Smoking marijuana linked with higher risk of stroke in young adults, study finds

Many who support the legalization of marijuana often tout the drug’s benign side effects, asserting that long-term marijuana use has no lasting impact on an individual’s health.

However, many studies have surfaced that shed doubt on this claim.  Recent research from Duke University in Durham, N.C., found teenagers who smoked marijuana habitually during their adolescence showed a decrease in their general intellectual ability as they progressed into adulthood.

But now, there is an even more chilling possible side effect of cannabis use – an increased risk of stroke.

According to a new study from the University of Auckland in New Zealand, marijuana may double the risk of ischemic stroke and transient ischemic attack (TIA) in young adults – even those who had no risk factors that often contribute to an attack.

The study’s lead author, Dr. P. Alan Barber, a professor of clinical neurology at the University of Auckland, said he was interested in studying the link between stroke and marijuana after a curious incident of stroke occurred in one of his younger patients.

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    “I look after people with strokes,” Barber told, “and we had a patient come in with stroke; they were young, but they didn’t have high blood pressure or high cholesterol, and they were reasonably fit and well.  They were clean from a risk factor point of view, but they had a stroke while smoking marijuana.  So we looked at the literature and saw sporadic stroke reports among marijuana users.”

    Conducting the first case-controlled study of its kind, Barber and his colleagues studied 160 ischemic stroke/TIA patients between the ages of 18 to 55 (an average age of 45), who had their urine samples screened when they entered the hospital.  As a comparison, the researchers examined urine samples of 160 control subjects who had been admitted to the hospital for other medical reasons.

    Of the 160 stroke patients, 16 percent tested positive for marijuana use within the past couple of days, compared to only 8.1 percent of the control patients.  According to Barber, the stroke patients were very well matched to the controls, with no differences in age, mechanisms for stroke or other vascular risk factors.

    While the study provides the strongest evidence ever of the link between cannabis use and stroke, the research does come with a catch.  Of the 16 percent of stroke patients who were marijuana users, almost all of them smoked tobacco regularly.

    “We haven’t been able to tease apart the relationship between cannabis and stroke independent of smoking, because all the cannabis smokers but one who had stroke had smoked cigarettes,” Barber said.  “So we can say cannabis smoking including tobacco smoking is associated with a higher risk of ischemic stroke.”

    Also, Barber noted the urine samples for the control subjects were obtained without the patients’ consent, so the researchers only knew their age, sex and ethnicity.  While he said further research is needed in this area, it’s tricky to get the most accurate results, since marijuana is an illegal substance, and there’s a possibility for a strong risk of bias when studying this connection.  Even though their research comes with some caveats, Barber is fairly certain the relationship between marijuana use and stroke is a causal one.

    “We know people had strokes while using cannabis, meaning there’s a strong temporal association – so it suggested a cause,” Barber said. “We know that cannabis can lead to problems with the heart, such as heart palpitations and atrial fibrillation,” – which can significantly increase a person’s risk of stroke.  “(It also) can lead to restriction of arteries in the brain… and that reduced blood flow, that’s what happens with stroke.”

    This news comes at a time when there is a big push to legalize marijuana for medicinal, and even recreational, purposes. More and more states are considering making the drug legal, following in the footsteps of Washington and Colorado – which recently legalized the possession, transportation and sale of marijuana.

    Currently, stroke is one of the leading causes of death in the United States, killing close to 130,000 Americans each year, according to the Centers for Disease Control and Prevention.  Typically those who experience stroke are over the age of 65, which is why the University of Auckland study is so alarming.

    In light of this research, Barber said people need to take a step back and be a bit more skeptical when it comes to smoking cannabis.

    “There’s a perception by the public that cannabis is relatively benign and a natural high,” Barber said, “…but this study suggests it may not be benign as you think.”