• Korean Journal of Biological Psychiatry
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• v.18 no.4
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• pp.260-266
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• 2011

Objectives The second to fourth digit ratio (2D : 4D) is known to reflect testosterone level during intrauterine period. Testosterone is essential for masculinization of brain. Cloninger's type II alcoholism is characterized by early age at onset and largely limited to males. Compared with type I alcoholism, type II alcoholism is thought to be masculine. There is a possibility that the digit ratio of type II alcoholism is low compared with type I. We examined digit length ratio in Cloninger's type I and II alcoholism to understand the effects of intrauterine testosterone on the development of alcoholism. Methods The participants were 87 alcohol dependent patients. We divided two subtypes of patients by Irwin's symptom list, based on Cloninger's concept. We captured the images of both palms by the scanner and measured the lengths of digits by the graphic program. Then we analyzed the digit ratios by independent-sample t-test. Results The mean 2D : 4D of type I was 0.942 (right), 0.952 (left). The mean 2D : 4D of type II was 0.927 (right), 0.940 (left). In both hands, 2D : 4D of type II was significantly lower than type I. Conclusions Type II alcoholism showed masculine type of digit length ratio compared with type I. It suggests the exposure of testosterone during intrauterine period might play an important role in determining the course and feature of alcoholism.

• Korean Journal of Biological Psychiatry
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• v.21 no.4
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• pp.151-160
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• 2014

Objectives Prenatal testosterone is known to influence both cerebral laterality and 2nd to 4th digit ratio (2D : 4D). Epigenetic changes are thought to play some role in it. We studied sex-related differences between 2D : 4D and cerebral laterality in patients with schizophrenia and controls to examine the effects of prenatal testosterone in the development of schizophrenia. Methods Forty one men (18 schizophrenic patients and 23 controls) and 40 women (17 schizophrenic patients and 23 controls) were recruited from one psychiatric hospital in Korea. The 2D : 4D and electroencephalographic (EEG) coherence in 19 channels (66 pairs of interhemispheric coherence and 54 pairs of intrahemispheric coherence) were measured. The sex-related statistical analyses between 2D : 4D and EEG coherence in controls and patients with schizophrenia were performed using multiple regression. Results In male patients, the relationship between 2D : 4D and right intrahemispheric EEG coherence showed mainly positive correlation in delta and theta frequency bands, while it showed negative correlation in male controls. In female patients, the relationship between 2D : 4D and interhemispheric EEG coherence showed stronger positive correlation in alpha and beta frequency bands, while it showed weaker positive correlation in female controls. Conclusions Low prenatal testosterone may play certain roles in altered correlation between 2D : 4D and cerebral laterality in schizophrenia and the development of schizophrenia by epigenetic mechanism.

• Korean Journal of Biological Psychiatry
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• v.17 no.1
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• pp.37-43
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• 2010

Objectives : The $2^{nd}$ to $4^{th}$ digit length ratio(2D : 4D) is a sexually dimorphic trait regardless of ethnicity and shows sex differences. According to previous research, men usually have a relatively shorter $2^{nd}$ digit than $4^{th}$ digit. There is tendency that men with lower 2D : 4D are perceived as being more masculine and tend to perform better in some physical sports. Furthermore, 2D : 4D is negatively associated with trait aggression. In this study, we examine gender difference of 2D : 4D and compare 2D:4D of female Korean national team members to 2D : 4D of control subjects. Besides that, we also compare 2D : 4D of female Korean national team members according to their sports entries. Methods : The sample of this study is 396 people, 67 female Korean national team member, 216 control women and 113 control men. We measured $2^{nd}$ to $4^{th}$ digit length of their right hand. In addition, we collected demographic information of female Korean national team members using a self-report questionnaire. Results : The mean 2D : 4D of female Korean national team members is 0.96(SD=0.04), smaller than control women's 2D : 4D(0.97, SD=0.03) and significantly higher than control men's 2D : 4D(0.95, SD=0.03). We also found differences between control men and women. Non-martial arts related sports athletes have significant difference with control men in 2D : 4D. However, martial arts related sports athletes' 2D : 4D is not significantly different from other groups, including control men. Conclusion : These results are consistent with the findings of previous research that there is a significant difference between men and women in their 2D : 4D. Furthermore, 2D : 4D of martial arts related sports athletes have not shown any difference from the 2D : 4D of control men that 2D : 4D of non-martial arts related athletes have shown. This fact is important in consideration of masculine characteristics. For further research, it is necessary to examine 2D : 4D difference according to sport ability and gender differences.

• Korean Journal of Biological Psychiatry
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• v.24 no.3
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• pp.142-148
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• 2017

Objectives The ratio of second to fourth digit length (2D : 4D) could be a potential epigenetic marker of sexual dimorphism reflecting prenatal testosterone exposure. Testosterone is known to affect the development of the brain through an epigenetic mechanism. The purpose of this study was to investigate the effects of exposure to fetal testosterone on the metabolic syndrome based on 2D : 4D of schizophrenia patients and the relationship with the age of onset of schizophrenia. Methods A total of 214 schizophrenia patients participated in this study. The participant's physical and blood tests were performed according to the American National Cholesterol Education Program's Third Amendment of the Metabolic Syndrome Diagnostic Criteria, and the 2D : 4D was measured by the method designed by McFadden. Data were statistically analyzed by t-test, Pearson's correlation analysis and multiple regression model analysis. Results 2D : 4D was significantly higher in female than male in both hands, and there was a statistically significant negative correlation between 2D : 4D and the age of onset of schizophrenia in male. However, 2D : 4D did not show statistically significant correlation with metabolic factors. Conclusions Fetal testosterone suggests the possibility of affecting the age of onset of schizophrenia through the epigenetic mechanism, but there is no clear relationship with metabolic factors.