STRESS, THE HPA AXIS & AYURVEDA: PHYSIOLOGY OF PRĀṆĀYĀMA, RASĀYANA & VĀTA REGULATION

Stress is a multidimensional biological response with well-defined neuroendocrine mechanisms centred on the hypothalamic–pituitary–adrenal (HPA) axis. Chronic dysregulation of the HPA axis contributes to cardiometa-bolic disease, mood disturbance and impaired immune function. Classical Ayurveda conceptualises stress and arousal through dosha imbalance — principally Vāta — and prescribes behavioural (Prāṇāyāma), dietary, and pharmacologic (Rasāyana) interventions to restore homeostasis. This review synthesises contemporary research linking HPA physiology with Ayurvedic concepts and critically appraises mechanisms by which Prāṇāyāma and Rasāyana may modulate stress responses. Evidence indicates that controlled, slow breathing increases vagal afferent activity, improves heart rate variabil-ity (HRV), and lowers sympathetic arousal, thereby attenuating HPA activation. Parallel clinical and mechanistic research on key Rasāyana botanicals (e.g., Withania somnifera, Tinospora cordifolia, Bacopa monnieri, Embli-ca officinalis), which exhibit adaptogenic, anti-inflammatory and HPA-modulating effects in animal models and human trials. Recent Ayurgenomics and prakriti research reveal genotype–phenotype correlations that may ex-plain interindividual variability in stress resilience and HPA reactivity. We propose an integrative model in which Prāṇāyāma restores autonomic balance via vagal mechanisms, while Rasāyana exerts endocrine, immunologic, and molecular buffering of HPA axis output; together, these address both immediate neurophysiological arousal and longer-term resilience. Finally, we identify methodological gaps — including heterogeneity in intervention protocols, small sample sizes, and limited mechanistic human studies — and propose a roadmap for translational research that combines physiological endpoints (cortisol dynamics, HRV, inflammatory biomarkers) with standardised Ayurvedic phenotyping. This synthesis supports a physiolog-ically grounded framework for investigating Ayurvedic approaches to stress management and HPA-axis modula-tion.