Effects of transcutaneous vagus nerve stimulation on subthreshold affective symptoms and perceived stress: Findings from a single-blinded randomized trial in community-dwelling adults

Abstract

Transcutaneous vagus nerve stimulation (tVNS) lowers depression and anxiety in clinical populations, but its preventive utility in alleviating subthreshold depression and anxiety symptoms or perceived stress in the general population is uncertain. In this single-blinded randomized controlled trial 70 participants (28 men; M_age 49,33 years, 18–75 age range) were allocated to four groups: early active or sham tVNS and late active or sham tVNS to explore outcome changes between the preintervention and postintervention in active and sham groups, changes after active and sham stimulation ended in the early groups, or outcomes during waiting time in the late groups. Early intervention and sham groups received daily 4 h tVNS between Day 0 and 13, while late intervention and sham groups received tVNS between day 14 and 28. Active tVNS was delivered via transcutaneous electrical stimulation on the left tragus and sham tVNS was applied on the left earlobe. Affective symptoms and stress were measured with questionnaires. Effects of active tVNS stimulation were superior to sham stimulation in early phase groups, but not in late phase groups, for anxiety symptoms and perceived stress, with no superior effects of tVNS against sham detected for depressive symptoms. Our study tentatively indicates that tVNS application could be scaled-up to a population level to potentially mitigate stress vulnerability and higher anxiety, which are often prevalent in older adults and increased in the ageing process.