Exploratory Pilot Randomized Crossover Study of Transcutaneous Vagus Nerve Stimulation on Sleep Quality and Mood in Healthy Adults

Background: Transcutaneous vagus nerve stimulation (tcVNS) has been reported to influence autonomic regulation and sleep in various clinical settings.However, evidence in healthy populations is limited.This study investigated the effects of tcVNS on subjective sleep quality, mood, and autonomic function in healthy adults.Methods: We conducted a randomized, double-blind, crossover trial in which 29 healthy participants underwent two four-week stimulation phases (Active and Sham).Active stimulation was delivered at subthreshold intensity, whereas Sham stimulation involved identical device use without electrical current.Outcomes included the Pittsburgh Sleep Quality Index-Korean version (PSQI-K), Beck Depression Inventory-II (BDI-II), Hamilton Depression Rating Scale (HAM-D), and daily heart rate variability (HRV) indices collected using a validated smartphone-based application.Linear mixed-effects models were used to analyze questionnaire scores.Results: PSQI-K scores showed a statistically significant but modest reduction during Active stimulation compared with Baseline (P = 0.013) and Sham (corrected P < 0.001), although the mean change did not exceed the minimal clinically important difference.No significant changes were observed for BDI-II or HAM-D.HRV responses were heterogeneous across participants, with no significant group-level differences.No serious adverse events occurred, and mild transient ear discomfort or tingling was reported by 3 participants (10.3%) during Active stimulation.Conclusion: This exploratory pilot trial suggests that tcVNS was safe and well tolerated and may produce modest changes in subjective sleep quality in healthy adults.The absence of mood effects likely reflects low baseline symptom burden.These findings provide preliminary, hypothesis-generating evidence that stimulation parameters may warrant further investigation, and confirmation in adequately powered trials and clinical populations is required.