NCT05441774

Brief Summary

This experimental proof-of-concept study in healthy volunteers investigates whether a specific form of self-relating, namely, self-compassion, can be controlled through non-invasive stimulation of the vagus nerve. The vagus nerve is part of the parasympathetic nervous system (the 'rest and digest' system) and its fibers are spread throughout the upper body, face, and neck, including a branch that innervates parts of the external ear (e.g. the tragus), close to the surface of the skin. This allows the 'auricular branch' of the vagus nerve to be readily stimulated electrically. Importantly, this can be achieved non-invasively using a transcutaneous vagus nerve stimulation (tVNS) device. The investigators will test the effects of tVNS alone and in combination with a meditation-like technique that is intended to increase participants' feelings of self-compassion (self-compassion imagery). In particular, the investigators will assess participants' experience of self-compassion and self-criticism, as well as other outcome measures, before and during stimulation, and again after they perform the self-compassionate imagery exercise. These effects will be compared to three other groups: one that receives tVNS along with a control (sham) imagery procedure, another that receives sham tVNS and self-compassion imagery, and a final group that receives sham tVNS and sham imagery. It is expected that the group that receives active tVNS and the self-compassion imagery exercise will experience the largest average increases in self-compassion and decreases in self-criticism. The findings of this study will help us better understand the role of the vagus nerve in complex cognitive-emotional experiences - like compassion - and may also motivate the development of bioelectronic stimulation methods that can be used alongside psychological techniques for improving self-compassion and reducing self-criticism, particularly among people with certain psychological disorders.

Trial Health

87
On Track

Trial Health Score

Automated assessment based on enrollment pace, timeline, and geographic reach

Enrollment
120

participants targeted

Target at P75+ for not_applicable healthy-volunteers

Timeline
Completed

Started Jun 2022

Geographic Reach
1 country

1 active site

Status
completed

Health score is calculated from publicly available data and should be used for screening purposes only.

Trial Relationships

Click on a node to explore related trials.

Study Timeline

Key milestones and dates

First Submitted

Initial submission to the registry

June 23, 2022

Completed
4 days until next milestone

Study Start

First participant enrolled

June 27, 2022

Completed
4 days until next milestone

First Posted

Study publicly available on registry

July 1, 2022

Completed
9 months until next milestone

Primary Completion

Last participant's last visit for primary outcome

March 15, 2023

Completed
Same day until next milestone

Study Completion

Last participant's last visit for all outcomes

March 15, 2023

Completed
Last Updated

May 23, 2023

Status Verified

May 1, 2023

Enrollment Period

9 months

First QC Date

June 23, 2022

Last Update Submit

May 22, 2023

Conditions

Healthy Volunteers

Keywords

Vagus nerveNeurostimulationTranscutaneous vagus nerve stimulationMental imageryCompassionMeditation

Outcome Measures

Primary Outcomes (3)

  • State self-compassion

    Self-compassion subscale of the scenario-based self-compassion and self-criticism Scales (SCCS; Falconer et al, 2015). Score range: 15 (minimum) to 105 (maximum). High scores indicate greater self-compassion (desirable outcome)

    1 week

  • Heart rate variability

    Root mean square of successive differences (commonly, RMSSD) between normal beats; high-frequency power. Higher levels indicate greater heart rate variability (a desirable outcome)

    1 week

  • State self-criticism

    Self-criticism subscale of the SCCS (Falconer et al, 2015). Score range: 15 (minimum) to 105 (maximum). High scores indicate greater self-criticism (undesirable outcome)

    1 week

Secondary Outcomes (4)

  • Eye-tracking attention metrics

    1 week

  • State mindfulness

    1 week

  • State positive and negative affect

    1 week

  • State positive affect (Safe/content)

    1 week

Study Arms (4)

Sham stimulation plus sham imagery

SHAM COMPARATOR

Double sham group: Stimulator electrodes will be applied to earlobe (sham stimulation); imagery task will involve a 'draw-a-face-in-imagination' (sham imagery) task.

Device: Sham transcutaneous vagus nerve stimulationBehavioral: Sham mental imagery

Active stimulation plus sham imagery

OTHER

Single (imagery) sham group: Stimulator electrodes will be applied to the tragus (active stimulation); 'draw-a-face-in-imagination' (sham imagery) task.

Device: Active transcutaneous vagus nerve stimulationBehavioral: Sham mental imagery

Sham stimulation plus active self-compassion imagery

OTHER

Single (stimulation) sham group: earlobe (sham) stimulation; imagery task will involve directing compassion to the self (self-compassion, active imagery).

Behavioral: Active self-compassion imageryDevice: Sham transcutaneous vagus nerve stimulation

Active stimulation plus active self-compassion imagery

ACTIVE COMPARATOR

Double active group: tragus (active) stimulation; self-compassion (active imagery)

Device: Active transcutaneous vagus nerve stimulationBehavioral: Active self-compassion imagery

Interventions

Active transcutaneous vagus nerve stimulationDEVICE

TVNS is a non-invasive counterpart to surgical methods for stimulating the vagus. For the active condition, stimulator electrodes deliver a mild electrical current to the tragus. Stimulation parameters: stimulation of left tragus via two gold-plated electrodes, attached by ear-clip. Waveform: rectangular, frequency: 20 Hz, pulse width: 0.2 ms, individually adjusted intensity based on participant's perceptual threshold.

Also known as: Parasym tVNS device
Active stimulation plus active self-compassion imageryActive stimulation plus sham imagery
Active self-compassion imageryBEHAVIORAL

Self-compassion imagery is both a meditative technique and a component of compassion-focused cognitive therapy. Here, self-compassionate imagery is delivered as standardized audio-recorded instructions.

Active stimulation plus active self-compassion imagerySham stimulation plus active self-compassion imagery
Sham transcutaneous vagus nerve stimulationDEVICE

TVNS is a non-invasive counterpart to surgical methods for stimulating the vagus. For the sham condition, stimulator electrodes deliver a mild electrical current to the earlobe. Stimulation parameters: stimulation of left earlobe via two gold-plated electrodes, attached by ear-clip. Waveform: rectangular, frequency: 20 Hz, pulse width: 0.2 ms, individually adjusted intensity based on participant's perceptual threshold.

Also known as: Parasym tVNS device
Sham stimulation plus active self-compassion imagerySham stimulation plus sham imagery
Sham mental imageryBEHAVIORAL

Draw-a-face-in-imagination is the sham/ control imagery condition. Here, control imagery instructions are delivered as a standardized audio-recording, well-matched to self-compassion imagery for number of words, complexity of language, and duration of the audio instructions.

Active stimulation plus sham imagerySham stimulation plus sham imagery

Eligibility Criteria

Age18 Years - 35 Years
Sexall
Healthy VolunteersYes
Age GroupsAdult (18-64)

You may qualify if:

  • Fluency in English
  • Good (including corrected) vision and hearing.

You may not qualify if:

  • Current use of any medication for a psychiatric condition
  • Regular use of any medication used to treat a cardiovascular condition or inflammation
  • Use of any illicit recreational drug \>2/week
  • Regularly consuming \>14 standard UK 'units' of alcohol
  • Currently receiving treatment for any mental health condition
  • Scores on screening measures of depression (PHQ-2) and/or anxiety (GAD-2) that indicate significant levels of current/recent anxiety or depression (scores on either \>4)
  • History of serious mental health problems (schizophrenia, bipolar disorder)
  • Past or current cardiovascular or neurological problems
  • Current/past problems related to chronic/recurring facial or ear pain
  • Skin irritation/ broken skin at stimulation site
  • Pregnancy or likelihood of becoming pregnant during study
  • Previous adverse response to meditation.

Contact the study team to confirm eligibility.

Sponsors & Collaborators

Study Sites (1)

Clinical Psychopharmacology Unit

London, WC1E 6BT, United Kingdom

Location

Related Publications (1)

  • Kamboj SK, Peniket M, Simeonov L. A bioelectronic route to compassion: Rationale and study protocol for combining transcutaneous vagus nerve stimulation (tVNS) with compassionate mental imagery. PLoS One. 2023 Mar 13;18(3):e0282861. doi: 10.1371/journal.pone.0282861. eCollection 2023.

    PMID: 36913378DERIVED

Study Officials

  • Sunjeev K Kamboj, PhD

    UCL

    PRINCIPAL INVESTIGATOR

Study Design

Study Type
interventional
Phase
not applicable
Allocation
RANDOMIZED
Masking
SINGLE
Who Masked
PARTICIPANT
Masking Details
Study design and aims will be concealed from participants. They will not be made aware of the presence of active versus sham conditions (all participants are given the expectation of active stimulation and imagery). Participants are informed of their imagery condition before consent is obtained on the first lab session. Study aims will be disclosed at debriefing, after all experimental procedures have been completed.
Purpose
BASIC SCIENCE
Intervention Model
FACTORIAL
Model Details: Factorial 2 (sham stimulation v active stimulation) x 2 (sham v self-compassion imagery)
Sponsor Type
OTHER
Responsible Party
SPONSOR

Study Record Dates

First Submitted

June 23, 2022

First Posted

July 1, 2022

Study Start

June 27, 2022

Primary Completion

March 15, 2023

Study Completion

March 15, 2023

Last Updated

May 23, 2023

Record last verified: 2023-05

Data Sharing

IPD Sharing
Will share

Data will be shared upon reasonable request to PI

Locations

GB(1)