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Association is stronger when marijuana use is frequent.

As the decriminalization of marijuana becomes more widespread, its use is on the rise among young adults. Yet, the effects on overall health have not been well studied, including how marijuana use affects cardiovascular health.

Now a large-scale study in the Canadian Medical Association Journal has found an association between recent marijuana use and increased risk of myocardial infarction (MI) in young people, ages 18 to 44 years. The association was strongest among those who used marijuana at least four times a month, primarily by smoking it. Users who vaped or ingested marijuana through baked goods or other edibles also had a higher incidence of MI compared with nonusers, but only those who smoked frequently showed elevated risk that was statistically significant.

The study was based on 2017 and 2018 behavioral risk survey data from the Centers for Disease Control and Prevention. It sought to evaluate known evidence of cardiovascular effects of marijuana in the context of MI risk for individual users. Marijuana’s chemical components can increase myocardial oxygen demand while simultaneously reducing blood flow to the myocardium. This cannabis-induced oxygen supply and demand mismatch, in the setting of myocardial dysfunction, may be the mechanism for acute MI, the researchers suggested.

Study does not demonstrate causality, but large sample size suggests a link.

Of 33,173 people in the study cohort, 4,610 (17.5%) reported using marijuana in the past 30 days. Of these, 1.3% reported a history of MI, compared with 0.8% of nonusers. Smoking was favored by more than three-quarters (76.3%) of the marijuana users, and most (70.5%) reported frequent use, defined as more than four times in the past 30 days. Another 11.3% reported vaping, and the remainder consumed marijuana-laced edibles.

Although the study does not demonstrate causality, its large sample size suggests a link. Nurses caring for young adult patients with chest pain and a known history of marijuana use should consider the possibility of MI. Nurses should also ask any patient with chest pain about marijuana use, including those consuming edibles since data show this group accounts for a significant number of ED visits for cardiovascular symptoms.

—Joan Zolot, PA

 Ladha KS, et al. CMAJ 2021;193(35):E1377-E1384.

You can find a version of this article and other news stories in our December issue, including articles on improving discharge procedures, informed consent and decision-making in high-risk surgery, and a world health roundup. All are currently free to read.