Two subtypes of pathological skin-picking: Evidence from a voxel-based morphometry study

Abstract

Research on the neurobiological correlates of skin-picking disorder (SPD) has yielded inconsistent findings. The present voxel-based morphometry (VBM) study investigated whether there are two distinct subtypes of SPD based on the heterogeneity in symptom presentation. While some patients experience the process of picking as positive (e.g., soothing, rewarding), others have negative feelings (e.g., nervousness, tension). We compared grey matter volume (GMV) in regions of interest (e.g., insula) between these two groups of SPD patients. GMV data from SPD patients who described the picking process as pleasant (n = 21; SPD+) or unpleasant (n = 30; SPD-), and healthy control participants (n = 25) were compared with each other. The two SPD groups reported similar symptom severity and duration. Insular volume was found to be reduced in both SPD groups compared to the control group. The SPD-group had less GMV in the insula than the SPD + group. In the operculum, the SPD-group showed increased GMV compared to the SPD + group and the control group. The operculum and the posterior insula are involved in touch processing (differentiating self-generated from externally generated touch; attenuation vs. enhancement of touch information). This study is a first attempt to delineate SPD subtypes based on clinical and neuroanatomical features. Future research needs to demonstrate the reliability of SPD subtyping.