## Core Concept
Anorexia nervosa is a psychological eating disorder characterized by an intense fear of gaining weight and a distorted body image, leading to restricted food intake and significant weight loss. The diagnostic criteria for anorexia nervosa include specific behavioral and physical characteristics. The duration criterion is crucial for diagnosing the disorder.

## Why the Correct Answer is Right
The correct answer, , indicates that the duration criterion for anorexia nervosa is at least 3 months. This criterion is part of the diagnostic requirements outlined in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition). For a diagnosis of anorexia nervosa, the individual must exhibit a significant and persistent reduction in food intake leading to extremely low body weight, an intense fear of gaining weight or becoming fat, and a disturbance in the way one's body weight or shape is experienced. The 3-month duration criterion helps distinguish between transient dietary restrictions and a persistent, pathological eating pattern.

## Why Each Wrong Option is Incorrect
* **Option A:** is incorrect because it does not accurately reflect the specified duration criterion for diagnosing anorexia nervosa.
* **Option B:** is incorrect because, similar to option A, it does not match the established duration requirement.
* **Option D:** is incorrect as it suggests a longer duration than what is required for the diagnosis.

## Clinical Pearl / High-Yield Fact
A key clinical pearl for anorexia nervosa is that the disorder can have serious physical health consequences, including osteoporosis, heart problems, and gastrointestinal issues, in addition to its psychological effects. Early recognition and treatment are crucial. A helpful mnemonic to remember some of the diagnostic features is "Fear, Food, and Famished," reflecting the fear of gaining weight, the restriction of food intake, and the resultant famished state.

## Correct Answer: B. 3 months.