Investigating the familiality of trichotillomania and excoriation disorder.

Trichotillomania (TTM) and excoriation disorder (ED) run in families and are thought to have shared etiological underpinnings. Only a few small studies have compared the family history of individuals with TTM, ED, and both conditions. To better understand shared predispositions, we examined self-reported family history of mental health disorders using cross-sectional survey responses from a genetics study of probands ages 4-66 years with TTM only (n = 69), ED only (n = 34), and both conditions (n = 70). Individuals with TTM only reported higher rates of having a first-degree relative with TTM (25 %, 17/69) compared to individuals with ED only (6 %, 2/34) (p = 0.03). Those with ED only reported higher rates of a first-degree relative with ED (41 %, 14/34) compared to individuals with TTM only (13 %, 9/69) (p = 0.002). Individuals with both conditions reported high rates of first-degree relatives with TTM (21 %, 15/70) and ED (39 %, 27/70). All three groups reported high rates of family history of anxiety (48 %-59 %), depression (41 %-49 %), ADHD (23 %-31 %), and OCD (17 %-18 %). Comparing mental health history in parents, there were no significant differences between the parents for TTM or ED, but mothers had higher rates than fathers of anxiety (42 % maternal vs. 18 % paternal) and depression (34 % maternal vs. 14 % paternal) (p-values < 0.001). Our results provide evidence of both shared and distinct predispositions between TTM and ED, highlighting the need for further research on genetic and environmental factors contributing to these conditions.