The Nepean Belief Scale (NBS) as a tool to investigate the intensity of beliefs in anorexia nervosa: psychometric properties of the Italian version.

Background: People with anorexia nervosa (AN) show a peculiar impairment of insight regarding their condition, often manifesting a denial of extreme emaciation and sometimes hiding or underreporting socially undesirable abnormal eating patterns. Sometimes the intensity of the beliefs held by patients with AN reach a delusional intensity.

Objectives: In this study, the Italian version of the Nepean Belief Scale was applied to a sample of patients diagnosed with AN to investigate the intensity of their beliefs and convictions and its clinical correlates.

Methods: The Nepean Belief Scale (NBS) was translated and adapted to Italian and applied to a sample of patients diagnosed with AN based on the Structured Clinical Interview for DSM-5 (SCID-5).

Results: The Italian version of the 5-item NBS showed excellent reliability. Convergent validity was proved by negative association with levels of insight measured with the Schedule for the Assessment of Insight in Eating Disorders. Beliefs of delusional intensity were reported by 10% of participants. Those with a greater intensity of beliefs, either overvalued or delusional ideas, were more likely to report poorer general cognitive performances on the Montreal Cognitive Assessment. No association was observed between NBS score and age, body mass index, symptoms of eating disorders, body dissatisfaction, or levels of depression. Fear of weight gain and control seeking were the most often reported themes at the NBS.

Conclusions: The Italian version of the NBS is a reasonably reliable, valid, and usable tool for the multidimensional assessment of insight in AN. Level of evidence Level III, Evidence obtained from well-designed cohort or case-control analytic studies.