A cognitive comparison of pathological skin picking and trichotillomania

Pathological Skin Picking (PSP) and Trichotillomania (TTM) share overlapping comorbidity and phenomenology. The extent to which these disorders share a common cognitive phenotype, however, has yet to be examined. This study sought to compare inhibitory control processes in individuals with PSP or TTM.

Thirty-one subjects with PSP (mean age 31.2 ± 12.5 years; 93.5% female), 39 subjects with TTM (mean age 35.9 ± 10.7 years; 87.2% female), and 33 matched controls (mean age 31.9 ± 9.9 years; 72.7% female) undertook cognitive assessments using the Stop-Signal Task (assessing response impulsivity) and the Intra-dimensional/Extra-dimensional (ID/ED) Set Shift task (assessing cognitive flexibility). Groups were matched for age, gender, race/ethnicity, and education.

PSP was associated with significantly impaired stop-signal reaction times but intact ID/ED cognitive flexibility compared to controls. TTM occupied an intermediate position in terms of stop-signal reaction times between controls and PSP but did not differ significantly from either group on the ID/ED Set Shift Task.

These results replicate the finding of impaired inhibitory control in PSP but suggest TTM may be heterogeneous with respect to such impairment. Future work should explore possible subgroups in TTM and whether cognitive variables are predictive of treatment outcomes.