Marijuana Secondhand Smoke Seen as Damaging to Arteries as Tobacco Smoke

Marlene Busko

December 03, 2014

CHICAGO, IL — Breathing secondhand marijuana smoke may be just as damaging to the heart and blood vessels as inhaling secondhand cigarette smoke, a small study in rats suggests[1].

When the rats were exposed to marijuana smoke in a laboratory for half an hour, arterial flow-mediated dilation dropped by 50% to 70%, senior author Dr Matthew L Springer (University of California, San Francisco) said, presenting these findings at the American Heart Association (AHA) 2014 Scientific Sessions.

Impairment in the ability of arteries to dilate was similar when the rats were exposed to smoke from marijuana with vs without tetrahydrocannabinol (THC), the primary psychoactive ingredient. Thus, "this is an effect of marijuana as a smoke source, not as a drug," Springer stressed.

The reduced blood-vessel function mimicked findings in the researchers' recently published similar study of rats exposed to secondhand tobacco smoke[2].

Thus, the current study shows that "smoke is smoke," Springer said. When clinicians ask patients about smoking or exposure to secondhand smoke, they should also ask about "smoke from cigarettes, cigars, hookah, and marijuana, as well as wood fires and other sources of smoke from burning, dried-plant material," he told heartwire .

Asked to comment, Dr Nancy A Rigotti (Massachusetts General Hospital, Boston), who was not involved with the study, cautioned that "finding this in rats doesn't prove that it will happen in people, but the rat model has been associated with this effect on people for tobacco smoke, so it is likely to be the case for marijuana."

The important message is that "inhaling smoke is not good for your heart, no matter what is burned to make the smoke, [and] patients with coronary heart disease should avoid exposure to smoke of any type," she said.

Springer and coauthors and Rigotti reported they have no relevant financial relationships.

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