tVNS and Approach-Avoidance Behavior in Anhedonia and Anxiety

This study investigates if anhedonia and anxiety symptoms are associated with alterations in reinforcement learning, effort trade-offs for wins vs. punishments, and foraging behavior under threat. Moreover, it will investigate whether these processes can be influenced by a metabolic load and/or transcutaneous vagus nerve stimulation (tVNS). The project consists of (a) an online reinforcement learning study, used to characterize learning, reward sensitivity, and meta-cognition, and (b) a laboratory study in which participants first undergo fMRI while completing an effort-based decision-making task. Second, participants will complete two sessions in VR with randomized active or sham tVNS during a foraging task before and after a caloric load with concurrent physiological recordings.

NCT Number	NCT07476469
Lead Sponsor	Dr. Nils B. Kroemer Collaborators: University of Bonn, Else Kröner Fresenius Foundation
Conditions	Healthy Participants, Anxiety Disorders (With High Anxiety Symptoms), Depressive Disorders (With High Anhedonia Symptoms), Comorbid Depression and Anxiety Disorder (With High Anhedonia and High Anxiety Symptoms)
Enrollment	104 participants
Start Date	2026-03-23
Primary Completion	2027-12-31 (estimated)
Study Completion	2028-12-31 (estimated)
Updated on ClinicalTrials.gov	2026-04-23