Marijuana users who suffer from a stroke are more likely to have brought the affliction on by stenosis in the skull, when compared to stroke sufferers who do not use marijuana. Researchers from the University Hospital of Strasbourg in Strasbourg, France, explored the differences in the causes of strokes in cannabis and non-cannabis smokers in a bid to better understand the mechanisms of strokes.

They found that strokes that stem from stenosis – or narrowing of the arteries – in the brain are more commonplace in marijuana users. By examining all patients aged 45 and younger who were admitted to the hospital after suffering an ischemic stroke – a stroke caused by a blood clot that blocks the flow of blood to the brain and – which was 334 patients, with 58 of these marijuana users, they found that an ischemic stroke was more likely to be caused by intracranial arterial stenosis for cannabis smokers.

Intracranial arterial stenosis, which is where arteries in the skull narrow due to a build-up of plaque, was found in 45% of marijuana stroke sufferers, compared to just 14% of non-users, according to a report published in the Journal of the American College of Cardiology. Cardio embolism, a blood clot formed elsewhere in the body that travels to the brain, was the most common ischemic stroke cause in non-marijuana users – 29% compared to 14% in marijuana smokers.

The authors wrote in their study: "Fighting stroke must remain a priority, including in young adults. The first step may be to inform the public regarding the potential occurrence of stroke associated with cannabis and other lifestyle risk factors."