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.
Most of the study patients were male, with an average age of 34. Of 22 heart-related cases, there were 20 heart attacks. Another 10 involved disease related to arteries in the limbs, and three were related to the brain's arteries.
In 16 of the 35 cases (46 percent), the patients either had personal risk factors for heart disease or a family history of heart problems, according to the report.
The amount of cardiovascular disease among marijuana users is most likely underreported, given that the drug is illegal, said Dr. Suzanne Steinbaum, a preventive cardiologist at Lenox Hill Hospital in New York City.
The study authors said it's estimated that 1.2 million people in France regularly use marijuana.
"Because of marijuana being illegal, it is most likely these statistics are less reported and that it underestimates the amount of younger people whose behavior has affected their hearts," Steinbaum said. "In younger people who have risks for cardiovascular disease, whether it be their own risk factors or their family history, there needs to be an understanding that using marijuana might be an unsafe choice for them and can lead to cardiovascular events, and potentially death."
But Earleywine said the study's reliance on an incomplete database renders its observations meaningless.
"In short, this study tells us a lot about what kinds of cardiac complications appeared in people who were reported to the French government for cannabis-related problems, but tells us little about the link between cannabis use and cardiovascular disease," he said.
Dr. Martha Daviglus, adjunct professor of preventive medicine at the Northwestern University Feinberg School of Medicine in Chicago, acknowledged that the study has flaws. However, she added that such research is needed given that medicinal and recreational marijuana use is becoming more widely accepted.
"We need to gain more evidence, as we did with alcohol or tobacco smoking, so people understand the risks of using these substances," Daviglus said.
For more about marijuana, visit the U.S. National Library of Medicine.