Genomic Analysis of Trichotillomania

Trichotillomania (TTM) is a psychiatric condition in which people feel an overwhelming urge to pull out their hair, resulting in noticeable hair loss and significant distress. Twin, family and candidate gene studies suggest that TTM is at least partly genetic, but no genome-wide analyses have been completed. To fill the gap in this field, we have conducted a case-control study of genotype array data from 101 European ancestry TTM cases and 488 ancestry-matched unaffected controls. TTM cases were ascertained in the USA through web-based recruitment, patient support groups, and conferences organized by the Trichotillomania Learning Center. Following clinical confirmation of a TTM diagnosis, patients completed self-report assessments of frequency and duration of hair pulling, other psychiatric symptoms, and family history. Unaffected controls were also ascertained in the USA and were matched to cases by ancestry. In the first formal genome-wide association study of TTM, we did not identify any common variants with a genome-wide significant (P < 5x10-8) association level with case status. We found that TTM cases carry a higher load of common polygenic risk for psychiatric disorders than unaffected controls (P = 0.008). We also detected copy number variants previously associated with neuropsychiatric disorders in TTM cases (specifically, deletions in NRXN1, CSMD1, and 15q11.2). These results further support genetics role in the etiology of TTM and suggest that larger studies are likely to identify risk variation and, ultimately, specific risk genes associated with the condition.