Secondhand marijuana smoke may damage blood vessels as much as tobacco smoke

(Press-News.org) Breathing secondhand marijuana smoke could damage your heart and blood vessels as much as secondhand cigarette smoke, according to preliminary research presented at the American Heart Association's Scientific Sessions 2014.

In the study, blood vessel function in lab rats dropped 70 percent after 30 minutes of exposure to secondhand marijuana smoke. Even when the marijuana contained no tetrahydrocannabinol (THC) -- a compound in marijuana that produces intoxication -- blood vessel function was still impaired.

Reduced blood vessel function may raise the chances of developing atherosclerosis and could lead to a heart attack. Atherosclerosis is the disease process that causes plaque build-up in the arteries which narrows them and restricts blood flow.

"Most people know secondhand cigarette smoke is bad for you, but many don't realize that secondhand marijuana smoke may also be harmful," said Matthew Springer, Ph.D., senior author of the study and cardiovascular researcher and associate professor of Medicine at the University of California, San Francisco's Cardiology Division.

Marijuana and tobacco smoke are chemically and physically alike, aside from their active ingredients.

The drop in blood vessel function from THC-free marijuana suggests that the compound isn't responsible for the effect. Similarly, this study confirms that nicotine is not required for smoke to interfere with blood vessel function.

In the study, researchers used a modified cigarette smoking machine to expose rats to marijuana smoke. A high-resolution ultrasound machine measured how well the main leg artery functioned. Researchers recorded blood vessel dilation before smoke exposure and 10 minutes and 40 minutes after smoke exposure.

They also conducted separate tests with THC-free marijuana and plain air. There was no difference in blood vessel function when the rats were exposed to plain air.

In previous tobacco studies, blood vessel function tended to go back to normal within 30 minutes of exposure. However, in the marijuana study, blood vessel function didn't return to normal when measured 40 minutes after exposure.

Now that marijuana is becoming increasingly legalized in the United States, its effect on others is a growing public health concern, Springer said.

"If you're hanging out in a room where people are smoking a lot of marijuana, you may be harming your blood vessels," he said. "There's no reason to think marijuana smoke is better than tobacco smoke. Avoid them both."

Secondhand tobacco smoke causes about 34,000 premature deaths from heart disease each year in the United States among nonsmokers according to the U.S. Surgeon General's 2014 report on the consequences of smoking.

More research is needed to determine if secondhand marijuana smoke has other similar effects to secondhand cigarette smoke in humans.

INFORMATION: Co-authors are Xiaoyin Wang, M.D.; Ronak Derakhshandeh, M.S.; Shilpa Narayan, B.S.; Emmy Luu, B.S.; Stephenie Le, B.A.; Olivia Danforth, B.S.; Hilda Rodriguez; Richard Sievers, B.S.; Suzaynn Schick, Ph.D.; and Stanton Glantz, Ph.D. Author disclosures are on the manuscript.

The National Institute on Drug Abuse and the Elfenworks Foundation funded the study.

Additional Resources: Downloadable video/audio interviews, B-roll, animation and images related to this news release are on the right column of the release link Video clips with researchers/authors of the studies will be added to the release link after embargo. AHA blog: States move forward with marijuana legalization despite lack of research Smoking: Do you really know the risks? For more news from the AHA's Scientific Sessions 2014, follow us on Twitter @HeartNews #AHA14.

Statements and conclusions of study authors that are presented at American Heart Association scientific meetings are solely those of the study authors and do not necessarily reflect association policy or position. The association makes no representation or warranty as to their accuracy or reliability. The association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific association programs and events. The association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and device corporations are available at http://www.heart.org/corporatefunding.

Note: Actual presentation is 9:30 a.m. CT / 10:30 a.m. ET, Monday, Nov. 17, 2014 (South Hall A2, Core 7).

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