What are they smoking? CNN says study found cannabis could double heart attack risk – but did it?

Scientifically reviewed by Codi Peterson, PharmD

Can cannabis really double the risk of a heart attack?

The CNN headline could hardly have been more alarming if it tried: “Young adult cannabis consumers nearly twice as likely to suffer from a heart attack, research shows.” But is that what the research found? A closer look at the study may present more questions than answers.

CNN reported that the study published Tuesday in the Canadian Medical Association Journal concluded that adults under 45 years old who reported frequent cannabis use in the previous 30 days suffered nearly double the number of heart attacks as their peers who don’t use cannabis.

But is that what the study found? Look no further than the 7th paragraph of the CNN article, where the lead author of the study is quoted as saying that the study “did not research how cannabis affects heart health.”

The author, Dr. Karim Ladha, then describes how prior research showed how cannabis can affect heart rate and can increase the amount of oxygen the heart needs – and limit how much oxygen reaches the heart.

“What you end up having is this mismatch of oxygen supply and demand which fundamentally leads to heart attacks,” Ladha said.

Mainly though, the study itself is simply not that ironclad in it’s assertions, like the CNN headline would have you believe. The researchers wrote that the study provides evidence there could be an association between recent cannabis use and a history of myocardial infarction (MI) in young adults, and that “increasing cannabis use in an at-risk population could have negative implications for cardiovascular health.”

One interesting detail left out of the CNN report is that unmarried respondents were more likely to report recent cannabis use – 68% vs 46.4%. Frequent cannabis users were also more likely to be male. According to the study, frequent cannabis use was defined as using it more than four times in the past 30 days.

An aspect of the study that was not covered in the CNN report is the fact that the researchers found that smoking cannabis was by far the most popular form of consumption (76.3%), and smoking cannabis was associated with a higher history of myocardial infarction relative to non-users.

“Although a similarly elevated odds of history of heart attack was observed across methods of recent cannabis consumption, only smoking as a primary method achieved statistical significance,” the researchers wrote. In other words, yes heart attacks were associated with smoking cannabis, but other ingestion methods like vaporization and edibles were not found to significantly correlate with heart attacks.

The CNN report also drew criticism from Brett Puffenbarger, managing partner of Good Highdeas and Director of Sales and Marketing at the Foundation of Cannabis Unified Standards.

In a LinkedIn post this week, Puffenbarger said of the study “the problem is…there was no actual research, and the findings are anecdotal at best.”

Puffenbarger points to how the CNN report reveals that the study’s results came from a self-reported survey and not an actual medical study, and that there were 4,610 cannabis smokers out of 33,173 participants. This is not a small number, but considering there are millions of frequent cannabis users around the world, it’s not a large sample size either.

In addition, the quantitative difference between the cannabis users who had heart attacks – 1.3% – and the 0.8% of non-users who experienced heart attacks was small enough to be “within the margin of error for nearly any survey or polling data.” That being said, these results are statistically significant even when accounting for other variables like income, education, and tobacco use.

He also stated that the assertion that the 1.3% “later had a heart attack” indicates “that there could be no relationship since they may or may not occur simultaneously or as a result of use… that’s called correlation, not causation.”

Puffenbarger added “this is nothing short of clickbait.”

The researchers actually do cover some of these issues in the “limitations” section of the study. They write that they were not able to differentiate between participants who started using cannabis before having an MI and those who began using cannabis after experiencing an MI. The researchers then attempt to shore up their findings by highlighting previous research on THC and heart disease: “However, the plausibility of our association is strengthened by a similar association between recent cannabis use and history of stroke from the same data set.”

They also note that they did not collect data on the use of cocaine and other illicit substances, the chemical composition of the cannabis products used by respondents, or information on cardiovascular confounders among the respondents.

The research failed to collect detailed information on the type of MI, extent of myocardial necrosis and plasma levels of cardiac biomarkers, information which the researchers state “could be important for understanding differences in clinical outcomes, and would provide greater insight on the potential mechanism(s) leading to cannabis-induced MI.”

Moreover, the type of study used is often criticized for producing low-grade evidence. Results from surveys like these that support the use of cannabis are typically dismissed as weak evidence by the medical establishment.

At The Cannigma we are committed to a science-forward approach, accepting both the good and the bad of cannabis research. In this case, it seems smoking cannabis regularly may be associated with a higher risk of experiencing a heart attack. The problem with CNN’s coverage is a bombastic headline that appears to mislead the reader and misconstrue the weight of the research.

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