Physiological signals conveyed by the vagus nerve may generate quiescent psychological states conducive to contemplative practices. This suggests that vagal neurostimulation could interact with contemplative psychotherapies (e.g. mindfulness and compassion-based interventions) to augment their efficacy.

In a fully factorial experimental trial, healthy adults (n = 120) were randomized to transcutaneous vagus nerve stimulation (tVNS) plus Self-Compassion-Mental-Imagery Training (SC-MIT) or alternative factorial combinations of stimulation (tVNS or sham) plus mental imagery training (MIT: SC-MIT or Control-MIT). Primary outcomes were self-reported state self-compassion, self-criticism, and heart rate variability (HRV). Exploratory outcomes included state mindfulness and oculomotor attentional bias to compassion-expressing faces. Most outcomes were assessed acutely on session 1 at the pre-stimulation (T1), peri-stimulation (T2), and post-MIT + stimulation (T3) timepoints, and after daily stimulation+MIT sessions (eight sessions).

During session 1, a significant Timepoint × Stimulation × MIT interaction (p = 0.025) was observed, reflecting a larger acute T1→T3 increase in state self-compassion after tVNS+SC-MIT, with similar rapid effects on state mindfulness. Additionally, significant Session × MIT and Session × Stimulation interactions (p ≤ 0.027) on state mindfulness (but not self-compassion) suggested that tVNS+SC-MIT’s effects may accumulate across sessions for some outcomes. By contrast, changes in state self-criticism and compassion-related attentional bias were only moderated by MIT (not stimulation) condition. HRV was unaffected by stimulation or MIT condition.

tVNS augmented the effects of SC-MIT and might, therefore, be a useful strategy for enhancing meditation-based psychotherapies. Our findings also highlight the value of oculomotor attentional metrics as responsive markers of self-compassion training and the continued need for sensitive indices of successful vagal stimulation.

Transcutaneous vagus nerve stimulation (tVNS) is a promising therapeutic option for major depressive disorder (MDD) in adults. Alternative third-line treatments for MDD in adolescents are scarce. Here we aimed to assess the effects of acute tVNS on emotion recognition in adolescents with MDD.

Adolescents (14–17 years) with MDD (n = 33) and non-depressed controls (n = 30) received tVNS or sham-stimulation in a cross-sectional, case–control, within-subject cross-randomized controlled trial, while performing different tasks assessing emotion recognition. Correct responses, response times, and errors of omission and commission on three different computerized emotion recognition tasks were assessed as main outcomes. Simultaneous recordings of electrocardiography and electro dermal activity, as well as sampling of saliva for the determination of α-amylase, were used to quantify the effects on autonomic nervous system function.

tVNS had no effect on the recognition of gradually or static expressed emotions but altered response inhibition on the emotional Go/NoGo-task. Specifically, tVNS increased the likelihood of omitting a response toward sad target-stimuli in adolescents with MDD, while decreasing errors (independent of the target emotion) in controls. Effects of acute tVNS on autonomic nervous system function were found in non-depressed controls only.

Acute tVNS alters the recognition of briefly presented facial expressions of negative valence in adolescents with MDD while generally increasing emotion recognition in controls. tVNS seems to specifically alter early visual processing of stimuli of negative emotional valence in MDD. These findings suggest a potential therapeutic benefit of tVNS in adolescent MDD that requires further evaluation within clinical trials.