Intolerance of uncertainty and repetitive negative thinking: transdiagnostic moderators of perfectionism in eating disorders

Perfectionism has been identified as a vulnerability and maintenance factor across eating disorders (EDs). Additionally, research has found that intolerance of uncertainty (IU) and repetitive negative thinking (RNT) moderate the relationship between perfectionism and psychopathology. Despite this evidence, few studies have examined if these factors specifically moderate ED severity. This study aimed to fill this gap by investigating the moderating effect of IU and RNT on the relationship between perfectionism and ED symptoms, as well as the predictive power of these factors on identifying participants with clinically significant ED symptoms. 331 treatment-seeking adults from a university-affiliated community clinic and 264 undergraduate students completed measures to assess ED symptoms, RNT, perfectionism and IU. 147 participants (24.7% of the total sample) had clinically significant levels of ED symptoms as determined by the Eating Disorder Questionnaire Short-Form (EDE-QS). Multiple linear regressions found significant associations between ED symptoms and both the IU*perfectionism interaction (p < .001) and the RNT*perfectionism interaction (p < .001). A binary logistic regression identified that both the IU*perfectionism interaction (p = .03) and the RNT*perfectionism interaction (p = .001) predicted clinically significant EDE-QS scores. The findings indicate that both IU and RNT moderate the relationship between perfectionism and ED symptoms and build on previous literature recognising transdiagnostic contributors to ED symptomatology. Plain English summary Perfectionism, intolerance of uncertainty and repetitive negative thinking have been shown to maintain symptoms across multiple eating disorders. This is the first study to investigate the influence of intolerance of uncertainty and repetitive negative thinking on the relationship between perfectionism and eating disorder symptoms in a treatment-seeking sample. We found that both intolerance of uncertainty and repetitive negative thinking impact the relationship between perfectionism and eating disorder symptomatology. By better understanding the role of these constructs, we can develop more effective and personalized treatments.