Recently it has been reported that the prevalence of hwabyung is increasing in Korean young adults. The purpose of the present study was to estimate genetic and environmental influences on Hwabyung-personality, a risk factor for the development of hwabyung. Hwabyung-personality is characterized by high levels of anger, impulsivity, harm-avoidance, social reward, and self-transcendence and a low level of self-directedness.

The hwabyung-personality scale was administered to 1476 twins [mean (SD) age=18.9 (±3.1 years)] via a telephone interview. Maximum likelihood twin correlations were computed and model- fitting analyses were performed.

Monozyogotic (MZ) twin correlations were significantly higher than dizygotic (DZ) twins in hwabyung-personality scale in males and females, suggesting the presence of genetic influences on hwabyung-personality. DZ twin correlations were close to zero, indicating that genetic influences on hwabyung-personality are non-additive and that shared environmental infleunces are negligible. Model-fitting analysis revealed that genetic and non-shared environmental influences on hywabyung- personality were 39% (95% CI=30%, 48%) and 61% (95% CI=54%, 69%), respectively. These estimates were not significantly different between males and females.

Genetic influences on hwabyung-personality found in the present study suggest that genetic vulnerability should be incorporated in prevention as well as treatment of hwabyung symptoms.

The purpose of the study was to explore whether the effect of Huanglian-jie-du granule depends on the baseline heart rate variability in patients with Hwa-byung.

We used the supplementary data from a randomized, double-blind, placebo-controlled trial of Huanglian-jie-du granule for Hwa-byung patients. Study drugs were taken orally three times per day for one week. Heart rate variability was measured three times; before the treatment, after the treatment, and month follow-up period. Spearman’s rho test was done to explore the role of the baseline heart rate variability to the effect of Huanglian-jie-du granule.

Baseline low frequency power of heart rate variability was negatively correlated with the reduction of the insomnia severity index in experimental group (r=−0.493 p=0.02). Also, Huanglian-jie-de granule significantly decreased the low frequency power of heart rate variability in patients with Hwa-byung compared to placebo (mean difference 266 [95% CI: 29∼503], p=0.028). In Hwa-byung symptoms, stuffy, pushing up in the chest, and flush of anger were correlated with low frequency power of heart rate variability (p=0.010, p=0.000, and p=0.016, respectively).

The effect of the Huanglian-jie-de granule for insomnia seems to be lower when the baseline low frequency power of heart rate variability is higher in Hwa-byung patients. Also, Huanglian-jie-de granule is likely to decrease the sympathetic activity in patients with Hwa-byung. Measurement of heart rate variability may be the useful to understand the state of Hwa-byung patients.