Marijuana may up heart attack, stroke risk: study

The researchers said the active ingredient in marijuana, known as THC, seems to overstimulate marijuana receptors in the liver, leading to overproduction of the protein.

RAISING FUTURE RISK

Cadet said higher levels of the protein in marijuana users could raise future risk for cardiac abnormalities, blood flow problems, heart attack and stroke.

People with major medical or psychiatric illness, alcohol dependency and other drug use such as cocaine or heroin were excluded from the study.

A U.S. group supporting legal sales and regulation of marijuana disputed the findings. Marijuana Policy Project spokesman Bruce Mirken said, for example, the study involved people who were extremely heavy users.

"I think the low end was 78 joints a week. That's 10 or 11 joints a day," Mirken said in a telephone interview.

"We're talking about people who are stoned all the time. We're talking about the marijuana equivalent of the guy in the alley clutching a bottle of cheap wine. If you do anything to that level of excess, it might well have some untoward effects, whether it's marijuana or wine or broccoli," Mirken added.

Cadet's team said the findings suggest long-term harm from marijuana beyond issues such as impaired learning, poor memory retention and retrieval and perceptual abnormalities.

But Mirken said: "Even if you take this finding at face value, it's not at all clear that it has any relevance to the real world because there is still no data showing higher rates of mortality among marijuana smokers. If this was a significant cause of cardiovascular disease, where are the bodies?"

(Editing by Maggie Fox and Doina Chiacu)