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.