Etiology of Obsessive Compulsive Disorders Spectrum in Monozygotic and Dizygotic Twins (An integrated Genetic, Environmental and Behavioral Model)

Khorramdel, Kazem and Barahmand, Usha and Abolghasemi, Abbas (2016) Etiology of Obsessive Compulsive Disorders Spectrum in Monozygotic and Dizygotic Twins (An integrated Genetic, Environmental and Behavioral Model). Doctoral thesis, University of Mohaghegh Ardabili.

Text (سبب¬شناسي اختلالات طيف وسواس در دوقلوهاي همسان و غير همسان (ارائه مدل يکپارچه ژنتيکي، محيطي و رفتاري)) Kazem Khorramdel.pdf Download (1MB)

Abstract

The new DSM-5 “Obsessive-Compulsive and Related Disorders” chapter contains a series of conditions thought to be etiologically related to obsessive-compulsive disorder (OCD). The aim of this study was to investigate the genetic and environmental contribution to obsessive compulsive disorder and related disorders, and to relate the findings to contemporary theories about the etiology of obsessive compulsive disorder. This was a twins study design. 672 twins (Mz=474; DZ=202) were selected from twins associations of some cities in Iran in 2015. The Obsessive-Compulsive Inventory–Revised,the Yale- Brown Obsessive Compulsive Scale Modified for BDD, the Hoarding Rating Scale, the MassachusettsGeneral Hospital Hairpulling Scale, the Skin Picking Scaleand the Self-Report of Zygosity were used as research instrument.Twin modeling methods were employed to decompose the variance in the liability to Obsessive-Compulsive disorder(OCD), body dysmorphic disorder (BDD), hoarding disorder (HD), trichotillomania (hair-pulling disorder) (TTM)andexcoriation (skin-picking) disorder (SPD)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 44%,36%, 54%,64% and 80% of the variance in OCD, BDD, HD, TTM and SPD Respectively with nonsharedenvironmental factors and measurement error accountingfor the remaining variance. Sharedenvironmental factors were negligible. The best extracted model for OCD, BDD and HD was the AE model,whilst the DE was the best fitted model for TTM and SPD. The results indicated tha e OCRDs have a moderate to strong heritability. herefore, family and molecular genetic studies are required to delineade the role of candidate genes and nonshared environmental factors. Furthur our findings cast some doubts about he common etiology of OCRDs indicaeded in the DSM-5.

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