Effect of transcutaneous auricular vagus nerve stimulation on autonomic function in patients with generalized anxiety disorder: An assessor-participant blinded, randomized sham-controlled trial

INTERVENTION: Active taVNS Group:1.Stimulation Site: Cavum conchae and triangular fossa of the auricle , the core distribution area of the auricular branch of the vagus nerve (ABVN) . 2.Core Stimulation Parameters: Transcutaneous auricular vagus nerve stimulation device TENS‐200A (Suzhou Medical Devices Co., Ltd.). Stimulation was delivered in an alternating pattern: 20 Hz for 7 s and 4 Hz for 3 s; pulse width 0.2 ms. Stimulation intensity was set to the maximum tingling sensation tolerable by the subject, without sharp pain. 3.Intervention Duration and Frequency: Stimulation was applied alternately to both ears, 20 minutes per session, 3 times daily, for 4 consecutive weeks (28 days), totaling 168 stimulation sessions. ;Sham taVNS Group :1.Stimulation Site: Tragus of the auricle, an area without distribution of the auricular branch of the vagus nerve. 2.Stimulation Parameters and Intervention Protocol: The device appearance, operation interface, stimulation duration, daily intervention frequency, and total intervention period were identical to those in the experimental group. Only an extremely low‐intensity instantaneous electrical signal was delivered, producing a mild cutaneous sensation without effective vagus nerve stimulation. 3.Operator Training and Quality Control Requirements: Consistent with those of the experimental group to ensure the validity of blinding.; CONDITION: Generalized Anxiety Disorder PRIMARY OUTCOME: Hamilton Anxiety Scale‐14; SECONDARY OUTCOME: Time‐domain indices of heart rate variability;Frequency domain indices of heart rate variability;Pittsburgh sleep quality index;Zung self‐Rating Anxiety Scale;Zung Self‐Rating Depression Scale;Beck Scale for Suicide Ideation;HbO2;Hb; INCLUSION CRITERIA: 1. Aged 18 to 65 years, regardless of gender; m 2. Meeting the diagnostic criteria for generalized anxiety disorder as specified in the *Diagnostic and Statistical Manual of Mental Disorders (5th Edition)* (DSM‐5); 3. Having a baseline total score of >=14 on the Hamilton Anxiety Rating Scale (HAMA‐14), indicating moderate to severe anxiety symptoms; 4. For participants receiving medication: maintaining a stable dosage of anxiolytic/antidepressant medications within 4 weeks prior to enrollment, and committing not to adjust the medication regimen during the study period; 5. For medication‐free participants: having not used any anxiolytic, antidepressant, sedative or hypnotic drugs within 4 weeks prior to enrollment; 6. Right‐handed, having no contraindications for fNIRS examination, and being able to cooperate in completing cranial fNIRS and HRV examinations; 7. Fully understanding the study procedures, voluntarily signing a written informed con