Tracking the shift from health to harm: Development and validation of a short screening tool for orthorexia nervosa (STONE)

Orthorexia Nervosa (ON), a problematic fixation on healthy eating, has captured researchers' attention for over a decade. We aimed to develop a brief screening tool for ON that captures physical appearance as a motivating factor, behavioural aspects (rigid control over food selection, consumption and preparation), and nutritional aspects (avoidance of foods considered “impure”). Using a sequential, iterative design, 687 participants completed a self-reported survey across four studies: item identification and selection through exploratory factor analysis (n = 248), testing factorial construct validity with confirmatory factor analysis (n = 127), discriminant validity via known group differences (n = 241), and test-retest reliability of two subsequent administrations of the selected items (n = 71). The final unidimensional version of the short Screening Tool for Orthorexia Nervosa (STONE) comprises eight items. It demonstrated excellent known-group validity and ability to differentiate ON from other types of strict dietary control (e.g., health-based or religious restrictions). Consistent with the view of ON as behaviours aimed at rigid dietary control, avoidance of "impure" foods, and motivation to enhance physical appearance, STONE scores positively related to measures of eating pathology and appearance orientation, while only weakly correlating with obsessive-compulsive tendencies. Based on its psychometric properties, STONE is recommended as a first-level screening tool for ON in research contexts and epidemiology studies among adults. Due to its brevity, it can be easily combined with other scales to explore ON or related phenomena. Future studies should examine convergent validity and test it among adolescents and in different cultural contexts.