Etiology of Skin Picking Disorder in Monozygotic and Dizygotic Twins (An Integrated Genetic, Environmental, and Behavioral Model)

The new DSM-5 “Obsessive-Compulsive and Related Disorders” chapter contains a series of conditions supposed to be etiologically related to obsessive-compulsive disorder (OCD). This study aimed to investigate the genetic and environmental contribution to Skin Picking Disorder and relate the findings to contemporary theories about the etiology of obsessive-compulsive disorder.

This research was a twin study design. 672 twins (Mz=474; DZ=202) were selected from twins associations in some cities in Iran in 2019. The Skin Picking Scale and the Self-Report of Zygosity were used as the research instruments. Twin modeling methods were employed to decompose the variance in the liability to excoriation (skin-picking) disorder (SPD) into additive genetic and shared and non-shared environmental factors. SPSS-26, Stata-17 and M-plus version 8.3.2 analyzed the data.

Univariate model-fitting analyses showed that genetic factors accounted for approximately 80% of the variance in SPD, whereas non-shared environmental factors and measurement error were responsible for the remaining variance. Shared environmental factors were negligible. The best-fitted model for SPD was DE.

The results indicate that SPD has a strong heritability. Therefore, family and molecular genetic studies are required to delineate the role of candidate genes and non-shared environmental factors.