Low-Intensity Unfocused Ultrasound Vagus Nerve Stimulation to Increase Heart Rate Variability and Reduce Anxiety

Anxiety disorders are among the most common mental health concerns in the United States, yet current treatments are often time-consuming, costly, or ineffective. Electrical vagus nerve stimulation has been approved as a treatment for epilepsy and depression, and some studies show it has reduced anxiety as well, but there are limitations to electrical stimulation. It isn’t widely accessible and can have side effects such as neck pain, dizziness, headache, nasopharyngitis, and oropharyngeal pain (Farmer et al., 2021). Ultrasound stimulation of the vagus nerve could develop as a fast-acting, easily accessible, and safer treatment for anxiety. In this study, we tested whether low-intensity unfocused ultrasound stimulation could modulate heart rate variability and anxiety scores in a healthy group of participants. There were three between-subjects conditions: two minutes of interval simulation (30s on, 30s off), no-interval simulation (continuous), and placebo. Participants were split into anxious and non-anxious subgroups based on scores on the Spielberger State-Trait Anxiety Inventory. Results for the group as a whole showed no significant change in heart rate variability or anxiety scores. However, when participants were split into anxious and non-anxious subgroups, the anxiety scores were significantly reduced relative to the placebo group in the Interval condition for the anxious participants only. These results, while preliminary, suggest that low-intensity unfocused ultrasound stimulation of the vagus nerve could be a treatment for anxiety. Future studies should focus on anxious people and study the mechanism of the reduced anxiety in more depth to confirm these results.