Marijuana is known to be linked with stroke. A new study published in the Journal of the American College of Cardiology suggests that it causes a different kind of stroke than in non-marijuana users.

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Marijuana users are at risk of stroke caused by arterial stenosis.

The new study, the first to investigate differences in stroke between marijuana users and non-users, found that ischemic strokes in young adults who use marijuana are more likely to result from stenosis, or narrowing of the arteries in the skull, than strokes in non-users.

Marijuana is the most commonly used illicit drug in the US. It consists of dried leaves, flowers, stems and seeds from the hemp plant, Cannabis sativa. These contain the mind-altering chemical delta-9-tetrahydrocannabinol (THC) and other related compounds.

Use is widespread among young people, growing numbers of whom believe that it is not dangerous.

With four US states and DC having legalized marijuana for recreational use, and 19 other states legalizing marijuana in some form, the National Institute on Drug Abuse (NIDA) state that it is "particularly important for people to understand what is known about both the adverse health effects and the potential therapeutic benefits linked to marijuana."

Fast facts about marijuana
  • 22.2 million people reported using marijuana in the past month in 2014
  • 2.6 million used it for the first time during the past month
  • Average age of first use was 18.5 years, among users aged 12-49.

Learn more about marijuana

As a medication, clinical trials are currently taking place to investigate the use of cannabinoids to treat conditions such as multiple sclerosis; and there are already two preparations approved by the Food and Drug Administration (FDA) involving THC.

Ischemic stroke is caused by a blockage that interrupts or reduces blood flow to the brain, as opposed to hemorrhagic stroke, which occurs when a blood vessel in the brain leaks or ruptures.

Two causes of ischemic stroke are intracranial arterial stenosis - when plaque builds up and narrows the arteries inside the skull - and cardioembolism - where a blood clot forms in the body and moves to the brain.

The researchers, from the University Hospital of Strasbourg in France, led by Dr. Valerie Wolff, PhD, looked at all patients under age 45 admitted with ischemic stroke from 2005-2014 to create a cohort of 334 patients, including 58 who were marijuana users.

Intracranial arterial stenosis more common in marijuana users

Ischemic stroke in marijuana users was more likely to be caused by intracranial arterial stenosis. Cardioembolism was the most common cause of ischemic stroke in non-marijuana users.

In marijuana users, 45% of strokes were caused by intracranial arterial stenosis, and 14% by cardioembolism; in non-marijuana users, 14% were caused by intracranial arterial stenosis and 29% by cardioembolism.

Marijuana users in the study were younger, more likely to be male, to smoke tobacco, and to have other lifestyle risk factors than non-users in the study.

The authors say:

"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."

Dr. Valentin Fuster, PhD, JACC editor in chief, commented that while the effects of cannabis are often considered benign, there is increasing evidence that its use is related to stroke.

Health risks of marijuana

According to the NIDA, marijuana has long-term or permanent effects on brain development, especially among teens, including how the brain builds connections between areas needed for thinking, memory and learning; this can lead to lower achievement in education.

Use has also been linked to symptoms of mental illness, including temporary hallucinations and paranoia, and worsening of symptoms of schizophrenia.

If a mother smokes during pregnancy, there is a higher risk of fetal and infant developmental and behavioral problems.

Physical effects include breathing and lung problems similar to those of tobacco, and elevated heart rate, which could lead to a heart attack.

Moreover, the increasing amount of THC in marijuana over the past few decades is believed to increase the risk for addiction.

Medical News Today recently reported that marijuana use in the US has doubled since 2001.