Purging frequency and number of purging methods as indicators of severity in bulimia nervosa: Interactive effects with binge eating episodes.

Objective: In the Diagnostic and Statistical Manual of Mental Disorders-5, severity of bulimia nervosa (BN) is defined by the frequency of purging behaviour. Previous research suggests the number of purging methods as an alternative rating. The current analysis investigated characteristics (sociodemographic and treatment-related variables, body mass index [BMI], eating disorder-specific and general psychopathology) of persons with BN as a function of purging frequency and number of purging methods in order to examine which approach might be better suited for indicating severity of BN.

Method: Two-hundred and sixty-one persons (98.5% female; mean age 25.2 years, SD = 9.41; mean BMI 22.0 kg/m², SD = 3.79) with BN completed self-report questionnaires on eating disorder-specific and general psychopathology at admission to inpatient (n = 214) or daypatient (n = 47) treatment.

Results: Higher severity based on either purging frequency or number of purging methods tended to relate to lower BMI and higher eating disorder-specific and general psychopathology. In addition, binge-eating frequency differentially related to eating disorder-specific and general psychopathology as a function of severity groups.

Conclusions: This study partially supports the utility of both purging frequency and the number of purging methods as indicators of severity in persons with BN. However, focussing only on purging behaviours may be short-sighted as it appears necessary to consider the number of binge-eating episodes as well when evaluating severity of BN.