Study: Secondhand Cannabis Smoke More Harmful Than Cigarettes

Cigarette smoke may not be as harmful as secondhand cannabis smoke, according to a new study by the American Heart Association.

The study -- newly published in the Journal of the American Heart Association -- found that rats' arteries carried blood less efficiently for an hour and a half after having inhaled one minute's-worth of cannabis smoke; when rats inhaled cigarette smoke for the same period of time, their arteries carried less blood for only 30 minutes.

"While the effect is temporary for both cigarette and marijuana smoke, these temporary problems can turn into long-term problems if exposures occur often enough and may increase the chances of developing hardened and clogged arteries," said a senior author of the study, Matthew Springer, Ph.D., who is also a professor of medicine at the University of California, San Francisco's Division of Cardiology.

According to Springer, the blood vessels of rats and humans are similar enough so that a study on one could likely apply to the other.

"Arteries of rats and humans are similar in how they respond to secondhand tobacco smoke, so the response of rat arteries to secondhand marijuana smoke is likely to reflect how human arteries might respond," he said.

Springer went on to say that while many states continue to liberalize their laws regarding the medicinal and recreational use of cannabis, it is nonetheless important for prospective patients and consumers to understand the potential risks involved with the use of cannabis.

"There is widespread belief that, unlike tobacco smoke, marijuana smoke is benign," he stated. "We in public health have been telling the public to avoid secondhand tobacco smoke for years. But we don't tell them to avoid secondhand marijuana smoke, because until now we haven't had evidence that it can be harmful."

John Winston is a New York City-based journalist and a media advisor for