24-Hour Heart Rate Variability Level Differences between Individuals Living with and without Cannabis Use Disorder

Technical Summary: 24-Hour Heart Rate Variability Level Differences between Individuals Living with and without Cannabis Use Disorder

Problem Statement
Despite the rising prevalence of cannabis use, particularly among young adults, the physiological impact of chronic, disordered cannabis use on the cardiovascular system remains under-explored. Existing literature regarding Heart Rate Variability (HRV)—a non-invasive index of autonomic nervous system function and parasympathetic activity—is limited by heterogeneous definitions of cannabis use, inadequate control for confounding substances (such as alcohol and tobacco), and a reliance on short-duration baseline measurements rather than continuous monitoring. Furthermore, previous studies have yielded mixed results, with some suggesting increased HRV in cannabis users and others indicating decreased HRV. There is a critical gap in understanding how individuals meeting the diagnostic criteria for Cannabis Use Disorder (CUD) differ from non-using controls in terms of 24-hour autonomic regulation.

Methodology
This cross-sectional study examined 84 Black/African American undergraduate students (mean age = 19.59 years; 72% female) recruited from a historically Black university in central Virginia. Participants were classified into two groups using the Mini International Neuropsychiatric Interview (MINI):

• CUD Group (n = 35): Met DSM-5 criteria for Cannabis Use Disorder.
• Control Group (n = 49): No lifetime cannabis use and no other substance use disorders in the past 12 months.

Data Collection and Measures:

• HRV Monitoring: Participants wore Garmin Venu 3 smartwatches continuously for three days to capture 24-hour HRV data. Metrics included time-domain indices (Root Mean Square of Successive Differences [RMSSD]) and frequency-domain indices (Low Frequency [LF], High Frequency [HF], and LF/HF ratio). The study utilized photoplethysmography (PPG) derived metrics, noting modest correspondence with ECG-derived measurements in supplemental analyses.
• Covariates: The study controlled for demographics (age, sex, employment), psychological distress (Brief Symptom Inventory-18), body mass index (BMI), and substance use risk scores for tobacco and alcohol (Alcohol, Smoking, and Substance Involvement Screening Test [ASSIST]).
• Analysis: Analysis of Covariance (ANCOVA) with Bonferroni corrections was employed to compare HRV metrics between groups, adjusting for statistically significant covariates (specifically tobacco and alcohol risk scores).

Key Results

• Demographics and Baseline: The CUD and control groups did not differ significantly in age, sex, employment status, psychological distress scores, or BMI.
• Substance Use: As expected, the CUD group reported significantly higher risk scores for both tobacco and alcohol use compared to controls.
• Heart Rate: The CUD group exhibited a higher mean resting heart rate (88.28 bpm) compared to controls (83.63 bpm), though this difference did not reach statistical significance (p = 0.068).
• HRV Metrics:
  • Time Domain: The CUD group showed a trend toward lower RMSSD (p = 0.051) in raw comparisons.
  • Frequency Domain: The CUD group exhibited significantly lower LF HRV (p = 0.02) and HF HRV (p = 0.02) compared to controls.
  • Adjusted Analysis: After controlling for tobacco and alcohol covariates, the differences remained statistically significant. Individuals with CUD had significantly lower RMSSD (p = 0.018), HF HRV (p = 0.017), and LF HRV (p = 0.04) than controls. The LF/HF ratio did not differ significantly between groups.

Key Contributions
This study provides the first examination of 24-hour HRV differences specifically between individuals diagnosed with CUD and a demographically matched control group with no history of problematic cannabis use. Unlike prior research that relied on brief, static measurements or urine drug testing without diagnostic confirmation, this study utilized continuous 24-hour monitoring and rigorous diagnostic criteria (MINI). Additionally, the study explicitly controlled for the confounding effects of concurrent tobacco and alcohol use, isolating the association between CUD and autonomic dysregulation.

Significance and Claims
The authors claim that individuals living with CUD exhibit significantly lower 24-hour HRV, indicating reduced parasympathetic activity and autonomic inflexibility. This finding aligns with the Neurovisceral Integration Theoretical framework, suggesting that CUD is characterized not only by psychological dysregulation but also by measurable physiological constraints in adapting to environmental demands.

The paper posits that autonomic dysregulation may serve as a modifiable risk marker and a potential treatment target for CUD. By identifying reduced HRV as a consequence or correlate of chronic cannabis use disorder, the study suggests that interventions targeting autonomic regulation, such as HRV biofeedback, could support recovery and improve emotion regulation in this population. The authors conclude that these findings highlight the need to consider cardiovascular autonomic health in the assessment and treatment of cannabis use disorders.