Relationship between disgust and orthorexia nervosa and psychometric properties of the Italian Dusseldorf orthorexia scale in a general population sample

Background: It remains unclear among clinicians and researchers whether orthorexia nervosa (ON) is a part of the obsessive-compulsive disorder spectrum or eating disorders. Disgust seems to be a shared psychopathological factor in these clinical presentations, indicating a potentially crucial role in ON. On the other hand, numerous psychometric tools have been developed to evaluate ON. The Dusseldorf Orthorexia Scale (DOS) was recently validated in an Italian sample. However, the study's primary limitation was that the scale was only administered to undergraduate university students. This study aimed to investigate the psychometric properties (including factorial structure, reliability, and measurement invariance conditional on sex) of the Italian version of the DOS (I-DOS) on a sample from the general population. Additionally, the study sought to determine the nomological validity of the I-DOS by examining its relationship with disgust sensitivity. Methods: A sample of 521 participants took part in this study and completed a battery that assessed ON and disgust sensitivity. To assess the I-DOS structure, reliability, and measurement invariance we respectively conducted confirmatory factor analysis (CFA), computed McDonalds's omega, and performed hierarchical series of multigroup CFAs. Then, we tested the relationship between ON and disgust sensitivity. Results: CFA confirmed the unifactorial model of I-DOS and it respected the configural, metric, and strict invariance while a partial scalar invariance was achieved. It also showed good reliability with an omega of 0.87. In addition, we found a positive relationship between ON and disgust sensitivity, thus confirming the nomological validity of I-DOS. Conclusions: Our findings suggest that the Italian version of the Dusseldorf orthorexia scale (I-DOS) exhibits strong psychometric properties and can be an effective instrument for assessing ON in a general population sample. Notably, the most significant and innovative outcome was the positive correlation between ON and disgust sensitivity. As disgust has been linked to other clinical presentations, this preliminary result could serve as a foundation for future research exploring this phenomenon in greater detail.