Vagus Nerve Stimulation Devices for Somatic Symptom Disorder

Study start date: November 17, 2025

Inclusion Criteria: 1. Meets the diagnostic criteria for Somatic Symptom Disorder (SSD) according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), as determined by a diagnostic interview with a board-certified psychiatrist. 2. The participant must be receiving stable, routine medical care throughout the trial period. 3. No adjustments to psychiatric or cardiovascular medications for at least one week prior to the start of the study. Exclusion Criteria: 1. Age below 18 or above 65 years. 2. Presence of psychotic symptoms, such as in comorbid schizophrenia. 3. Significant cognitive impairment (e.g., diagnosed dementia or intellectual disability) or difficulty completing the study questionnaires. 4. History of cervical vagotomy. 5. Presence of severe cardiovascular diseases, including: clinically significant tachycardia (resting heart rate \>100 bpm) or bradycardia (resting heart rate \<60 bpm); clinically significant hypertension (systolic \>160 mmHg or diastolic \>100 mmHg) or hypotension (blood pressure \<90/60 mmHg or mean arterial pressure \<65 mmHg); severe coronary artery disease; carotid atherosclerosis or stenosis; aneurysm; congestive heart failure; severe cardiac arrhythmias (e.g., prolonged QT interval, second- or third-degree atrioventricular block, atrial fibrillation, atrial flutter, recent ventricular tachycardia or fibrillation, clinically significant premature ventricular contractions); or myocardial infarction within the last five years. 6. Presence of severe neurological conditions, including severe head trauma, history of epilepsy, brain tumor, or cerebral hemorrhage. 7. Current diagnosis of cancer. 8. Presence of any active implanted medical devices (e.g., cochlear implant, ventricular shunt, implantable vagus nerve stimulator, pacemaker) or non-active implants that may interact with the nervous system (e.g., metal stents, bone plates, screws). 9. Anatomical abnormalities in the neck. 10. Currently pregnant. 11. Wearing jewelry near the tragus that cannot be removed before using the tVNS device. 12. Severe skin disease at the stimulation sites. 13. Known allergy to conductive gel materials. 14. Any other major medical condition that, in the investigator's judgment, could potentially affect the safety or efficacy of vagus nerve stimulation.