Intracranial stenosis seen three times as frequently in cannabis users versus non-users
Regular cannabis users who suffer ischemic strokes before the age of 50 tend to be significantly younger and more likely to have strokes caused by intracranial arterial stenosis compared to patients who do not smoke pot, researchers reported.
In the first study to compare stroke characteristics and prognosis in younger patients who do and do not smoke marijuana, researchers recorded consecutive hospital admissions for ischemic stroke among patients under the age of 45 over a 9-year period at a single teaching hospital in Strasbourg, France.
Among the 334 hospital patients in this age group admitted to the hospital during the study period, 58 (17.4%) reported that they were regular cannabis users.
“Cannabis users were significantly younger, more frequently men, and consumed tobacco and alcohol more frequently than non-cannabis users,” researcher Valerie Wolff, MD, PhD, of the University Hospital Strasbourg, and colleagues wrote in the Journal of the American College of Cardiology, published online Oct. 26.
The study did not address the controversial question of whether regular marijuana use is causally linked to higher stroke risk in younger adults. But the finding that cannabis users had more strokes caused by intracranial arterial stenosis is consistent with theories of a possible mechanism for this association, Wolff told MedPage Today in an email exchange.
“Cannabis is a known precipitant factor of reversible cerebral vasoconstriction syndrome (RCVS),” Wolff wrote. “We showed in a series of 159 ischemic stroke in the young that the mechanism may be RCVS in 13% of cases. Our results in the new study confirm that intracranial arterial stenosis (one criteria of RCVS) is a frequent cause of stroke.”
Oklahoma City internist Mary Ann Bauman, MD, who chairs the American Stroke Association advisory committee, said that while randomized studies are needed to prove a causal link between marijuana use and stroke, the findings by Wolff and colleagues do lend support to the idea that reversible arterial vessel constriction associated with cannabis use may increase stroke risk.
“This study also illustrates how much we really don’t know,” Bauman told MedPage Today. “We don’t know what will happen as marijuana becomes legal in more places and becomes more mainstream. My very great worry is for young people who think there are no health risks to marijuana use at all.”
In the newly published study, Wolff and colleagues examined illicit drug use (cannabis, cocaine, and amphetamines) for all ischemic stroke admissions among patients younger than age 45 from 2005 to 2014. Neurological symptoms were recorded at admission and stroke prognosis was evaluated 3 months after the event using the modified Rankin scale.
Intracranial arterial stenosis was found to be the main etiology of stroke in cannabis users, occurring in 45% of these patients compared to just 14.5% of noncannabis users. Among non-users cardioembolism was the most frequent cause of stroke, occurring in 29.3% of patients compared to 14% of cannabis users.
At admission, cannabis users and non-users displayed similar symptoms of 1-sided motor deficit, but cannabis users had more visual disorders and less aphasia compared to non-users.
At 3-month follow-up, functional independence scores were similar for the two groups,with 63.5% of cannabis users and 55.8% of non-users having only mild functional disability and just 1.9% and 2.6%, respectively, having significant disability (Rankin score of 4). Two cannabis users and three non-users died during follow up.
“Our data demonstrate that a favorable functional capacity is common in young patients suffering from stroke independently of cannabis use that is likely due to age-related enhanced brain plasticity,” the researchers wrote. “However, in the whole series, 18% of patients retained significant disability, along with 5 deaths.”
Limitations of the study included its single-center design and lack of adjustments for alcohol use, cigarette smoking, or other confounders that may also correlate with cannabis use.
Nevertheless, the researchers concluded that it is important for the public to be made aware of the potential impact of marijuana use and related lifestyle factors on stroke risk.
From the American Heart Association: