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/m(2), 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.