Autonomic profile under hypnosis as assessed by heart rate variability andspectral analysis

To test the hypothesis of a sympathovagal balance shift towards an enhanced vagal tone under the condition of a standardized hypnosis, we used the ass essment of heart rate variability including spectral analysis in 10 healthy subjects (5 female, 5 male, age ranging from 27 to 42 years). We compared the subjects under baseline condition (resting) and under hypnosis, measure d on a different day, for a measuring period of five minutes for each condi tion. The result was reduced total power in the low frequency band (0.01-0. 05 Hz) reflecting sympathetic activity. Also, the ratio of low to high freq uency power (LFIHF) was reduced when under hypnosis. This reduction was due to a reduced LF component, but only a slightly reduced mid frequency compo nent. With considerable variability, we also found activated mid frequency bands (0.05-0.15 Hz) under hypnosis, likely reflecting baroreceptor activit y. We conclude that the autonomic status in hypnosis is associated with a c hange towards reduced low frequency activity, but not necessarily with enha nced high frequency activity.