Cannabis has complex heart effects: THC may increase heart attack risk while CBD may be protective | Research

The takeaway

A review of drugs of abuse and heart failure found that THC can increase sympathetic tone and vascular dysfunction, potentially increasing myocardial infarction risk, while CBD shows cardioprotective properties in preclinical studies.

Cardiologists, heart failure specialists, patients with cardiac conditions who use cannabis

THC increases sympathetic tone and MI risk; CBD is cardioprotective in preclinical studies

What the researchers found

Cannabis has complex cardiovascular effects depending on consumption method, amount, and cannabinoid content. THC can increase sympathetic tone, cause vascular dysfunction, and may increase myocardial infarction risk. CBD is cardioprotective in preclinical studies and is a potential therapeutic target. The effects are complicated by the interaction between these opposing cannabinoid profiles.

Why it matters

Heart failure patients may use cannabis, and clinicians need to understand the opposing cardiovascular effects of THC and CBD to provide appropriate guidance, especially as legal access increases.

The numbers in context

THC: increases sympathetic tone, causes vascular dysfunction, may increase MI risk; CBD: cardioprotective in preclinical studies; effects vary by consumption method, dose, and cannabinoid content

How the study worked

Narrative review of the cardiovascular effects of alcohol, tobacco, cannabis, and cocaine on heart failure development and outcomes.

What this study cannot tell us

Narrative review with limited cannabis-specific clinical trial data. Most evidence is preclinical for CBD cardioprotection. Cannabis cardiovascular research is confounded by tobacco co-use. Heart failure-specific cannabis data are sparse.

How to read the evidence

Comprehensive narrative review drawing from multiple evidence sources, but limited cannabis-specific clinical data.

When this study was published

Published in 2021.

The bigger picture

The opposing cardiovascular effects of THC and CBD suggest that the net cardiac risk of cannabis use depends heavily on the product's cannabinoid ratio, which varies enormously across products and is rarely known by consumers.

Questions still open

Would CBD-dominant products be safe or even beneficial for heart failure patients? Should THC-dominant products carry specific cardiovascular warnings?

Common questions

Is cannabis bad for the heart?

It depends on the cannabinoid. THC can increase heart rate, sympathetic activation, and vascular dysfunction, potentially increasing heart attack risk. CBD appears to be cardioprotective in animal studies. The net effect depends on the product's THC-to-CBD ratio.

Can people with heart failure use cannabis?

The review suggests caution, particularly with THC-dominant products. CBD's potential cardioprotective effects are promising but based on preclinical data. Clinicians should assess cardiovascular risk when counseling patients about cannabis use.

Read the original research

Drugs of Abuse and Heart Failure.

Journal of cardiac failure, 27(11), 1260-1275

View on PubMed ↗Publisher’s paper ↗

Citation

Grubb, Alex F; Greene, Stephen J; Fudim, Marat; Dewald, Tracy; Mentz, Robert J. (2021). Drugs of Abuse and Heart Failure.. Journal of cardiac failure, 27(11), 1260-1275. https://doi.org/10.1016/j.cardfail.2021.05.023