RecruitingNot Applicable

tVNS and Approach-Avoidance Behavior in Anhedonia and Anxiety

Germany104 participantsStarted 2026-03-23

Plain-language summary

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.

Who can participate

Age range

18 Years – 40 Years

Sex

ALL

See this in plain English?

AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.

Inclusion Criteria: * BMI between 18,5 and 30,0 kg/m2, * between 18 and 40 years of age, and * be able and willing to provide informed consent. Exclusion Criteria: * have a high risk of suicide, * have a lifetime diagnosis of severe neurological disorder (incl. ADHD), schizophrenia, bipolar disorder, or severe substance abuse, posttraumatic stress disorder, obsessive-compulsive disorder, diabetes, epilepsy, or coronary heart disease * have fulfilled criteria for an eating disorder or somatic symptom disorder within the last 12-months, * take medication (except psychopharmacological medication for MDD or anxiety), patients have to be on stable psychopharmacological medication for at least two months before study participation (minimizing confounding effects) * contraindications for MRI (metal implants or claustrophobia) * for female individuals if they are pregnant or nursing at the time, * impaired movement ability or hearing * impaired, uncorrected vision (need contact lenses) * contraindications for tVNS hearing aids or diseased skin on the right ear.

Questions worth asking your doctor

Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.

1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?

Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.

Questions for the trial coordinator

The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.

1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?

A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.

What they're measuring

Stimulation-induced changes in the number of rewards collected under threat (VR foraging task)

Timeframe: During each stimulation session (tVNS and sham) throughout study completion (approximately 3 weeks)

BOLD response during the effort-trade-off task (offer-phase)

Timeframe: Collected during fMRI session (single session throughout study completion ~35min per participant)

Reward learning

Timeframe: Online task performance assessed online before lab-visits (approximately 10 days)

Metabolic state x stimulation-induced changes in the number of rewards collected under threat (VR task)

Timeframe: During each stimulation session (tVNS and sham) throughout study completion (approximately 3 weeks)

Trial details

NCT IDNCT07476469

SponsorDr. Nils B. Kroemer

Sponsor typeOTHER

Study typeINTERVENTIONAL

Primary completion2027-12-31

Contact for this trial

Dr. Anne Kühnel

+49 228 28711519 akuehnel@uni-bonn.de

View on ClinicalTrials.gov More Healthy Participants trials

Plain-language summary

Who can participate

Age range

18 Years – 40 Years

Sex

ALL

See this in plain English?

AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.

What they're measuring

Stimulation-induced changes in the number of rewards collected under threat (VR foraging task)

Timeframe: During each stimulation session (tVNS and sham) throughout study completion (approximately 3 weeks)

BOLD response during the effort-trade-off task (offer-phase)

Timeframe: Collected during fMRI session (single session throughout study completion ~35min per participant)

Reward learning

Timeframe: Online task performance assessed online before lab-visits (approximately 10 days)

Metabolic state x stimulation-induced changes in the number of rewards collected under threat (VR task)

Timeframe: During each stimulation session (tVNS and sham) throughout study completion (approximately 3 weeks)