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Questionable Association Between Cannabis Use and Myocardial Infarction

The Canadian Medical Association Journal published an article on the potential dangers of cannabis use and myocardial infarction in young adults. The authors, Ladha and colleagues, concluded that there is an association between recent cannabis use and history of myocardial infarction (MI), particularly if those users smoke cannabis. Tetrahydrocannabinol (THC), one of the most abundant compounds found in cannabis plants, is known to cause tachycardia and there has been a long-standing debate about the link between excessive cannabis use and ischemic stroke, but this would be the first study to establish a firm link between cannabis use and MI.

The study, which involved 33,173 adults between 18 and 44 years of age from the United States, did find an association between cannabis use and MI. Of the 28,563 non-cannabis users analyzed, 240 (0.8%) reported a history of MI, while 61 (1.3%) of the 4,610 cannabis users reported a history of MI. A secondary analysis found that a history of MI was more common among frequent cannabis users (defined as more than 4 times within the last 30 days) when compared to non-frequent users, and that smoking cannabis was more strongly associated with a history of MI than other delivery methods (vaporization or the consumption of edible cannabis products). In fact, the link between history of MI and use of vaporization or edibles was not statistically significant.

That said, the study has many limitations that would suggest the association is far from definitive. For example, the percentage of cannabis users who reported heavy alcohol use was more than three times that of the group of non-cannabis users (1,691 (5.2%) vs. 862 (17.4%)), and the percentage of current combustible cigarette smokers among cannabis users was more than double that of the non-cannabis group (4,376 (13.2%) vs. 1,770 (31.6%)). As heavy alcohol consumption and cigarette smoking are associated with increased risk of heart disease, these confounding factors could be influencing the data. These kinds of variables need to be accounted for to establish a firm link between cannabis use and MI.

The CMAJ has more.

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