Increased tactile sensitivity and deficient feed-forward inhibition in pathological hair pulling and skin picking

An increasing body of evidence has linked pathological body-focused repetitive behaviors (BFRBs) to excessive sensory sensitivity and difficulty modulating sensory inputs. Likewise, neurobiological evidence points to deficits in feed-forward inhibition and sensory habituation in conditions with similar symptomatology. There is currently little evidence regarding potential physiological sensory abnormalities in BFRBs. The current study compared 46 adults with pathological hair pulling and/or skin picking to 46 age-matched healthy control participants on a series of self-report measures and objective psychophysical tests of neurophysiological sensory functions. Persons in the BFRB group reported increased scores on the Sensory Gating Inventory (U = 320.50, p < .001) and all of its subscales (all p-values < .001), reflecting abnormal sensory experiences. The BFRB group also showed decreased tactile thresholds (increased sensitivity) (F[1, 76] = 10.65, p = .002, η_p² = .12) and deficient feed-forward inhibition (F[1, 76] = 5.18, p = .026, η_p² = .064), but no abnormalities in quickly-adapting sensory habituation were detected on an amplitude discrimination task. Performance on objective psychophysical tests was not associated with self-reported sensory gating symptoms or symptom severity. Implications of these results for the pathophysiology of BFRBs and related disorders are discussed.