For the millions of people who pull their hair or pick their skin compulsively, the question of whether these behaviors reflect a distinct biological disorder — or a variant of OCD — has long shaped treatment approaches. New genomic evidence from family trios offers the clearest genetic signal yet that these conditions share meaningful molecular architecture with obsessive-compulsive disorder, which could refocus how clinicians conceptualize and eventually treat them.
The study enrolled 110 parent-offspring trios — 334 individuals total — in which the proband carried a diagnosis of trichotillomania, excoriation disorder, or both. Using genome-wide array data, researchers applied the polygenic transmission disequilibrium test (pTDT) to measure whether polygenic scores derived from OCD genome-wide association studies were disproportionately inherited by affected offspring versus their unaffected parents. Among 92 European-ancestry trios, the OCD polygenic score showed statistically significant over-transmission (mean pTDT = 0.36, p = 0.01). Polygenic scores for depression, anxiety, and ADHD did not reach significance. Additionally, several rare copy-number variants overlapping genes intolerant to loss-of-function mutations were identified in probands, suggesting a role for rare high-impact variants alongside common ones.
This finding is incremental but meaningful within a sparse evidence base. Body-focused repetitive behaviors have historically been under-studied genetically relative to OCD itself, partly due to challenges in case ascertainment. The trio-based pTDT design is well-suited to small samples because it controls for population stratification without requiring a large external control group — a genuine methodological strength. However, the cohort of 110 families is modest, limiting power to detect effects from other psychiatric polygenic scores that might still be relevant. The exclusive focus on European ancestry also constrains generalizability. The rare CNV findings are hypothesis-generating rather than conclusive. Cumulatively, this work supports the current DSM-5 classification of BFRBs as OCD-spectrum conditions on genetic grounds — a validation with potential implications for extending OCD-targeted pharmacological and behavioral interventions to these often-overlooked disorders.