Heavy marijuana use may be related to an increase in a blood protein linked to heart disease, although researchers did not look at whether study subjects actually had heart problems, Reuters reported May 13.

Researchers at the National Institute on Drug Abuse found that levels of apolipoprotein C-III, which is involved in metabolism of triglycerides in the blood, were higher among 18 long-term heavy marijuana users than among a control group of 24 non marijuana users. High levels of triglycerides can cause hardening of the arteries, raising the risk of stroke or heart attack.

"Chronic marijuana use is not only causing people to get high, it's actually causing long-term adverse effects in patients who use too much of the drug," said lead researcher Jean Lud Cadet. "Chronic marijuana abuse is not so benign."

The study subjects smoked between 78 and 350 marijuana cigarettes per week. "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," said Bruce Mirken, a spokesperson for the Marijuana Policy Project. "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, "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?"

The study appeared in the May 13, 2008 issue of the journal Molecular Psychiatry.