The analysis, published on January 6 in the journal Stroke, is the largest to study the impact of THC, the substance in marijuana responsible for changes in mood and mental state, on complications after a bleeding stroke. “We’re all vulnerable to a bleeding stroke or a ruptured aneurysm; however, if you’re a routine marijuana user, you may be predisposed to a worse outcome from a stroke after the rupture of that aneurysm,” said Michael T. Lawton, MD, the senior author of the study and the president and CEO of Barrow Neurological Institute in Phoenix, in an American Heart Association release.
Marijuana Use by Older Adults Is on the Rise
It’s estimated that 48.2 million people, or about 18 percent of Americans, used marijuana at least once in 2019, according to the Centers for Disease Control and Prevention (CDC). There are now 36 states and four U.S. territories that allow for the medical use of marijuana, and 18 states and two territories that allow the recreational use of the drug, according to the National Conference of State Legislatures (NCSL). A study published in the Annals of Internal Medicine in January 2021 that looked at cannabis use in 171,507 adults age 55 and up between 2016 to 2018 found that men ages 60 to 64 reported the highest rates of marijuana use, with 12.6 percent of those surveyed in 2018 saying they had used the drug in the previous 30 days, up from 8.9 percent in 2016. Over the same time period, use almost doubled in men between ages 65 and 69, rising from 4.3 percent in 2016 to 8.2 percent in 2018, and among men ages 70 to 74, from 3.2 percent to 6 percent. The authors reported less change in marijuana use among women.
What Is an Aneurysmal Subarachnoid Hemorrhage (aSAH) and What Are the Complications?
In this type of stroke, bleeding occurs in the space surrounding the brain when an aneurysm (a weak area in a blood vessel) on the surface of the brain bursts and leaks. This causes a buildup of blood around the brain and inside the skull, resulting in increased pressure on the brain. There are about 30,000 new cases of aneurysmal subarachnoid hemorrhage in the United States every year, and it causes neurological disability in approximately two out of three people and death during the follow-up period in about two in five people. After the immediate treatment, which is to stop and prevent further bleeding, many people experience a complication called cerebral ischemia within two weeks after the event. This happens when blood from the initial stroke irritates blood vessels, causing them to constrict enough to cut off the supply of blood to a portion of the brain, resulting in more brain damage and, in many people, death or disability.
Marijuana Use More Than Doubled the Risk of aSAH Stroke Complication
Researchers analyzed data from 1,014 people who had been treated for aneurysmal subarachnoid hemorrhage at Barrow Neurological Institute in Phoenix between January 1, 2007, and July 31, 2019. All patients had been treated to stop the bleeding, either with an open surgery to clip off the base of the aneurysm or noninvasively with a slim tube threaded through a blood vessel to the base of the aneurysm, releasing coils that fold to fill in the space and provide a barrier to further bleeding. The study compared the occurrence of delayed cerebral ischemia in 46 people (27 men and 19 women) with an average age of 47 years who tested positive for THC with 968 people with an average age of 56 who tested negative for THC. A positive urine screen for THC reflected cannabis exposure within three days for a single use and within approximately 30 days for frequent heavy use. Compared with people who hadn’t used marijuana in the previous month, the recent cannabis users did not have significantly larger aneurysms or worse stroke symptoms when admitted to the hospital, and the two groups had similar cardiovascular risk factors. But recent cannabis users were significantly more likely to also test positive for other substances, including cocaine, methamphetamines, and tobacco, compared with the patients who screened negative for THC. Among all participants, 36 percent developed delayed cerebral ischemia, 50 percent were left with moderate to severe disability; and 13.5 percent died. After adjusting for age, sex, preexisting health conditions, and tobacco smoking, as well as recent exposure to other illegal substances, the group who tested positive for THC at last follow-up were found to be:
2.7 times more likely to develop delayed cerebral ischemia — 52.2 percent of those with recent cannabis use compared with 35.5 percent with no recent cannabis use2.8 times more likely to have long-term moderate to severe physical disability2.2 times more likely to die
“When people come in with ruptured aneurysms, and they have a history of cannabis use or are positive on a toxicology screen, it should raise a red flag to the treating team that they are at higher risk of vasospasm and ischemic complication,” Dr. Lawton said. Vasospasm occurs when a brain blood vessel narrows, blocking blood flow. “Of all the substances detected in the toxicology screen, only cannabis raised the risk of delayed cerebral ischemia. Cocaine and meth are hypertensive drugs, so they are likely related to the actual rupture but not expected to have an impact on vasospasm.”
Authors Speculate That Marijuana May Impair Oxygen Metabolization
The study was not set up to discover how cannabis use may raise the risk of vasospasm and delayed cerebral ischemia, but the authors have a few theories. “Cannabis may impair oxygen metabolization and energy production within cells. When stressed by a ruptured aneurysm, the cells are much more vulnerable to changes that affect the delivery of oxygen and the flow of blood to the brain,” says Lawton. The authors acknowledge that the findings are limited because the analysis was performed retrospectively and at a single institution (rather than at several hospitals across the country). Laboratory research by the authors is ongoing as they seek to better understand THC-related risks that may impact aneurysm formation and rupture.
