Abnormality : Eating Disorders

Abnormality : Eating Disorders (13-Mar-2003)

Anorexia Nervosa (AN)

This is a behavioural disorder that is characterised by a strong desire to lose weight, resulting in a failure to eat properly. Although "anorexia" literally means "lack of appetite", anorexics do still experience hunger, but exercise severe control to minimise their food intake and lose weight. There are two types of AN:

restrictive, who achieve weight loss through fasting and physical activity
binge/purge, who occasionally overeat and then use laxatives etc., to get rid of the food they've eaten

Symptoms that are used to define a case of AN include:

distorted body image - sufferers typically overestimate their body size - e.g. when asked to manipulate an image of themselves to represent their true body size, most AN's make the image look larger than they really are
lack of insight - most AN don't believe that they have anything wrong with them
intense fear of gaining weight
preoccupation with food - while they don't eat very much, AN sufferers typically spend a lot of time thinking about food and have a ritualistic approach to its preparation

The physical consequences of anorexia include:

low weight (85% or less of typical BMI)
amenorrhea - cessation of periods
osteoparosis
dental problems, which may be aggravayed by the eroding effect of stomach acid on tooth enamel

Often, AN sufferers suffer symptoms associated with depression (lack of sleep, low mood, poor self-esteem). Most (over 90%) AN sufferers are female, although the number of male sufferers is increasing. The condition is chiefly seen in adolescence - onset is typically around 14-16 years old. Incidence of the condition appears to be increasing, with current estimates suggesting between 1-4% of all adolescents.

While 20% of AN sufferers make a full recovery from a single incidence, 20% never recover (either they are committed to care or die) and the remaining 60% make a recovery but are subject to relapses.

Bulimia Nervosa (BN)

BN has similarities to binge/purge AN, in that it is characterised by episodes of binge eating, or consuming large amounts of food, followed by self-induced vomiting. As with AN, sufferers feel dissatisfied with their body shape and have an unrealistic perception of it. However, there are some significant differences from AN, in that BN sufferers:

tend to maintain body weight rather than lose weight
have insight into their condition, and understand that they have a problem (although they are unable to exercise control over it)
less likely to suffer from depressive symptoms (not socially withdrawn)

A consequence of this is that BN sufferers are not so easily recognisable (they aren't emaciated, and still maintain a circle of friends from whom they conceal the behaviour which makes them feel guilty).

As with AN, most BN sufferers are female, although the onset occurs slightly later (e.g. early 20s). It is more frequent than AN, affecting up to 15% of adolescents.

Causes of Eating Disorders

Physiological

Holland et al (1984) (see study sheet) studied the incidence of AN and reported a concordance rate of 55% for MZ twins compared to 7% for DZ twins, which suggests a genetic basis for the condition. In a similar study on BN, Kendler et al (1993) found a concorance rate of 23% for MZ twins, which would suggest that the genetic influence is weaker, but still a factor in this condition. However, since the concordance is lower than 100%, there must be other factors at play.

Gelfand et al (1982) suggested that eating disorders may be caused by a malfunction in the hypothalamus, which known to regulate eating behaviour, and so in AN/BN may be providing inappropriate signals. However, there is no post-mortem evidence of abnormal hypothalamus in AN/BN sufferers (and even if there were, this would not prove a causative link). In any case, sufferers of AN/BN do experience hunger and use will power to suppress that urge.

Behaviourist

According to the behaviourist model, AN/BN are learnt behaviours, brought about as a result of past conditioning. In the case of eating disorders, the prevalence of an "ideal" body shape in the media leads to a fear of gaining weight, which becomes, through classical conditioning, a fear of food. Then operant conditioning ("you look good") reinforces the behaviour of the individual with the eating disorder. Given this, it should be possible using behavioural therapy to effect a cure for the conditions.

Strengths of this approach:

it offers an explanation of how the condition might arise, and why it develops and worsens
token economies ("gold star award" approach) have been shown to be successful in the treatment of eating disorders

Weaknesses:

doesn't explain why it affects adolescents more than any other group
anorexics who are very thin are encouraged to eat, and therefore are not getting reinforcement for their behaviour

Cognitive Behavioural

Here the emphasis is on the individual's perception of themselves and the world, and so suggests that the media has an important part to play in creating the impression that "slim is good". This appears to be borne out by the example of Fiji, where eating disorders were virtually unknown until 1995, when TV was introduced. Within three years, 74% of teenage girls reported feeling that they were "too fat". Garner et al (1980) found that Playboy centrefold models have become progressively thinner since 1960, although the average weight of females has risen during the same period.

Strengths of this approach:

it explains why eating disorders are predominantly associated with women
backed up by the experience of Fiji

Weaknesses:

Doesn't explain why not everyone has an eating disorder, even though everyone is exposed to the same media pressures

Psychodynamic

There are several explanations based on the psychodynamic approach: one suggests that AN sufferers fear adulthood, and therefore don't eat as a way of avoiding puberty (the development of breasts, menstruation), or because they unconsciously associate being fat with being pregnant.

An alternative explanation suggests that the family structure is a major factor in the development of eating disorders, and identifies some factors commonly found in anorexic children:

they are co-operative and well behaved
they tend to do well at school
they have domineering parents

Bruch (1991) suggests that anorexics use their condition as a way of gaining some level of control over their lives, which are otherwise strictly organised by their parents.

Minuchen (1978) suggests that AN is a result of dysfunctional family systems, and that the anorexic is unconsciously using her condition as a way of manipulating the family dynamic. For example, if the parents argue, then the child might be able to unite them in a concern for her well-being.

Diathesis/Stress

This model suggests that eating disorders occur in individuals who have both a genetic predisposition, and who experience certain environmental influences. (diathesis==inherited propensity).

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