Marijuana Update: More than 2 Million Patients with Heart Disease Have Used the Drug

A new review published in the Journal of the American College of Cardiology indicated that more than two million people with heart disease have used marijuana.

“Now that we have seen marijuana use become more popular than tobacco smoking, we need more rigorous research, including randomized clinical trials, to explore the effects of marijuana on cardiovascular health,” review co-author Muthiah Vaduganathan, MD, MPH, of Brigham and Women’s Hospital’s Heart and Vascular Center, said in a press release. The finding that millions of patients have used the substance (shown by national survey data) was part of a review of marijuana use in patients with established cardiovascular disease.

The researchers pointed out that marijuana use, in addition to carrying similar hazards of cigarette use, can also lead to unintended interactions with other medications. Cannabinoid receptors, they noted, have been shown to disturb some tissue beds and cells (platelets, adipose tissue, and myocytes). They also noted that there have been relatively few randomized clinical trials looking at the effects of marijuana use on cardiovascular risk.

Limited Data, But Some Suggested Interactions

The reviewers focused on five main highlights for the public presentation of their study.

1. Two Million People with Heart Disease Have Used Marijuana

Current estimates show that around 90 million Americans have used marijuana in their lifetime, and more than 39 million within the previous year. Data from the National Health and Nutrition Examination Survey (NHANES) from 2016 suggested to the authors that about 2 million patients who currently have heart disease reported using the drug recently or at any time in the past.

2. Cannabinoids Can Interact with Heart Medication

Cannabinoids, which are commonly found chemical compounds in marijuana, have been shown in some cases to inhibit certain enzymes, thereby affecting metabolism. This affects the body’s ability to process other medications that are used to treat heart disease (including antiarrhythmics, statins, calcium-channel blockers, beta-blockers, and warfarin). Receptors for cannabinoids can be found in the nervous system, blood cells, muscle cells, and other tissues. The authors acknowledged the limited data for these findings.

3. Potency of Today’s Marijuana is Higher

In the past, the potency of marijuana was much lower than it is today. Modern marijuana is much more potent than marijuana from 30 years ago, partially as a result of refined cultivation and growth methods. The average THC concentration in the mid-1990s was around 4%, which has increased to around 12% in 2014. Most studies in the analysis tested THC levels between 1.5% and 4%.

4. Possible Link to Heat Attacks and Stroke

Some studies suggest that smoking marijuana could trigger heart attacks in at-risk populations. “Though current evidence for a link between marijuana and heart attacks is modest, it’s thought that smoking marijuana may increase cellular stress and inflammation, which are known to be precipitating factors for coronary artery disease and heart attacks,” a press release noted. “Cerebrovascular events, including strokes, also have been associated with marijuana use. It’s thought that marijuana may induce changes in the inner lining of blood vessels or alter blood flow.”

5. Clinical Screening is Recommended

Based on the limited data that are available, the authors recommended that clinicians screen for marijuana use as part of general practice. Screening could include conversations about past or present use, or toxicology testing.