Anxiety disorders are highly prevalent and carry significant personal and societal costs. Auricular transcutaneous vagus nerve stimulation (tVNS) is a non-invasive neuromodulation approach that targets vagal afferents to regulate autonomic tone and emotional responses.

In this longitudinal, randomised, controlled study (N=32, ages 18–31), participants with moderate to severe baseline anxiety received daily sessions of active tVNS or placebo stimulation for four weeks. Self-reported anxiety was measured using the Generalized Anxiety Disorder Scale (GAD-7) and the State-Trait Anxiety Inventory–State scale (STAI-S) at baseline, two weeks, and four weeks.

Active tVNS produced significant improvements. By week four, GAD-7 scores decreased by 47% (t(31)=7.92, p<0.001), representing a shift from severe to mild anxiety. STAI-S scores decreased by 14% (t(31)=2.85, p=0.008), reflecting a transition from high to moderate anxiety. Placebo recipients showed only modest early reductions that plateaued or rebounded by week 4.

These findings demonstrate that auricular tVNS provides sustained, longitudinal anxiolytic effects when administered daily, with meaningful improvements emerging as early as the two week mark and consolidating by four weeks.

Anxiety disorders affect nearly one third of adults during their lifetime. There is growing interest in neuromodulation approaches that directly regulate autonomic and limbic activity.

The vagus nerve serves as a bidirectional conduit between the brainstem and major organs, helping regulate stress, heart activity, and inflammation. Reduced vagal activity is often linked to anxiety symptoms. Auricular tVNS offers a non-invasive way to stimulate the auricular branch of the vagus nerve and engage its central pathways. While past work shows it can quickly change stress responses, few studies have tested its longer term effects. This study evaluated whether daily tVNS could lower anxiety over four weeks, using validated self report questionnaires.

⦁ Design: Randomised, placebo controlled longitudinal study.
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⦁ Participants: N=32 healthy young adults (18–31 years) with moderate to severe anxiety (GAD-7 ≥ 9).

⦁ Intervention:
- Active group: Daily stimulation using a Roga tVNS device, applied for 1-hour sessions twice per day over 4 consecutive weeks.
- Placebo group: Identical sham device that mimicked setup but delivered no effective stimulation.

⦁ Assessment timeline: GAD-7 and STAI-S were administered at baseline, week 2, and week 4.

⦁ Measures:
- Generalized Anxiety Disorder Scale (GAD-7): A validated, self administered 7 item questionnaire assessing generalised anxiety severity (0–21 scale; mild = 5–9, moderate = 10–14, severe ≥15).
- State Trait Anxiety Inventory – State scale (STAI-S): A validated, self administered 20 item questionnaire measuring current state anxiety (20–80 scale; low = 20–37, moderate = 38–44, high = 45–80).

⦁ Statistical analysis: Changes in anxiety scores were compared across the three time points and interpreted against clinical thresholds to determine whether reductions reflected meaningful shifts in severity.

Across the 4 week intervention, participants receiving active auricular tVNS showed sustained reductions in anxiety, with improvements evident by week 2 and consolidating by week 4. Placebo participants showed only modest early reductions that later plateaued or reversed. On the GAD-7, the active group shifted from severe to mild anxiety, while on the STAI-S they moved from high to moderate.

As shown in Figure A, GAD-7 scores began in the severe range (~15) for both groups. By week 2, the active tVNS group demonstrated a sharp reduction to single digit values (~9), while placebo participants remained elevated (~12). At week 4, the active group achieved a 47% reduction from baseline (~8), a clinically meaningful shift into the mild range [t(31)=7.92, p<0.001]. In contrast, placebo scores plateaued in the moderate range, showing no sustained improvement.

In Figure B, STAI-S scores started in the high anxiety range (~49). At week 2, the active group declined to ~44, crossing into the moderate range, whereas placebo participants showed only a minimal decrease. By week 4, the active group reached ~42, a 14% reduction [t(31)=2.85, p=0.008]. Placebo participants, however, exhibited a slight rebound toward baseline, suggesting their early improvement reflected transient expectancy rather than a durable effect.

This longitudinal study demonstrates that daily auricular tVNS can produce sustained reductions in anxiety over a 4 week course, with measurable improvements by the 2-week mark. Both GAD-7 and STAI-S, validated self reported measures, confirmed clinically significant changes.

Vagus Nerve Stimulation represents a promising approach that can deliver longitudinal anxiety relief. Further research should investigate durability beyond 4 weeks and its potential integration with pharmacological, behavioural and mindfulness therapies.

Keywords

Anxiety, Transcutaneous Vagus Nerve Stimulation (tVNS), Generalized Anxiety Disorder (GAD-7), State-Trait Anxiety Inventory, State (STAI-S)