Fig. 3.

Change in long-term heart rate variability (SD2) for multiple stimulation protocol following traumatic stress (four traumatic stress and six stimulation administrations on the first day). Bars represent the unadjusted mean changes from baseline, error bars: 95% confidence interval (CI), values calculated from raw data, * indicates p < 0.05. β coefficients, adjusted CI, effect sizes (d), and p-values were reported in β (±CI, d, p) format. Active tcVNS group experienced decrease in SD2 after the multiple stress protocol by 31.7 ms (±15.5 ms, d = 1.02, p = 0.026) after adjustments.