Objectives
The purpose of this study is to assess the effect of taegeuk acupuncture on reducing mental stress by analyzing heart rate variability in soeumin.

Methods
Six soeumin-diagnosed men participated in this study. They were randomly divided into group A and group B. Each participant went through 4 sessions every week with 1 week of washout period in between each session. HRV was measured three times at every session; at baseline, after administering mentally stressful circumstances and after applying soeumin taegeuk acupuncture or soyangin taegeuk acupuncture. This study was designed as a crossover clinical trial. Group A participants were treated with two sets of soeumin taegeuk and soyangin taegeuk acupuncture treatment in respective order (i.e. soeumin taegeuk - soyangin taegeuk - soeumin taegeuk - soyangin taegeuk acupuncture treatment). Group B participants were treated with reverse-ordered acupuncture treatment (i.e. soyangin taegeuk - soeumin taegeuk - soyangin taegeuk - soeumin taegeuk acupuncture treatment ). Bayesian analysis was performed by using WinBUGS(Ver. 1.4.3) for comparison between soeumin taegeuk acupuncture and soyangin taegeuk acupuncture.

Results
Overall, soeumin taegeuk acupuncture tends to reduce LF/HF ratio, LF, HF, LF(Norm) and increase HF(Norm) more than soyangin taegeuk acupuncture, but the difference was not statistically significant. In one participant, however, soeumin taegeuk acupuncture reduced LF/HF ratio, LF(Norm) and increased HF(Norm) more than soyangin taegeuk acupuncture, and the difference was stastatistically significant.

Conclusions
This study suggests that soeumin taegeuk acupuncture might be an effective means of stabilizing mental stress-induced imbalance of autonomic nervous system for soeumin.