Heart Rate Variability Drops Immediately After Cannabis Smoking in Young Adults with CUD | Research

The takeaway

African American young adults with cannabis use disorder showed significant decreases in heart rate variability and increases in heart rate immediately after smoking cannabis, indicating reduced parasympathetic activity.

Cannabis users concerned about heart health, cardiovascular researchers, addiction specialists

HRV significantly decreased after each cannabis smoking session

What the researchers found

In 31 young adults with CUD wearing Garmin smartwatches for 3 days, both time-domain and frequency-domain HRV metrics were significantly lower after cannabis smoking compared to before, with a corresponding increase in average heart rate.

Why it matters

Cannabis is often perceived as relaxing, but this study shows it acutely reduces parasympathetic nervous system activity in habitual users. For people with cannabis use disorder, repeated suppression of heart rate variability could have cardiovascular implications over time.

The numbers in context

31 participants; 84% women; mean age 19.7 years; significant decreases in both time and frequency domain HRV after smoking; significant increase in heart rate.

How the study worked

Observational study of 31 African American undergraduates (84% women, mean age 19.7) meeting criteria for CUD via the MINI interview. Participants wore Garmin smartwatches for 3 consecutive days and reported cannabis smoking sessions via survey. HRV was measured via photoplethysmography.

What this study cannot tell us

Small sample (n = 31) predominantly female. Consumer-grade smartwatch HRV measurement is less precise than clinical ECG. Self-reported smoking times may be inaccurate. No control for concurrent tobacco or other substance use.

How to read the evidence

Small observational study using consumer-grade wearable devices without a control group.

When this study was published

2025 publication

The bigger picture

Low heart rate variability is associated with increased cardiovascular risk, poorer stress adaptation, and worse health outcomes. If cannabis chronically suppresses parasympathetic function in heavy users, this adds to a growing body of evidence about cardiovascular effects of regular cannabis use.

Questions still open

Does chronic cannabis use lead to persistent reductions in baseline HRV?
Are these acute cardiovascular effects different across consumption methods (smoking vs. edibles vs. vaping)?

Common questions

Does cannabis affect heart rate variability?

In this study of young adults with cannabis use disorder, HRV (a measure of parasympathetic nervous system activity) dropped significantly immediately after smoking cannabis, while heart rate increased. Lower HRV is generally associated with poorer cardiovascular health.

Is smoking cannabis bad for your heart?

This study found cannabis smoking acutely reduces parasympathetic nervous system function (measured by HRV) in habitual users. While the long-term cardiovascular implications are not yet clear, repeatedly suppressing HRV could be a concern over time.

Read the original research

Parasympathetic decreases immediately following self-reported cannabis smoking among adults living with cannabis use disorder.

International journal of psychophysiology : official journal of the International Organization of Psychophysiology, 214, 113211

View on PubMed ↗Publisher’s paper ↗

Citation

Keen, Larry; Kuno, Caroline Bena; Morris, Alexis. (2025). Parasympathetic decreases immediately following self-reported cannabis smoking among adults living with cannabis use disorder.. International journal of psychophysiology : official journal of the International Organization of Psychophysiology, 214, 113211. https://doi.org/10.1016/j.ijpsycho.2025.113211