Anorexia nervosa is a psychiatric diagnosis that describes an eating disorder, characterized by low body weight and body image distortion, with an obsessive fear of gaining weight. Individuals with anorexia are known to control body weight commonly through the means of voluntary starvation, purging, vomiting, excessive exercise or other weight control measures, such as diet pills or diuretic drugs. While the condition primarily affects adolescent females, approximately 10% of people with the diagnosis are male. Anorexia nervosa, involving neurobiological, psychological, and sociological componentsLask B, and Bryant-Waugh, R (eds) (2000) Anorexia Nervosa and Related Eating Disorders in Childhood and Adolescence. Hove: Psychology Press. ISBN 0-86377-804-6., is a complex condition that can lead to death in severe cases.

The term anorexia is of Greek origin: a (α, prefix of negation), n (ν, link between two vowels) and orexis (ορεξις, appetite), thus meaning a lack of desire to eat.

"Anorexia nervosa" is frequently shortened to "anorexia" in the popular media. This is technically incorrect, as the term "anorexia" used separately refers to the medical symptom of reduced appetite (which therefore is distinguishable from anorexia nervosa in being non-psychiatric).

Diagnosis and clinical features

The most commonly used criteria for diagnosing anorexia are established by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) and the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD).

Although biological tests can aid the diagnosis of anorexia, the diagnosis is based on a combination of behavior, reported beliefs and experiences, and physical characteristics of the patient. Anorexia is typically diagnosed by a clinical psychologist, psychiatrist or other suitably qualified clinician. Notably, diagnostic criteria are intended to assist clinicians, and are not intended to be representative of what an individual sufferer feels or experiences in living with the illness.

The full ICD-10 diagnostic criteria for anorexia nervosa can be found here, and the DSM-IV-TR criteria can be found here.

To be diagnosed as having anorexia nervosa, according to the DSM-IV-TR, a person must display:

1. Refusal to maintain body weight at or above a minimally normal weight for age and height (e.g., weight loss leading to maintenance of body weight less than 85% of that expected; or failure to make expected weight gain during period of growth, leading to body weight less than 85% of that expected).
2. Intense fear of gaining weight or becoming obese
3. Disturbance in the way in which one's body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or denial of the seriousness of the current low body weight.
4. The absence of at least three consecutive menstrual cycles (amenorrhea) in women who have had their first menstrual period but have not yet gone through menopause (postmenarcheal, premenopausal females).