Transcutaneous vagus nerve stimulation (tVNS) to acutely reduce emotional vulnerability and improve emotional regulation in borderline personality disorder (tVNS-BPD): study protocol for a randomized, single-blind, sham-controlled trial

Abstract

Abstract Background: Borderline personality disorder (BPD) is considered a disorder of emotion regulation resulting from the expression of a biologically determined emotional vulnerability (that is, heightened sensitivity to emotion, increased emotional intensity/reactivity and a slow return to emotional baseline) combined with exposure to invalidating environments. Vagal tone has been associated with activity in cortical regions involved in emotion regulation and a lower resting state of vagal tone has been observed in BPD patients relative to healthy controls. Non-invasive transcutaneous vagus nerve stimulation (tVNS) has shown to reduce temper outbursts in adults with Prader-Willi Syndrome, to enhance recognition of emotions in healthy students and to improve depressive and anxiety symptoms. Furthermore, a single session of tVNS has been shown to acutely alter the recognition of facial expressions of negative valence in adolescents with MDD and increase emotion recognition in controls. However, the effect of tVNS on emotional vulnerability and regulation in individuals diagnosed with BPD has not been investigated. Our aims are to determine if tVNS is effective in acutely reducing emotional vulnerability and improve emotional regulation in BPD patients. Methods: 42 patients will be randomized to a single session of tVNS or sham-tVNS while going through an affect induction procedure. It will consist of the presentation of one neutral and three negative affect-evoking 4-minutes-long videos in sequence, each of which is followed by a 4-minutes post-induction period during which participants will rate the quality and intensity of their current self-reported emotions (post-induction ratings) and the perceived effectiveness in managing their emotions during the video presentation. The rating of the current self-reported emotions will be repeated after every post-induction period (recovery ratings). Mixed models with individuals as random effect will be used to investigate the ratings at each stage of the study, taking into account the repeated measures of same individuals at baseline, pre-induction, post-induction and recovery). Discussion: The study has potential to yield new insights into the role of vagal tone in emotion dysregulation in BPD and offer preliminary data on the effectiveness of tVNS as a possible non-invasive brain stimulation to treat a core symptom of BPD Trial registration: ClinicalTrials.gov NCT05892900. Retrospectively registered on Jun 07, 2023. https://clinicaltrials.gov/show/NCT05892900.