ICD-10 Classification of Mental and Behavioural Disorders, World Health Organization, Geneva, 1992
Definition | Diagnostic Guidelines | DCR-10 Criteria
Anorexia nervosa is a disorder characterized by deliberate weight loss, induced and/or sustained by the patient. The disorder occurs most commonly in adolescent girls and young women, but adolescent boys and young men may be affected more rarely, as may children approaching puberty and older women up to the menopause. Anorexia nervosa constitutes an independent syndrome in the following sense: 1. the clinical features of the syndrome are easily recognized, so that diagnosis
is reliable with a high level of agreement between clinicians;
2. follow-up studies have shown that, among patients who do not recover, a
considerable number continue to show the same main features of anorexia nervosa,
in a chronic form.
Although the fundamental causes of anorexia nervosa remain elusive, there is growing evidence that interacting sociocultural and biological factors contribute to its causation, as do less specific psychological mechanism and a vulnerability of personality. The disorder is associated with undernutrition of varying severity, with resulting secondary endocrine and metabolic changes and disturbances of bodily function. There remains some doubt as to whether the characteristic endocrine disorder is entirely due to the undernutrition and the direct effect of various behaviours that have brought it about (e.g. restricted dietary choice, excessive exercise and alterations in body composition, induced vomiting and purgation and the consequent electrolyte disturbances), or whether uncertain factors are also involved.
For a definite diagnosis, all the following are required:
1. Body weight is maintained at least 15% below that expected (either lost
or never achieved), or Quetelet's body-mass index is 17.5 or less. Prepubertal
patients may show failure to make the expected weight gain during the period
of growth.
2. The weight loss is self-induced by avoidance of "fattening foods" and
one or more of the following: self-induced vomiting; self-induced purging;
excessive exercise; use of appetite suppressants and/or diuretics.
3. There is body-image distortion in the form of a specific psychopathology
whereby a dread of fatness persists as an intrusive, overvalued idea and the
patient imposes a low weight threshold on himself or herself.
4. A widespread endocrine disorder involving the hypothalamic-pituitary-gonadal
axis is manifest in women as amenorrhoea and in men as a loss of sexual interest
and potency. (An apparent exception is the persistence of vaginal bleeds in
anorexic women who are receiving replacement hormonal therapy, most commonly
taken as a contraceptive pill.) There may also be elevated levels of growth
hormone, raised levels of cortisol, changes in the peripheral metabolism of
the thyroid hormone, and abnormalities of insulin secretion.
5. If onset is prepubertal, the sequence of pubertal events is delayed or even
arrested (growth ceases; in girls the breasts do not develop and there is a
primary amenorrhoea; in boys the genitals remain juvenile). With recovery,
puberty is often completed normally, but the menarche is late.
Differential Diagnosis:
There may be associated depressive or obsessional symptoms, as well as features of a personality disorder, which may make differentiation difficult and/or require the use of more than one diagnostic code. Somatic causes of weight loss in young patients that must be distinguished include chronic debilitating diseases, brain tumors, and intestinal disorders such as Crohn's disease or a malabsorption syndrome.
A. There is weight loss or, in children, a lack of weight gain, leading
to a body weight of at least 15 % below the normal or expected weight for
age and height
B. The weight loss is self-induced by avoidance of 'fattening foods'
C. There is self-perception of being too fat, with an intrusive fear of fatness,
which leads to a self-imposed low weight threshold
D. A widespread endocrine disorder involving the hypothalamic-pituitary-gonadal
axis is manifest in women as amenorrhoea, and in men as a loss of sexual interest
and potency
E. The disorder does not meet criteria A and B for bulimia nervosa
ICD-10 copyright © 1992 by World Health Organization.