Whether a person can be diagnosed with both Anorexia Nervosa (AN) and Bulimia Nervosa (BN) simultaneously is a common source of confusion. While many emotional and behavioral traits overlap, the medical and psychiatric communities use specific criteria to distinguish them. Diagnostic guidelines, established in the Diagnostic and Statistical Manual of Mental Disorders (DSM), create a hierarchy that prevents the official co-diagnosis of full-syndrome AN and BN at the same time. The distinction rests primarily on one physical health factor: the individual’s body weight.
Understanding Anorexia Nervosa
Anorexia Nervosa (AN) is characterized by a persistent restriction of energy intake, leading to a significantly low body weight relative to a person’s age, sex, and physical health. This low body weight is the defining feature of the disorder and is considered a state of starvation that affects nearly every organ system. The second characteristic is an intense fear of gaining weight or exhibiting persistent behavior that interferes with weight gain, even while at a significantly low weight. Individuals with AN also experience a disturbance in how they perceive their body shape or weight, often linking their self-worth to their body size.
Subtypes of Anorexia Nervosa
The clinical definition of AN includes two specific subtypes, differentiated based on the individual’s behaviors over the past three months.
Restricting Type
The Restricting Type achieves weight loss primarily through dieting, fasting, and/or excessive exercise, without engaging in recurrent episodes of binge eating or purging.
Binge-Eating/Purging Type
The Binge-Eating/Purging Type describes individuals who meet the low-weight criteria for AN but have engaged in recurrent episodes of binge eating or purging behavior. Purging behaviors can include self-induced vomiting or the misuse of laxatives, diuretics, or enemas.
Understanding Bulimia Nervosa
Bulimia Nervosa (BN) is defined by a pattern of recurrent episodes of binge eating, followed by inappropriate compensatory behaviors aimed at preventing weight gain. A binge-eating episode involves consuming an amount of food that is definitely larger than most people would eat in a similar period, coupled with a sense of lack of control over eating during the episode. The compensatory behaviors may include self-induced vomiting, misuse of laxatives or diuretics, fasting, or excessive exercise.
For a diagnosis of BN, these bingeing and compensatory behaviors must occur, on average, at least once a week for three months. A person with BN also bases their self-evaluation unduly on their body shape and weight. A significant distinction from AN is that the diagnosis of BN is made regardless of the individual’s weight, provided they are not currently at a significantly low body weight. Individuals with BN are typically at a normal weight or may be overweight, which separates the disorder from AN.
Why Simultaneous Diagnosis Is Not Used
The reason a person cannot be officially diagnosed with both Anorexia Nervosa and Bulimia Nervosa at the same time lies in the specific hierarchical rule used by the DSM. This system places the diagnosis of AN above that of BN. The defining point of this hierarchy is the individual’s current body weight status.
If an individual meets all the criteria for Anorexia Nervosa, including the requirement of having a significantly low body weight, the diagnosis of Bulimia Nervosa is automatically excluded. This exclusion applies even if the person engages in frequent bingeing and purging behaviors. In such a scenario, the individual receives the diagnosis of Anorexia Nervosa, Binge-Eating/Purging Type.
The clinical rationale for this rule is that the state of low body weight in AN represents a more severe, life-threatening medical condition that takes diagnostic precedence. The physiological dangers associated with starvation, such as heart failure, electrolyte imbalances, and organ damage, are often more immediate and severe than those typically seen in BN.
If a person engages in the full pattern of bingeing and compensatory behaviors but does not meet the criterion for significantly low body weight, they are then diagnosed with Bulimia Nervosa. This distinction highlights that the underlying diagnosis is determined by the severity of the individual’s nutritional status. The DSM framework ensures that the most clinically severe condition is recognized first, guiding the immediate focus of medical treatment.
Recognizing Signs and Seeking Support
Recognizing the signs of an eating disorder in yourself or a loved one is the first step toward professional help, regardless of the specific diagnosis. Warning signs often include a preoccupation with body weight, shape, or size, and a refusal to eat certain foods or food groups. Sudden or drastic weight changes should be taken seriously as a potential indicator of a problem.
Behavioral changes like withdrawing from social activities, especially those involving food, or developing secretive eating habits may signal a disorder. Other physical and behavioral indicators include frequent trips to the bathroom after meals, compulsive exercise that interferes with other activities, and noticeable mood shifts.
Any suspicion of an eating disorder warrants a professional assessment due to the complexity and potential medical severity of these conditions. A qualified mental health professional, such as a psychiatrist or specialized eating disorder therapist, is needed for an accurate diagnosis and to create a tailored treatment plan. Early intervention significantly improves the chances for a full recovery.