MONTREAL — New research based on U.S. hospital statistics suggests that recreational cannabis users are increasingly at risk of stroke.
In findings presented Friday at the World Stroke Congress in Montreal, scientists from Avalon University in Curacao used a database covering 1,000 hospitals to analyze trends in stroke prevalence and stroke-related hospital stays among recreational marijuana consumers.
Looking at more than 2.3 million hospitalizations of adult cannabis users from 2010 through 2014, researchers found a steady increase in the number of strokes suffered.
Of the total, 32,231 — or 1.4 per cent — had a stroke, including 19,452 with acute ischemic stroke, which occurs when arteries to the brain narrow or are blocked.
Over the five-year period, researchers found a 15 per cent rise in all types of stroke and a 29 per cent rise in acute ischemic stroke among cannabis users. The results held across all age groups.
"The trend is increasing," Dr. Krupa Patel, the lead researcher, said in an interview.
"We also looked at the general population, and we didn't identify any trends, meaning that the rates of stroke in the general population was stable."
While the research suggests there is a potential link to stroke because of the effects of cannabis on the brain's blood vessels, additional study is needed to establish a causal link.
"More prospective studies need to be done to understand where the 15 per cent and the 29 per cent (increases) are coming from," Patel said.
She said previous studies have focused on tobacco and cocaine as compounding the risk of strokes.
Patel said further research is needed on the interaction between cannabis and illicit drugs. It is also unclear whether stroke risk could be related to the frequency and duration of cannabis use and whether there is a genetic or racial susceptibility.
In the meantime, the study recommends abstinence from cannabis for pregnant women, due to fetal risk, and for adolescents, whose brain development is not complete. It also says anyone with pre-existing conditions or who is taking medications or other drugs should consult a physician before consuming recreational marijuana.
Francine Forget Marin, director of health promotion and research for the Heart and Stroke Foundation's Quebec branch, said it is a coincidence that the study has come out the same week Canada legalized recreational cannabis use.
"It's one study, and we need more research to establish if there's a link between cannabis users and heart attack and stroke," she said.
Sidhartha Banerjee, The Canadian Press