An Event-Related Potential Study Of Moral Disgust And Physical Disgust In Obsessive-Compulsive Disorder

Objective Obsessive-compulsive disorder(OCD) is a relapsed and refractory chronic mental illness, which is characterized by recurrent compulsive behaviors and obsessions. Previous studies have found that disgust processing was impaired in OCD. Disgust plays an important role in the pathogenesis of OCD. Disgust can be caused by non-clean material(such as bacteria, excrement, etc.) and behaviors violated social ethics. The morality of OCD is stronger, they are more disgust to immoral behaviors of self and others.In this study, disgust emotion was divided into physical disgust and moral disgust. Neural electrophysiological techniques was used to examine the moral disgust processing in OCD. The aim of our study was to explore characteristics of moral disgust and physical disgust to discuss its relationship between obsessive-compulsive symptoms, another goal of our study was to investigate the behavioral evidence and electrophysiological mechanisms between them.Methods 28 patients who met a ICD-10 diagnosis for OCD and 30 healthy controls matched for gender, age, education completed lexical decision task, recording EEG data and behavioral data by using Neuroscan ERP. All subjects completed Montreal Cognitive Assessment(Mo CA), The Digit Span Test(DS), Stroop Colour Word Test(SCWT), Verbal Fluency Test(VFT), Padua Inventory-Washington State University Revision(PI-WSUR), Hamilton Anxiety Scale(HAMA), and Hamilton depression scale(HAMD-17). Additionally, the OCD patients were assessed by Yale-Brown Obsessive Compulsive Scale(Y-BOCS).Results( 1) Behavior Results: OCD showed higher disgust degree to moral disgust-related words [(7.08±1.23)vs.(5.77±1.44)] and to physical disgust-related words [(6.38±1.78)vs.(5.03±1.64)] than the healthy controls, the differences were statistically significant(P < 0.05); OCD showed longer reaction time to moral disgust-related words [(798.73±115.26)ms vs.(727.00±106.06)ms] and to physical disgust-related words [(762.69±128.25)ms vs.(648.69±162.66)ms] than the healthy controls, the differences were statistically significant(P<0.05); Y-BOCS total scores Y-BOCS obsessive thoughts scores, Y-BOCS compulsive behavior scores, total score of PI-WUSR, cleaning/pollution force factor scores, hurting themselves and others force factor were positively correlated with two types of disgust-related words in patients group(P< 0.05).(2)EEG results: The ANOVA conducted on LPC mean amplitude showed a significant main effect(P <0.05), Analysis of Stimulus type and groups revealed a critical significant interaction effect(P = 0.05); The difference of LPC amplitude induced by physical disgust and moral disgust [(5.35±0.68)μV vs.(5.30±0.84)μV] was not statistically significant in OCD(P>0.05), but it was statistically significant in normal control group(P<0.05). Y-BOCS score, total score of PI-WUSR, cleaning/pollution force factor score, hurting themselves and others force factor were positively correlated with LPC amplitude in OCD(P< 0.05).Conclusion The main findings of this study is the physical disgust and moral disgust of OCD are more intense compared to controls, and they are positively correlated with the degree of clinical symptoms.