Development and validation of the self-directed moral disgust scale in a large italian non-clinical sample

Objective: Mental contamination (MC) has been described as an internal experience of dirtiness that can arise and persist in the absence of contact with observable physical contaminants. Recent research suggested that perceiving the self as disgusting, as a result of internalizing the disgust experienced during a sexual assault, was predictive of MC and that MC typically includes elements or judgements related to morality/immorality. We then hypothesized that a self-directed form of moral disgust may play a critical role in MC. Unfortunately, no validated measure specifically assesses this construct. We developed a new measure - the Self-Directed Moral Disgust Scale (SD-MDS) - aimed at assessing this construct, and validated it by testing its factorial structure, reliability and construct validity in a large Italian non-clinical sample. Method: For this study, 604 volunteers (54% females) were recruited from the general population (mean age: 38.28, SD: 14.67). The 32-item SD-MDS, the Three Domains of Disgust Scale, the Disgust Propensity Questionnaire, and the Depression Anxiety Stress Scales-21 were administered. Results: Scale refinement through exploratory factor analysis and item analysis led to the final 20-item version of the scale. It showed a unidimensional structure - all of the items substantially (i.e., ≥.54) loaded on the first factor, which explained 43% of the variance - excellent internal consistency and construct validity. Conclusions: We provided preliminary evidence that the SD-MDS is a unidimensional reliable scale that assesses the self-directed form of moral disgust. Future studies should investigate its psychometric properties in clinical samples and test the hypothesized associations with MC measures.