Marijuana users’ risk of deadly complication doubles after rare type of bleeding stroke

Marijuana users who have a rare type of bleeding stroke are at significantly increased risk for death compared to people that don’t use marijuana. Additionally, the more they smoke per day and the longer they’ve been using marijuana, the higher their chance is.

Marijuana users' risk of deadly complication doubles after rare type of bleeding stroke



According to new research published today in Stroke, a peer-reviewed journal of the American Stroke Association, a division of the American Heart Association, recent marijuana users were more than twice as likely to develop a dangerous complication that can result in death or greater disability among people with an aneurysmal subarachnoid hemorrhage (aSAH) stroke, a type of bleeding stroke. The research is the biggest to look at the effects of THC, or tetrahydrocannabinol, the psychoactive component of marijuana (which alters a person’s mental state), on complications after an aneurysmal subarachnoid hemorrhage (a uncommon but serious kind of stroke).

An aneurysmal subarachnoid hemorrhage occurs when a weakened and bulging section of a blood artery on the surface of the brain breaks, causing bleeding in the space between the brain and the tissue that covers it (called a ruptured aneurysm). This kind of stroke may be disastrous, with around 66 percent of persons experiencing neurological damage and about 40 percent dying (during the follow-up period). Aneurysmal subarachnoid hemorrhage requires prompt treatment to halt and prevent future bleeding. Despite therapy, many patients may have increasing symptoms in the 14 days after an aneurysmal subarachnoid hemorrhage (such as speech problems or difficulty moving). Blood from the first stroke irritates blood vessels, causing them to contract and shut off blood flow to a part of the brain (a vasospasm), leading in further brain injury. After an aSAH stroke, a condition known as delayed cerebral ischemia is a primary cause of mortality and disability.

“We’re all vulnerable to a bleeding stroke or a ruptured aneurysm,” said Michael T. Lawton, M.D., senior author of the study and president and CEO of Barrow Neurological Institute in Phoenix, Arizona. “However, if you’re a regular marijuana user, you may be predisposed to a worse outcome from a stroke after the rupture of that aneurysm.”

Researchers looked examined data from over 1,000 patients treated at Barrow Neurological Institute for aneurysmal subarachnoid hemorrhage between January 1, 2007 and July 31, 2019. All of the patients were treated to stop the bleeding in one of two ways: 1) open surgery to clip off the aneurysm’s base, or 2) noninvasively, by threading a thin tube through a blood vessel to the aneurysm’s base and releasing coils that fold to fill the space and provide a barrier to further bleeding.

All patients hospitalized with burst aneurysms had their urine toxicology tested. The researchers examined the incidence of delayed cerebral ischemia in 46 persons (average age 47; 41% female) who tested positive for THC (the psychoactive component of cannabis, popularly known as marijuana) with 968 people (average age 56; 71% female) who tested negative for THC. A positive THC urine test indicates that you have used cannabis within the last three days for a single use and within the last 30 days for regular heavy usage.


When compared to individuals who tested negative for THC, recent cannabis users did not have substantially bigger aneurysms or worse stroke symptoms when brought to the hospital, nor were they more likely to have high blood pressure or other cardiovascular risk factors. In comparison to patients who tested negative for THC, recent cannabis users were considerably more likely to test positive for other drugs such as cocaine, methamphetamines, and cigarettes.

Sixty-six percent of the patients got delayed cerebral ischemia, 50 percent suffered moderate to severe impairment, and 13.5 percent died.

Patients who tested positive for THC at the last follow-up were found to be: After controlling for many patient characteristics as well as recent exposure to other illegal drugs, patients who tested positive for THC at the last follow-up were found to be:

  • delayed cerebral ischemia is 2.7 times more likely to occur;
  • Long-term moderate to severe physical impairment is 2.8 times more probable; and
  • It’s 2.2 times more probable that you’ll die.

“When persons with burst aneurysms have a history of cannabis use or test positive on a toxicology screen, it should raise a red signal to the treating team that they are at increased risk of vasospasm and ischemic consequence,” Lawton said.

“Only cannabis, out of all the drugs found in the toxicology test, increased the risk of delayed cerebral ischemia. Because cocaine and meth are hypertensive substances, they are likely to be linked to the rupture, but they are unlikely to cause vasospasm.”

The research doesn’t go into detail on how cannabis might cause vasospasm and delayed cerebral ischemia.

According to Lawton, “Cannabis has the potential to disrupt cellular oxygen metabolization and energy generation. The cells are significantly more prone to alterations that impact the supply of oxygen and the flow of blood to the brain when they are pressured by a burst aneurysm.”

The study’s limitations include the fact that it was done retrospectively at a single institution and that it was not a head-to-head comparison of marijuana users and non-users.

The researchers are now following up in the lab to learn more about THC-related hazards that might affect aneurysm development and rupture. They also call for further research on the effects of different THC dosages on stroke complications.

“Given its popularity and as more states legalize recreational marijuana use, evaluating the dangers and benefits of marijuana usage is increasingly critical,” Lawton said.

“The current study is not a randomized controlled trial, but it is a rigorous statistical analysis involving more than 1,000 patients, so the results are important and add to what we already know about possible adverse effects of marijuana use,” said Robert L. Page II, Pharm.D., M.S.P.H., FAHA, chair of the writing group for the American Heart Association’s 2020 cannabis statement and professor in the department of clinical pharmacy and the department of cardiovascular medicine at the University of Michigan.

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