Young marijuana users may face increased risk of heart attacks and other serious cardiovascular problems, according to a new study.
Records from the French Addictovigilance Network, a system of national centres in France that collects information about drug abuse, revealed a clear link between cardiovascular complications and cannabis use.
Researchers found 35 reports of patients who experienced cardiovascular problems, including heart attacks and strokes, after using marijuana between 2006 and 2010. The average age of the patients was 34 and the overwhelming majority (85%) were men. In nine cases the patient died.
Around 20% of patients had a known history of cardiovascular problems, although others may have had separate, unknown health issues.
While the study does not certify that marijuana use definitively causes such health problems, scientists have suggested more research is needed.
Emilie Jouanjus, lead author of the study at the Université Toulouse III – Paul Sabatier, said the number of people seriously affected by cannabis use is actually under-reported, and told CNN: "Currently people think [cannabis is] harmless.
"What I think is very important from my work is that we see cannabis use may lead to very serious complications on the cardiovascular system."
"I'm not saying that any user of cannabis would suffer from any of these complications. But we do not have enough information to say that cannabis use is safe."
In a separate interview with Medical News Today, Joanjus described the study as providing "compelling evidence" of the link between marijuana and cardiovascular problems among young people, adding: "It is therefore important that doctors, including cardiologists, be aware of this, and consider marijuana use as one of the potential causes in patients with cardiovascular disorders."
Medical marijuana is legal in 21 US states and the District of Columbia. This week, a separate study in the Journal of Adolescent Health stated legalisation of the drug does not increase use among adolescents.
Esther Choo, a doctor at Rhode Island Hospital, said: "In this study, we examined 20 years worth of data, comparing trends in self-reported adolescent marijuana use between states with medical marijuana laws and neighboring states without the laws, and found no increase in marijuana use that could be attributed to the law."
Yet Dr Shereif Rezkalla, a cardiologist at the Marshfield Clinic in Wisconsin, said more research needed to be done to protect communities from the dangers of widespread marijuana use "in the absence of safety studies". She told the LA Times: "It is the responsibility of the medical community to determine the safety of the drug before it is widely legalised for recreational use."
The study was published in the Journal of the American Heart Association.