Study Examines How Cannabis Use Affects Heart Disease

Two new studies presented at the American Heart Association’s Scientific Sessions raise some red flags for people with heart disease but show the need for more research into the effects of cannabis, according to NBC News.

The first study looked at data from 113,477 Michigan patients. After identifying 3,903 who were cannabis “smokers,” the researchers paired them with the same number of cannabis “non-smokers.” The analysis found bleeding post-angioplasty occurred in 5.2% of smokers, compared to 3.4% of non-smokers. A closer look at stroke victims within the group showed a similar pattern when comparing smokers to non-smokers, 0.3% to 0.1%. The researchers, however, also found that cannabis smokers in the cohort were less likely to have sudden kidney failure — and were unable to explain why.

“Marijuana is becoming more accessible, and patients should be aware of the increased risk after angioplasty. While these are risks to be aware of, they shouldn’t deter patients from obtaining this lifesaving procedure.” — Dr. Sang Gune Yoo, internal medicine resident at the University of Michigan, via NBC News

Similar to the first study, the second study had unexpected results. This study used data from a national database and found that 7.2% of patients who had an artery clearing procedure after a heart attack and identified as cannabis smokers had a second heart attack, compared to 4.5% of non-smokers. The twist, according to the report, is that patients who used cannabis had lower heart attack risk factors like hypertension, diabetes and high cholesterol.

Dr. Deepak Cyril D’Souza, a professor of psychiatry at the Yale University School of Medicine, told NBC News, “I have spent the last 25 years studying the effects of marijuana and THC and I think the Yoo study raises some important questions, especially since we’ve seen more and more reports of cardiovascular events occurring in the context of marijuana.”

Doctors do not know if it is the cannabis, THC in the cannabis, or the burning plant matter that is leading to these issues, although Dr. D’Souza says numerous other studies show THC does raise heart rate and blood pressure. Researchers do agree on the need for more research into cannabis, which today is hampered by the plant’s designation as a Schedule I narcotic.

Dr. Peter Grinspoon — an instructor at Harvard medical school, cannabis expert, and board member for Doctors for Cannabis Regulation — is intrigued by the contradictory findings of the two papers.

“Looking at the totality of the two studies, they seem to contain some contradictory findings,” Dr. Grinspoon told NBC News. “By their measures, they’ve actually shown that cannabis decreases kidney damage, which should be a huge headline in itself.”