WEDNESDAY, April 23, 2014 -- Marijuana use might contribute to heart and artery disease among young and middle-aged adults, particularly those already at risk for cardiovascular problems, a small French study reports.

By reviewing reported cases of marijuana abuse in France between 2006 and 2010, researchers identified 35 users who suffered heart disease -- including 20 heart attacks and nine deaths.

The percentage of heart disease cases among reported marijuana abusers more than tripled during those five years, rising from 1.1 percent of cases to 3.6 percent, the investigators reported.

In nearly half the cases, the afflicted pot users already had risk factors for heart disease such as high blood pressure or high cholesterol, the study authors said.

"This unexpected finding deserves to be further analyzed, especially given that the medicinal use of marijuana has become more prevalent and some governments are legalizing its use," said Emilie Jouanjus, lead author of the study and a medical faculty member at the University Hospital of Toulouse in France.

But marijuana advocates argue that the findings appear weak at best, given that the percentage of pot users with heart problems is so small.

"If those are the chances of having cardiac complications as a French cannabis user, my first thought is that using cannabis protects people from cardiac problems," said Mitch Earleywine, a professor of psychology at the State University of New York at Albany and board chair of NORML, a marijuana advocacy group.

"We need a comparison group of people who don't use cannabis to know their rate of cardiac problems, but, as the authors point out, we simply don't have those data," Earleywine added.

The study authors reviewed cases of marijuana abuse reported to the French Addictovigilance Network. Doctors are legally required to report drug abuse cases to the network if they believe the drug use could lead to serious health problems.

Previous studies have linked marijuana use to an increased risk of heart attacks and cardiovascular disease, the authors said in background information.

For this study, published April 23 in the Journal of the American Heart Association, researchers identified 1,979 reports of marijuana abuse during the five-year period. Of those cases, 35 involved cardiovascular complications.