Assessing severity in anorexia nervosa: Do the DSM‐5 and an alternative severity rating based on overvaluation of weight and shape severity differ in psychological and biological correlates?

Objective This study evaluated the severity ratings for anorexia nervosa (AN) in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM‐5) and an alternative severity rating based on overvaluation of weight/shape, on a range of psychological and biological variables. Method A sample of 312 treatment‐seeking patients with AN (mean age = 25.3, SD = 7.6; mean BMI = 16.8 kg/m2, SD = 2.4) were categorised using both DSM‐5 severity levels (mild/moderate/severe/extreme) and weight/shape (low/high) overvaluation. The severity categories were compared on a range of psychological (e.g., eating psychopathology) and biological (e.g., sodium) variables. Results Results showed that the overvaluation of weight/shape appeared better at indexing the level of severity in psychological variables among patients with AN compared to the DSM‐5 severity rating with moderate to large effect sizes. Moreover, the DSM‐5 mild and moderate severity groups experienced significantly higher eating and general psychopathology than the severe and extreme groups. Finally, neither the DSM‐5 nor the weight/shape severity groups differed on any of the biological variables. Conclusions This study provided no support for the DSM‐5 severity rating for AN, while initial support was found for the weight/shape overvaluation approach in indexing psychological but not biological correlates. Highlights This study assessed both the Diagnostic and Statistical Manual of Mental Disorders‐5 (DSM‐5) and the alternative severity indices for anorexia nervosa (AN) using overvaluation of weight and shape on a range of psychological (e.g., eating psychopathology) and biological (e.g., sodium, potassium level) correlates. Overvaluation of weight/shape appeared to be better at indexing the level of severity in psychological variables among patients with AN compared to the DSM‐5 severity rating with moderate to large effect sizes. Neither the DSM‐5 nor the weight/shape severity groups were able to index the level of severity in biological variables.