Heavy marijuana use linked to heart problems in HIV-positive people

HIV-positive people are generally at heightened risk for cardiovascular disease because of a number of contributing risk factors, including the following:

  • high rates of smoking and/or substance use
  • abnormal levels of cholesterol and triglycerides in the blood
  • elevated levels of inflammation
  • insufficient exercise

Furthermore, some studies suggest that marijuana use is relatively common among HIV-positive people. Also, some studies suggest that the use of this herb may contribute to cardiovascular disease in HIV-negative people. It is possible that the same may be true of marijuana use by HIV-positive people.

Researchers at Harvard University conducted an observational study with 558 HIV-positive men between 1990 and 2010. They found that “heavy” marijuana use increased the risk for complications of cardiovascular disease—including heart attack and stroke—regardless of whether the men also smoked tobacco and regardless of the presence of other traditional risk factors.

Study details

The researchers used the database of a study called MACS (Multicenter AIDS Cohort Study), which has been ongoing for many years.

Participants visited study clinics every six months where they underwent interviews and physical examinations and had blood and other fluids collected for analysis.

There are thousands of participants in MACS and researchers excluded from their analysis people with hepatitis C virus (HCV) co-infection as well as people who used other substances such as cocaine and heroin because they wanted to try to focus on the effect of marijuana.

Based on participants’ disclosure, researchers placed them into the following categories:

  • heavy users – daily or weekly use at 50% or more of study visits
  • occasional users – used marijuana less frequently than once a month
  • non-users

Participants who disclosed smoking at least a quarter of a pack of cigarettes daily were classified as “heavy” tobacco users by the researchers.

At the start of the study, participants were an average of 41 years old and about 20% were classified as heavy marijuana users.

Researchers focused on what they called “cardiovascular events,” which included heart attacks, stroke, heart pain, heart failure and related events.


After taking into account many factors, researchers found the following associations:

  • heavy marijuana use was linked to a 2.5-fold increased risk of a cardiovascular event
  • participants who used both marijuana and smoked tobacco had a nearly five-fold increased risk of a cardiovascular event

These associations were statistically significant.

Blood cells

Other studies, with HIV-negative people, have found an association between having elevated white blood cells (WBC) and serious cardiovascular disease. In the present study, participants who were marijuana or tobacco users generally had increased WBC. Furthermore, participants (regardless of substance used) who had a WBC of 6,500 cells/mm3 or greater had a four-fold increased risk for a cardiovascular event.

Other issues

There was no significant association between long-term heavy marijuana use and changes in viral load, CD4+ cell count, the risk for developing AIDS, cancer or death. In contrast, cigarette smokers had an increased risk for both heart attack and cancers unrelated to AIDS.

Bear in mind

The present study found associations between heavy marijuana use and an increased rate of cardiovascular events in men aged 40 to 60 years. This increase was independent of smoking tobacco.

Additional studies will be needed to uncover the reason(s) for this association between heavy marijuana use and cardiovascular events.

The present study is observational in design. Such studies cannot prove that marijuana (or anything else) caused cardiovascular events. However, the present study provides a foundation for further investigating any connections between cardiovascular health, marijuana use and HIV. Such future studies need to include women and ask at least the following questions:

  • Which strains of marijuana were used?
  • What was the relative mix of cannabinoids in such strains?
  • How was marijuana used—smoked, ingested (edibles) or vapourized?
  • How much marijuana was used and how often?
  • Did marijuana interact with ART and/or other medicines commonly used by co-infected people?
  • Are there differences in the effect of marijuana by gender?

—Sean R. Hosein


  1. Pacher P, Steffens S, Haskó G, et al. Cardiovascular effects of marijuana and synthetic cannabinoids: the good, the bad, and the ugly. Nature Reviews. Cardiology. 2018 Mar;15(3):151-166.
  2. Lorenz DR, Dutta A, Mukerji SS, et al. Marijuana use impacts midlife cardiovascular events in HIV-infected men. Clinical Infectious Diseases. 2017 Aug 15;65(4):626-635.