Etiology of Trichotillomania in Monozygotic and Dizygotic Twins (An integrated Genetic, Environmental and Behavioral Model)

Abstract

Trichotillomania is a clinical psychiatric manifestation involving significant hair loss in association with recurrent hair-pulling behavior, the etiology of which is still unknown. The aim of this study was to investigate the genetic and environmental and behavioral contribution to trichotillomania (hair-pulling disorder) and to relate the findings to contemporary theories about the etiology. This was a descriptive correlational and twins study design. 672 twins (MZ=474; DZ=202) were selected from Iranian twins associations in 2018. The Massachusetts General Hospital Hair-pulling Scale(1995) and the Self-Report of Zygosity were used as research instrument. Twin modeling methods were employed to decompose the variance in the liability trichotillomania (hair-pulling disorder) into additive genetic and shared and non-shared environmental factors. The data was analyzed by SPSS, STATA and M-plus. Univariate model-fitting analyses showed that genetic factors accounted for approximately 64% of the variance in TTM. The best extracted model for TTM was the DE model. The correlation coefficient results indicated that the correlation rate was 0/61 and 0/31 in MZ and DZ group respectively. It can be concluded that TTM phenotype is the results of a polygenetic. There is no intermediate despite of the dominance effect and it results from a gene-gene interaction or a dominant gene.

Keywords

• monozygotic twins
• dizygotic twins
• obsessive compulsive disorders
• hair-pulling disorder
• environmental and behavioral.