Excoriation disorder is the repetitive scratching or picking of skin that leads to physical damage, distress, and functional impairment. Skin picking has been associated with impulsivity and problems with inhibition. We hypothesized that problems in these areas could be disease severity markers. We recruited 73 adults meeting DSM-5 criteria for excoriation disorder, and 50 adult controls. Those with excoriation disorder were categorized as either “high impulsive” (HI) or “low impulsive” (LI) using either a neurocognitive task of motor impulsivity (Stop Signal Task) or the Barratt Impulsiveness Scale's (BIS-11) motor impulsivity subscale. The HI subjects, based on the BIS-11, showed higher urges scores, anxiety, and depressive symptoms. These data suggest that impulsivity may reflect a specific clinical presentation among those with excoriation disorder, but the clinical characteristics differ depending upon the impulsivity measure used. Agreement on how to measure various domains of impulsivity may be important in better understanding the disorder psychopathology and so improve future treatments.
Excoriation Disorder, also known as Skin Picking Disorder, is characterized by the repetitive and compulsive scratching or picking of skin, which causes tissue damage (Arnold, Auchenbach, & McElroy, 2001; Grant et al., 2012). Excoriation may result in infections, scars and therefore embarrassment and social isolation. Recently, excoriation disorder was included in the Diagnostic and Statistical Manual – 5th edition (DSM-5) in the category of “Obsessive and compulsive, and related disorders” (American Psychiatric Association, 2013).
Despite being arguably quite common, excoriation disorder has not been well studied. Two community prevalence studies have been published, and both found notable rates of excoriation disorder. The first one used a nonclinical community sample of 354 people and found that 5.4% reported significant picking, meeting all DSM-5 criteria (Hayes, Storch, & Berlanga, 2009). The other study, based on 2513 telephone interviews, found 1.4% met all DSM-5 criteria for excoriation disorder (Keuthen, Koran, Aboujaoude, Large, & Serpe, 2010).
So far, there is no clear neurobiological explanation for the etiology and maintenance of this disruptive behavior. The only neuroimaging study on excoriation disorder used diffusion tensor imaging and showed bilateral abnormalities in the anterior cingulate cortex and abnormalities on the left temporoparietal junction – neural circuits involved in the generation and suppression of motor responses (Grant, Odlaug, Hampshire, Schreiber, & Chamberlain, 2013).
Recent research examining neurocognition in excoriation disorder has shown deficits in motor inhibition, which appears to be correlated with frontal cortex abnormalities. One study found impaired inhibitory control in excoriation disorder subjects compared with healthy controls (assessed using the CANTAB Stop-Signal Task-SST) (Odlaug, Chamerlain, & Grant, 2010). Another study, comparing excoriation disorder, trichotillomania and healthy controls showed greater inhibitory deficits in excoriation disorder, and the deficits were associated with greater severity of excoriation (assessed using the CANTAB SST and the Clinical Global Impressions scale-CGI) (Grant, Odlaug, & Chamberlain, 2011). Furthermore, severity of excoriation disorder may be associated with higher levels of impulsivity (assessed by the BIS-15, a shorter revision of BIS-11) but which domain of impulsivity, and how to measure it, remains unclear (Adams, 2012 and Hayes et al., 2009; Patton, Stanford, & Barratt, 1995; Spinella, 2007).
The clinical relevance of impaired motor control to excoriation disorder, therefore, remains unclear. Because previous data implicate impairment in inhibitory control in repetitive picking behavior, we hypothesized that impaired inhibition would be associated with excoriation disorder severity.
This study provides relevant clinical and research data that within excoriation disorder, gradations of impulsivity may reflect important clinical differences on an individual level. It also raises important questions, however, about how best to assess the various domains of impulsivity. Ultimately, knowledge of what cognitive variables (and how to best measure them) drive the different levels of excoriation severity may aid in early prevention efforts and improved treatment, both, pharmacological or psychotherapeutic.
