Neuroanatomical correlates of impulsive action in excoriation (skin-picking) disorder

Neuroimaging studies have implicated a relationship between skin picking disorder and structural abnormalities within the brain. This study used MRI imaging of people with SPD and compared it to those without SPD. Results suggest that greater motor impulsivity in individuals with SPD relates to structural variation particularly within the insular cortex and parietal and occipital regions of the brain and calls for more research in this field.

This study was the first to evaluate the association between neurocognitive function and structural abnormalities in the neural structures specifically with those who have a primary diagnosis of skin picking disorder.

Men and women between the ages of 18-65 years old were recruited to be participants in the study. The main criteria of participants with SPD was a current diagnosis of SPD, engagement in skin picking behaviors for at least 30 minutes a day consistently during the past 12 months and a score of >16 on the Yale-Brown Obsessive-compulsive Scale modified for Neurotic Excoriation. Each participant was put through a clinical assessment and evaluation by a practicing psychiatrist to developed a baseline and validate a primary diagnosis of skin picking disorder with no co-morbidities. Participants underwent structural brain MRIs which focused on identifying cortical thickness and volume of subcortical structures.

Compared to the control groups, participants with SPD displayed significantly higher levels of depression and anxiety as well as a significantly lower quality of life. Scores of cognitive flexibility and response impulsivity, also measured during the evaluation, proved to differ insignificantly from the control groups. Within the SPD groups, the study identified a relationship between response inhibition and cortical thickness.

During the study, MRI results did not survive multiple testing correction using a false discovery rate. This could be a result of having a small sample size. Although participants scored well below the threshold for clinically significant mood disorders and anxiety, it is worth noting that the SPD group scored generally higher on these tests than the control groups. More studies are needed to solidify the correlative data from this study.

In conclusion, this study suggests that greater motor impulsivity in individuals with SPD relates to structural variation particularly within the insular cortex and parietal and occipital regions of the brain, a finding which is consistent with previous studies of OCD and OCD related disorders. Results suggest that cortical thickness in these regions of the brain may play a role in the pathophysiology of SPD.