RecruitingNAINTERVENTIONAL

tVNS and Approach-Avoidance Behavior in Anhedonia and Anxiety

This research explores how people with anxiety, anhedonia (a reduced ability to feel pleasure), or both, react to things that might give them a reward versus things that might cause harm. We want to see if anhedonia and anxiety change how people learn and make decisions, especially when under threat. The study also investigates whether a gentle electrical stimulation called transcutaneous vagus nerve stimulation (tVNS) can influence these reactions. Participants will complete online tasks, have brain scans (fMRI), and play virtual reality games. We are particularly interested in how the body’s signals, like after eating, might change how tVNS works. The aim is to find better ways to help people with mood and anxiety issues.

At a glance

Status

Recruiting

Phase

Sponsor

Dr. Nils B. Kroemer

Enrolment target

104

Start

23 Mar 2026

Estimated completion

31 Dec 2028

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)

What is this study about?

This study aims to understand how conditions like anxiety and anhedonia (a feeling where you can't experience pleasure from things you used to enjoy) affect our brain's natural response to rewards and threats. For example, do people with these conditions react differently when faced with a chance to gain something positive compared to a potential danger? We also want to explore whether a gentle, non-invasive treatment called transcutaneous vagus nerve stimulation (tVNS) can help to balance these responses.

tVNS works by delivering a mild electrical pulse to a nerve in your neck, which connects to your brain and different parts of your body. The idea is that stimulating this nerve might influence how your brain processes emotions and makes decisions. The study will look at various things, including how you learn from experiences, how much effort you're willing to put in for a reward versus avoiding punishment, and how you behave when trying to find resources in a virtual world where there might be threats.

We're also interested in how your body's energy levels, like after you've eaten a meal, might affect these processes and how tVNS works. By understanding these connections better, we hope to discover new and more effective ways to help people manage anxiety and anhedonia, ultimately improving their emotional well-being.

Key takeaways

This study explores how anxiety and anhedonia affect decision-making.
It investigates if gentle nerve stimulation (tVNS) can influence these behaviours.
Participation involves online tasks, brain scans, and virtual reality games.
You'll experience both active and inactive (sham) stimulation.
The study looks at how your eating state might impact the effects.
The goal is to find better ways to help people with mood and anxiety problems.

Who may be eligible?

To join this study, you need to be generally healthy, or have symptoms of anxiety, anhedonia (a reduced ability to feel pleasure), or both. You should be between 18 and 40 years old and have a body mass index (BMI) between 18.5 and 30. You also need to be able to fully understand and agree to take part in the study.

There are certain conditions that would prevent you from joining. These include having a high risk of suicide, or a history of severe neurological problems (like ADHD, schizophrenia, bipolar disorder), severe substance abuse, PTSD, OCD, diabetes, epilepsy, or serious heart disease. If you've had an eating disorder or certain body-focused symptoms in the last year, you also wouldn't be able to participate. You shouldn't be pregnant or breastfeeding if you are female.

Additionally, you can't take part if you have metal implants or severe claustrophobia that would prevent you from having an MRI scan. Your vision, hearing, and movement must be good enough for the tasks. If you wear hearing aids or have skin problems on your right ear, you might not be able to have the tVNS treatment.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you between 18 and 40 years old?
Is your BMI (body mass index) between 18.5 and 30?
Do you have good vision, hearing, and movement?
Have you *not* had severe neurological conditions, diabetes, epilepsy, or serious heart problems?
Are you *not* pregnant or breastfeeding?
Are you able to have an MRI scan (no metal implants, not severely claustrophobic)?

Answer every question to see your result.

What does participation involve?

If you join this study, you'll first go through an online screening to check if you're suitable. This will involve filling out questionnaires about your mood and anxiety, and completing an online learning task over about two weeks.

Next, you'll have a diagnostic visit and medical assessment, which includes an MRI scan of your brain. After this, you'll take part in laboratory sessions. These involve completing an effort-based decision-making task while having a brain scan, and then two virtual reality (VR) sessions. During the VR tasks, you’ll receive either active tVNS (gentle electrical stimulation) or a sham (inactive) stimulation.

Crucially, you'll do one VR session when you haven't eaten for at least 4 hours (hungry state) and another after drinking a standardised milkshake (post-meal state). You'll be able to move freely during the VR tasks, and we'll record your body's reactions, like your heart rate. This is a crossover study, meaning you'll get both active and sham stimulation at different times. The total duration of your participation will depend on how quickly you complete the various stages, but it involves several visits and online tasks.

Potential risks and benefits

Participating in this study might help researchers understand anxiety and anhedonia better, which could lead to improved treatments in the future. You will not receive any direct medical benefit from taking part, and we are not giving medical advice. Potential risks are generally mild and may include discomfort from the tVNS (like a tingling sensation on the ear) or from the MRI scan (noise, feeling confined). Some people might find the tasks challenging or experience minor fatigue. You are free to withdraw from the study at any time, for any reason, without it affecting your medical care.

Locations (1)

University Hospital Bonn, Bonn, Germany
Verified postcode
Bonn, Germany· Recruiting

Common questions

What is tVNS?

tVNS stands for 'transcutaneous vagus nerve stimulation.' It's a gentle, non-invasive treatment that uses a small electrical current to stimulate a nerve in your ear, which then sends signals to your brain.

What is anhedonia?

Anhedonia is when you have a reduced ability to feel pleasure or joy from things you used to enjoy, like hobbies, food, or spending time with loved ones.

Will I get the actual tVNS treatment?

Yes, you will receive both the active tVNS and a 'sham' (inactive) stimulation at different times during the study. This helps researchers compare the effects accurately.

What is a 'foraging task under threat'?

It's a virtual reality game where you might search for items or resources while also encountering things that could be a threat, forcing you to make decisions about approach or avoidance.

Do I have to do all the parts of the study?

Yes, to ensure the research is complete and valid, it's expected that you participate in all parts of the study once you've agreed to join.

How to find out more

Dr. Anne Kühnel

akuehnel@uni-bonn.de +49 228 28711519 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.