Cardiovagal Tone in Generalised Anxiety Disorder: A Case Control Study

Introduction Generalised anxiety disorder (GAD) is a prevalent psychiatric condition increasingly associated with autonomic nervous system dysfunction. Specifically, impaired cardiovagal tone, a marker of reduced parasympathetic modulation of cardiac function, has been linked to emotional dysregulation, behavioural rigidity, and elevated cardiovascular morbidity. The standard Ewing's battery of parasympathetic autonomic function tests provides a reproducible and non-invasive means of assessing such dysfunction. This study aimed to comprehensively evaluate cardiovagal tone in newly diagnosed, treatment-naive GAD patients using validated Ewing's tests. Methods In this cross-sectional case-control study, 40 GAD patients (aged 31 to 40 years) diagnosed per the Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 criteria were compared with 40 age- and sex-matched healthy controls. Cardiovagal tone was assessed using the standard Ewing's battery: heart rate response to deep breathing (HRDB), expiration:inspiration (E:I) ratio, Valsalva ratio, and the 30:15 ratio during the head-up tilt test (HUT). Results The GAD patients demonstrated significantly lower HRDB (21.61 ± 9.75 vs. 27.35 ± 9.64 beats/min, p = 0.009) and E:I ratio (1.29 ± 0.26 vs. 1.47 ± 0.20, p = 0.001) compared to controls, indicating reduced parasympathetic (vagal) activity. The Valsalva ratio (p = 0.410) and 30:15 ratio (p = 0.664) showed no statistically significant differences. These findings underscore the presence of early, subclinical autonomic imbalance in GAD, particularly affecting the cardiovagal domain. Conclusion Treatment-naive GAD patients exhibit significant cardiovagal dysfunction, as reflected by reduced heart rate variability and E:I ratio. Impaired cardiovagal tone is an independent risk factor for adverse cardiovascular outcomes and may serve as a physiological marker of early brain-heart axis disruption. Routine application of Ewing's parasympathetic test battery may assist in cardiovascular risk stratification and guide holistic neurocardiac management in anxiety disorders.