AN and BN are serious mental health conditions defined by specific patterns of disordered eating and body image distress. Both disorders involve harmful behaviors like restriction, bingeing, or purging, which severely impact physical and psychological health. The possibility of having both conditions simultaneously is often misunderstood due to the overlap in behaviors. Understanding the precise distinctions established by clinical diagnostic manuals is necessary to address this question accurately.
The Core Diagnostic Rule
The answer to whether one can be simultaneously diagnosed with Anorexia Nervosa and Bulimia Nervosa is technically no, based on current psychiatric classification systems like the DSM-5. This mutual exclusivity is defined by a single factor: the individual’s weight status. Anorexia Nervosa requires restriction of energy intake leading to a significantly low body weight, defined as less than minimally normal for the individual’s age, sex, and physical health.
Bulimia Nervosa includes an exclusion criterion stating that the disturbance does not occur exclusively during episodes of Anorexia Nervosa. If an individual engages in recurrent binge eating and compensatory behaviors but their body weight is significantly low, the primary diagnosis must default to Anorexia Nervosa. The weight status serves as the definitive boundary preventing the simultaneous assignment of both diagnoses.
Anorexia Nervosa Binge-Purge Type
The overlap in behaviors is accounted for by a specific subtype of Anorexia Nervosa. AN is divided into two primary subtypes: the Restricting Type and the Binge-Eating/Purging Type. An individual is classified as having the AN Binge-Purge Type if they maintain a significantly low body weight and engage in recurrent episodes of binge eating or purging behaviors, such as self-induced vomiting or misuse of laxatives, within the last three months.
The behaviors of bingeing and purging are present in both the AN Binge-Purge Type and Bulimia Nervosa, but the underlying weight status dictates the diagnosis. In the AN Binge-Purge Type, the restriction resulting in a significantly low body weight is the overriding feature. The bingeing and purging behaviors are secondary to the core criterion of being underweight, which separates this AN subtype from a diagnosis of Bulimia Nervosa.
Navigating Diagnostic Crossover
While a simultaneous diagnosis is not possible, individuals commonly experience a shift, or “crossover,” between these diagnostic categories over time. Eating disorders are not static conditions, and a patient’s primary diagnosis may change as symptoms and body weight fluctuate. This diagnostic fluidity is a well-documented aspect of the illness course.
For example, a person initially diagnosed with the Restricting Type of Anorexia Nervosa may begin engaging in bingeing and purging behaviors while remaining underweight, leading to a change to the AN Binge-Purge Type. If that individual restores their weight to a minimally normal range but continues the cycle of binge eating and compensatory behaviors, their diagnosis would then shift to Bulimia Nervosa. Research suggests that 20% to 50% of individuals initially diagnosed with Anorexia Nervosa eventually develop Bulimia Nervosa over time.
Treatment Implications of Precise Diagnosis
These precise diagnostic distinctions, particularly weight status, are relevant for medical professionals because they directly inform immediate treatment priorities. For a patient with Anorexia Nervosa, regardless of the subtype, the significantly low body weight creates immediate, life-threatening medical risks, including cardiac complications and severe malnutrition. Therefore, the initial focus of treatment must be medical stabilization and weight restoration.
For a patient with Bulimia Nervosa, who is at or above a minimally normal weight, the immediate medical risk often centers on severe electrolyte imbalances caused by frequent purging, which can lead to dangerous cardiac issues. The distinction guides the initial therapeutic strategy, determining whether the focus is first on refeeding and weight gain (as in AN), or on interrupting the binge-purge cycle and addressing associated medical complications (as in BN). This clear classification ensures that the most pressing medical and psychological needs are addressed effectively.