Neurobiology of Subtypes of Trichotillomania and Skin Picking Disorder

OBJECTIVE: Trichotillomania and skin picking disorder are common and often debilitating mental health conditions, grouped under the umbrella term of body focused repetitive behaviors (BFRBs). Recent clinical subtyping found that there were three distinct subtypes of trichotillomania and two of skin picking disorder. Whether these clinical subtypes map on to any unique neurobiological underpinnings however remains unknown. METHODS: 251 adults (193 with a BFRB [85.5% (n=165) female] and 58 healthy controls [77.6% (n=45) female]) were recruited from the community for a multi-center between-group comparison using structural neuroimaging. Differences in whole brain structure were compared across the subtypes of BFRBs, controlling for age, sex, scanning site and intracranial volume. RESULTS: When the subtypes of TTM were compared, low awareness hair pullers demonstrated increased cortical volume in the lateral occipital lobe relative to controls and sensory sensitive pullers. In addition, impulsive/perfectionist hair pullers showed relative decreased volume near the lingual gyrus of the inferior occipital-parietal lobe compared to controls. CONCLUSIONS: These data indicate that the anatomical substrates of particular forms of BFRBs are dissociable, which may have implications for understanding clinical presentations and treatment response.