Study Finds Genetic Basis for Repetitive Hair-Pulling and Skin-Picking Disorders

Repetitively pulling out hair or picking at the skin is not simply a “bad habit” but a neurobiological disorder with a genetic basis, according to a new study. Researchers at Yale School of Medicine analyzed DNA from more than 100 parent-child families affected by trichotillomania and excoriation disorder. Their findings were published in June in the international journal Translational Psychiatry.

These two disorders are classified as body-focused repetitive behaviors (BFRBs). Both the DSM-5 and ICD-11 currently clearly classify BFRBs as a subcategory of obsessive-compulsive and related disorders, and an estimated 1% to 3% of the global population is clinically significantly affected. Some studies have also found that, including mild symptoms, more than half of the population experiences these behaviors at least once during their lifetime.

■ OCD genetic risk inherited from parents

The researchers used a “trio” approach, collecting DNA from children with the disorders and their biological parents. When they analyzed whether specific genetic risk factors were passed to children more often than would be expected by chance, they found that patients with BFRBs were more likely to inherit higher polygenic scores for obsessive-compulsive disorder (OCD) from their parents.

Notably, this additional inheritance of OCD-related genetic risk was also identified in patients with BFRBs who did not have co-occurring OCD. This suggests that a shared biological basis may exist even in people who do not have both diagnoses, supporting evidence of a neurobiological link between BFRBs and OCD.

■ Rare variants found in genes involved in synaptic connections

The researchers also identified rare copy number variants (CNVs) in some patients with BFRBs. These are regions in which portions of DNA are deleted or duplicated, and some have previously been observed in neurodevelopmental disorders. Several of the genes involved were associated with how brain cells form connections, namely synapse formation and organization.

Study senior author Emily Olfson, a professor at Yale School of Medicine, said, “Some genes help neurons build and organize connections,” adding that the finding “is consistent with existing evidence that synapse-related biology may be important in these behaviors.” Olfson also emphasized, “These disorders are never anyone’s fault, and although genetic and biological factors clearly exist, genetic risk does not mean destiny.”

BFRBs typically first appear in late childhood or early adolescence, at an average age of 10 to 13 years. Based on clinical reports in adulthood, 80% to 90% of patients are women. Researchers believe this is because women, who may be more sensitive to visible effects such as hair loss or skin scarring, are more likely to seek medical care.

■ Evidence for reducing stigma and shifting treatment approaches

The findings also have significance for reducing the social stigma surrounding BFRBs. Patients and families have long faced the misconception that these behaviors result from a lack of willpower or poor parenting. The International OCD Foundation (IOCDF) said, “Despite their high prevalence and extreme distress, BFRBs have historically been among the most understudied and underfunded mental health conditions,” and assessed the genetic findings as a milestone toward personalized treatment.

In South Korea, symptoms such as nail-biting or hair-pulling during childhood and adolescence are still often viewed as “habits that need to be corrected,” rather than neurological disorders, leading some families to try to address them through coercive discipline. As a high-pressure, highly competitive educational environment increases anxiety and stress among adolescents, it may act as a powerful trigger that initiates or worsens symptoms in children with a genetic predisposition.

Industry experts believe that as the genetic causes of BFRBs become more clearly defined, opportunities will emerge to develop new drug treatments targeting specific neural pathways or synapses in the brain. Some also predict that, as follow-up studies involving larger and more ethnically diverse populations accumulate, BFRBs could be subdivided into subtypes such as sensation-seeking and unconscious-urge types, making personalized treatment based on patients’ genetic profiles a global standard.

The researchers emphasized the need for follow-up studies combining DNA sequencing, detailed clinical assessments and long-term observation. The study also represents the contributions of more than 100 families affected by trichotillomania and excoriation disorder who participated voluntarily and shared their time and experiences.