Factor structure of the Eating Disorder Flexibility Index in U.S. nonclinical collegiate and clinical adolescent samples

Cognitive and behavioral inflexibility are transdiagnostic maintaining mechanisms of varied psychopathologies, including eating disorders (ED). The Eating Disorder Flexibility Index (EDFLIX) is the only psychometrically validated self-report measure of general and ED-specific flexibility in the published literature. The EDFLIX was originally developed in Scandinavian adult clinical and healthy control samples but is increasingly used in its English version in other populations, including adolescent and nonclinical samples, raising questions about its validity and reliability in diverse groups. This study examined the factor structure of the previously published English EDFLIX in undergraduates (n = 578, 57.6 % female, 50.2 % White). Parallel and exploratory factor analysis suggested the EDFLIX may comprise two or three underlying factors. However, follow-up confirmatory factor analyses from nonclinical student and clinical ED-diagnosed (n = 69, 87.0 % female, 91.3 % White) samples did not support either model. Further, EDFLIX scores did not correlate with established neuropsychological measures of cognitive flexibility typically used in prior research on flexibility in EDs. Findings suggest the EDFLIX has poor psychometric properties in certain groups and may not capture underlying aspects of flexibility as previously proposed. Future research should explore alternative versions of the EDFLIX along with its psychometric properties across various samples.