Houston, Texas, USA : New research is being presented at the World Stroke Congress in Montreal, Canada today linking recreational cannabis use with an increased risk of stroke.
The study, being outlined at the World Stroke Congress, looked at five years of hospital statistics from the United States.
Review of U.S. hospital statistics shows rise in stroke incidence among marijuana users from 2010-14 while overall stroke prevalence remained stable
A five-year study of hospital statistics from the United States shows that the incidence of stroke has risen steadily among marijuana users even though the overall rate of stroke remained constant over the same period.
The study, presented today during the third day of the World Stroke Congress in Montreal, looked at U.S. hospital statistics from 2010 to 2014. It examined a total of 2.3 million hospitalizations among people who used marijuana recreationally. Of these, 32,231, or 1.4 percent, had a stroke including 19,452 with acute ischemic stroke (AIS).
Over the five years studied, the rate of stroke of all types among marijuana users increased from 1.3 percent to 1.5 percent. The rate of AIS increased from 0.7 percent to 0.9 percent. During the same five-year period, the prevalence of stroke among all patients was stable.
As result, the researchers conclude that these growing trends of stroke among marijuana users “warrant further prospective studies to evaluate the marijuana-stroke association amidst legalization of recreational use.”
The researchers noted in introducing their study that marijuana “has a potential link to stroke owing to cerebrovascular effects of cannabinoids.”
They say their findings make a case for “further prospective studies to evaluate the marijuana-stroke association amidst legalization of recreational use.”
The risk for any stroke could increase by 15 percent and it could jump 29 percent for an ischemic stroke — the most common kind, said lead investigator Dr. Krupa Patel. She is a research physician at Avalon University School of Medicine in Willemstad, Curacao.
Patel cautioned that the study can’t prove that using marijuana causes strokes, only that the two are associated.
“We can’t establish causation, but what we can say is that recreational marijuana users are at higher risk in terms of stroke,” she said.
In addition, the researchers don’t know if the risk is tied to smoking marijuana or ingesting it in other ways, and whether it depends on the amount of the drug used or if it is due to other psychoactive ingredients mixed in with the marijuana.
Patel said the risk may be exacerbated by chronic medical conditions of the marijuana users who had strokes, such as diabetes or obesity.
Also, the researchers could not tell from the data whether marijuana users used other drugs like cocaine or smoked tobacco, she said.
Still, more strokes occurred among marijuana users than nonusers, which leaves open the question of what accounts for the increase in risk.
“At this point we can just say there is this increased risk,” Patel said.
The best way to sort out whether marijuana is truly associated with an increase in stroke is in a clinical trial, said Dr. Thalia Field, an assistant professor of neurology at the University of British Columbia in Vancouver.
“It’s too early to say that this is causative,” she said. “It has to be borne out in other studies.”
Paul Armentano, deputy director of the marijuana advocacy group NORML, said, “This finding is inconsistent with other population-based studies, which failed to identify cannabis as an independent risk factor for stroke in younger subjects.”
NORML, however, recognizes that the data on this subject is evolving and that cannabis smoke can cause a cardiovascular response, he added.
People with a history of heart disease or stroke may be at an increased risk for adverse side effects from marijuana, particularly smoked cannabis, Armentano acknowledged.
“As with any drug, people should consult their doctor before deciding whether the medical use of cannabis is safe and appropriate,” he said.
A separate study also linked marijuana use to increased risk of stroke:
Evidence linking marijuana and risk of stroke grows
Smoking marijuana may increase your chances of having a stroke, according to a review of 34 different studies published in the American Heart Association’s journal Stroke.
Researchers found a link between marijuana use and stroke in a total of 64 stroke patients (80 percent men, average age 32). They also found:
81 percent of the stroke patients suffered a stroke or mini-stroke within 24 hours following marijuana use.
About one in four stroke patients suffered another stroke after repeated marijuana use.
Half of those who had stroke also had other stroke risk factors—most commonly tobacco or alcohol use.
Three quarters of the patients (48 out of 64) underwent toxicological analysis for common street drugs; results were positive for drugs other than marijuana in only two cases.
It’s “striking” that more strokes are not seen given the broad use of marijuana by the general public, researchers said. They suggest this may be due to variations in dosage, frequency of use, strength of marijuana, person’s genetic makeup and other drugs taken along with the marijuana.
It is also possible that patients don’t tell their doctors that they have used marijuana or that the exposure is overlooked.
Since recent studies support a link between marijuana use and stroke; doctors need to be aware of this association especially when dealing with younger stroke patients who may reuse marijuana after stroke.
A third study linked smoking marijuana with higher stroke risk in young adults:
Smoking marijuana associated with higher stroke risk in young adults
Marijuana, the most widely used illicit drug, may double stroke risk in young adults, according to research presented at the American Stroke Association’s International Stroke Conference .
In a New Zealand study, ischemic stroke and transient ischemic attack (TIA) patients were 2.3 times more likely to have cannabis, also known as marijuana, detected in urine tests as other age and sex matched patients, researchers said.
“This is the first case-controlled study to show a possible link to the increased risk of stroke from cannabis,” said P. Alan Barber, Ph.D., M.D., study lead investigator and professor of clinical neurology at the University of Auckland in New Zealand. “Cannabis has been thought by the public to be a relatively safe, although illegal substance. This study shows this might not be the case; it may lead to stroke.”
The study included 160 ischemic stroke/TIA patients 18-55 years old who had urine screens upon admission to the hospital. Among the patients, 150 had ischemic stroke and 10 had TIAs. Sixteen percent of patients had positive drug screens, mostly male who also smoked tobacco.
Only 8.1 percent of controls tested positive for cannabis in urine samples. Researchers found no differences in age, stroke mechanism or most vascular risk factors between marijuana users and non-users.
In previous case reports, ischemic stroke and TIAs developed hours after cannabis use, Barber said. “These patients usually had no other vascular risk factors apart from tobacco, alcohol and other drug usage.”
It’s challenging to perform prospective studies involving illegal substances such as cannabis because “questioning stroke and control patients about cannabis use is likely to obtain unreliable responses,” Barber said.
In the study, the regional ethics committee allowed researchers to use urine samples from other hospitalized patients. But researchers knew only the age, sex and ethnicity for matching due to a lack of consent.
The study provides the strongest evidence to date of an association between cannabis and stroke, Barber said. But the association is confounded because all but one of the stroke patients who were cannabis users also used tobacco regularly.
“We believe it is the cannabis and not tobacco,” said Barber, who hopes to conduct another study to determine whether there’s an association between cannabis and stroke independent of tobacco use. “This may prove difficult given the risks of bias and ethical strictures of studying the use of an illegal substance,” he said. “However, the high prevalence of cannabis use in this cohort of younger stroke patients makes this research imperative.”
Physicians should test young people who come in with stroke for cannabis use, Barber said.
“People need to think twice about using cannabis,” because it can affect brain development and result in emphysema, heart attack and now stroke, he said.