Humming stimulates vagus nerve and nitric oxide production, linking to cardio-respiratory homeostasis in infants and mothers

Maintaining homeostasis and allostasis is fundamental for autonomic regulation, ensuring bodily states remain within optimal ranges. These processes involve reactive adjustments and predictive adaptations to environmental fluctuations, with social interactions playing a critical role. Humming, a unique vocalization, is intimately connected with cardio-respiratory processes and autonomic regulation, suggesting a potential mechanism for influencing internal states and promoting well-being, particularly in caregiving contexts.

This conceptual review synthesizes existing literature on the physiological and psychological effects of humming, drawing insights from infant-mother interactions, meditative practices, and caregiving contexts. The authors explore how humming, characterized by continuous gliding pitch and closed-mouth vocalization, influences cardio-respiratory processes and autonomic regulation by examining its unique vibratory propagation and connection to internal physiological states.

Humming, distinct from speech or singing, involves continuous vocal fold vibration and high resonance, propagating through the vocal tract, thorax, and spinal cord. This unique vocal production results in vagus nerve stimulation and the production of nitric oxide in the paranasal sinuses. The authors highlight that humming is organized around long sound-forming exhalations with slower air intake, directly linking it to cardio-respiratory processes and autonomic regulation. They propose that these physiological effects contribute to homeostasis and allostatic processes, which involve both reactive adjustments and predictive adaptations to environmental changes, particularly within social contexts like mother-infant interactions.