diffusing capacity or signs of macroscopic emphysema, we can be close to concluding that smoking marijuana by itself does not lead to COPD [emphasis added].”

Bottom line: Cigarettes are really bad for your lungs.
Combining cigarettes and marijuana might be even worse. Marijuana alone
is clearly far less harmful — but it’s still a good idea to vaporize
rather than smoke.


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