Symptomatology and diagnostic criteria
Preocupation with body weight and shape.
Body image is usually distored in a way that, even though, the actual body weight may
be dangerously low, patients percieve themselves as overweight or have fears of
Bulimia nervosa (BN) shares several symptoms with AN however in BN, patients
usually have normal body weight and frequent episodes of binge-eating, during which
they consume large amounts of food.
Both BN and AN can be subdivided according to the presence or absence of
compensatory behaviours (‘purging’), which include excessive exercising, deloberate
vomiting, or use of laxatives or diuretics.
Patients with eating disorders often have difficulties in recognizing their own emotional
states, which has been referred to as ‘alexithymia.’
In developed countries, AN has a lifetime prevelance of about 1%, and BN being twice as
common in the general population.
AN is the third most common chronix disorder is adolescent girls in Western countries.
For example, in the USA as many as 5% to 15% of adolescent girls control their body
weight by making use of purging behaviours. AN and BN in males is exceptionally rare, a
total of about 90% to 98% of affected individuals are female.
The typical age of onset is around puberty for AN and late adolescence for BN.
Environmental risk factors
Research into attachment has shown that patients with eating disorders frequently
report poor parental care. Specifically, fathers of patients with eating disorders are
often described as unavailable, whereas mothers are described as overprotective and
dominant with a tendency towards perfectionism.
Childhood sexual abuse has been identified as a non-specific risk factor for eating
disorders. Traumatic experiences increase the risk for comorbid disorders and
subclinical post-traumatic stress disorders may be a risk factor for BN.
Adolescent girls and young women are particularly vulnerable to developing AN or BN
if they come from a high-income and high-education background and have difficulties in
accepting traditional role models.
Evolutionary synthesis Eating disorders comprise phenotypically diverse manifestations of problems with the
regulation of food intake and body weight. AN and BN are associated with a strong
desire to gain control over pressure to fulfil socio-biological role models.
From an evolutionary perspective, the prevelance of eating disorders presents a
1. There is an inverse relationship between food availibility and prevelance of
eating disorders across societies.
2. Irregularities of the menstrual cycle or amenorrhoea, which frequently occur in
eating disorders, counteract any reproductive effort.
Studies suggest that mothers of adolescent girls with AN tend to be overprotective,
dominating and monopolizing. Patients with AN, on the other hand, are often
overcomplaiant, and worry excessively about the wellbeing of the family.
AN is also associated with low self-esteem, introversion, pronounced harm avoidance
and reduced novelty seeking, and the co-occurence with anxiety disorders and
depression suggests that patients with eating disorders unconciously assume the
behavioural strategy of a subordinate individual to which genes may contribute
Elevated stress level in subordinates, for example, are known to contribute to the
suppression of ovulation, and such a scenario is similarly conceivable in humans.
Women may also suppress the reproductive potential of other women by cultural
means, for instance, by unconciously promoting that the ‘ideal’ female figure is one of
below average weight.
As youth signals attractiveness, there is intrasexual competition in women for looking
thin, which may, to some extent, enhance the preference for thinness not only by men
but also women.
In some cases, it may even be possible that suppressed reproduction is not due to the
interference of an unrelated higher-ranking female, but that the mother of the affected
adolescent girl is the source of manipulation.
Alturistic behaviour of adolescent girls may be imposed upon the daughter by her
mother, particularly in the presence of (male) siblings.
Another reason for mothers (and fathers) to suppress fertility in adolescent daughters.
The abundance of nutrient-right