A Review of Vagus Nerve Stimulation for Disease: Comprehensive Theory and Evidence for Mechanisms of Action.

Vagus nerve stimulation (VNS) is an established neuromodulatory therapy approved for epilepsy, depression, obesity, stroke rehabilitation, rheumatoid arthritis, migraine, and cluster headaches. Its therapeutic potential has expanded dramatically, with growing evidence supporting its efficacy across a wide spectrum of neurological, psychiatric, cardiovascular, immunological, metabolic, and gastrointestinal disorders. Despite this progress, the field has lacked a comprehensive synthesis that unifies mechanistic insights with translational applications across organ systems. This review addresses that gap by systematically integrating current knowledge in the multifactorial mechanisms through which VNS modulates central and peripheral functions, including neuromodulator release, synaptic plasticity, autonomic regulation, neuroimmune control, and endocrine integration. In addition, this review identifies key limitations of VNS, including biological heterogeneity, technical constraints, and methodological variability, and proposes future innovations such as selective fiber targeting, closed-loop systems, and artificial intelligence-guided personalization. By providing a rigorous, system-level overview of VNS mechanisms and their translational relevance, this article serves as a foundational resource for advancing the science and clinical deployment and helping illustrate future directions for precision neuromodulation and bioelectronic medicine.