Two New Studies Link Cannabis to Cardiovascular Problems

Two new studies add to the growing body of evidence linking cannabis to worse cardiovascular health outcomes. Although more research is needed to determine the amount and type of cannabis use, the lead author of both studies said the primary takeaway of the findings is that “legal doesn’t mean safe.”

A retrospective study on the link between cannabis use and heart attacks was published this month in JACC Advances. In addition, a meta-analysis — the largest pooled study to assess heart attacks and cannabis use according to the American College of Cardiology — will be presented on March 29 at the group’s annual scientific meeting.

Killer Buzz?

To assess the effects of cannabis use on heart health, researchers analyzed data from approximately 4.6 million patients in the United States, Canada, and the European Union using the TriNetX Research network.

From this group, researchers identified two cohorts: Self-reported cannabis users and nonusers. The average age of participants in the study was 25 years. The study participants selected had no reported comorbid conditions that increased their risk for heart attack.

The cohorts were matched according to age, sex, race, family history of heart attack, and health markers including creatinine, low-density lipoprotein, blood sugar levels, systolic blood pressure, and body mass index.

Compared with people who said they did not use cannabis, those who reported using the drug had a sixfold increased risk for heart attack, a fourfold increased risk for ischemic stroke, double the risk for heart failure, and three times the risk for cardiovascular death, heart attack, or stroke. The patient records lacked enough data for the researchers to determine how much cannabis use is dangerous for the heart or if certain methods of use — smoking, vaping, or ingesting — are riskier than others, they said.

“We studied healthy, young adults. If they had this significant risk, I would speculate that the risk of cannabis would be higher in patients with hypertension and older patients,” said the study’s lead author Ibrahim Kamel, MD, MHA, a clinical instructor at the Boston University Chobanian & Avedisian School of Medicine and internal medicine resident at Boston’s St. Elizabeth’s Medical Center, Boston.

Kamel said he and his colleagues performed a sub-analysis that found cocaine and alcohol use did not alter the findings. (Kamel and his team plan on publishing these results separately.)

About 50% More Heart Attacks

In addition to the retrospective study, Kamel is also the lead author of a meta-analysis, which pooled 12 previously published studies, 10 from the United States, 1 from Canada, and 1 from India.

Seven of the studies linked cannabis use to an increased risk for heart attack, and four showed no significant difference. One found a lower risk for heart attack among cannabis users. Overall, those who used cannabis were 1.5 times more likely to experience a heart attack than were people who said they did not use the drug.

The meta-analysis was unable to account for tobacco use, the use of other substances, nor the duration or type of cannabis use. The average age of the study participants among the pooled studies that included this information was 41 years.

Kamel said many of the 12 studies hypothesized endothelial dysfunction and impaired blood flow as a potential mechanism for how cannabis might affect the cardiovascular system.

The theory that endothelial dysfunction may be to blame is supported by the fact that most of the heart attacks among those who used cannabis in the studies “were thrombotic in nature” and not due to “the usual plaque rupture,” Kamel said.

Kamel thinks cannabis products should include warnings about their potential cardiovascular risks, much like those on cigarette packages. “We shouldn’t be expected to prove that cannabis use is harmful,” he said. “The industry should have to prove that cannabis use is safe.”

Even with the implementation of warning labels and education campaigns, Kamel added, “physicians should have a frank discussion with their patients, explaining that we don’t know for a fact that cannabis use causes heart disease, but the evidence is growing. Patients should be informed.”

The study was independently supported. The authors reported no relevant financial relationships.