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

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.

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.

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.

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.

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.