Eating Disorders

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  • Created on: 06-01-13 16:10

Characteristics of Anorexia Nervosa

Weight: Less than 85% below normal body weight, refusal to maintain expected weight

Anxiety / Eating Behaviour: Failure to lose weight can lead to anxiety, restrict calorie intake to 600-800 a day

Body Perception: Distorted – see themselves as overweight when they are actually too thin

Major Physical Symptoms/effects: Dry skin, dehydration, malnutrition, brittle nails, thinning hair, amenorrhea (periods stop), and fine hair growth on body

Gender: Estimated 90-95% are female. Therefore 5-10% are male

Age of onset: 90% of severe cases start between 12-18 years, though there are cases as young as 8 years

Other: Up to 5-20% die due to starvation or suicide (highest mortality rate of any mental disorder) Compulsive and excessive exercise. Use of laxatives, secretive disorders

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Genetic Explanation

The genetic explanation for Anorexia suggests that people inherit the tendency to develop this disorder. 

We know that Anorexia affects approximately 0.5% - 1% of the population. This means that any individual has a 0.5 – 1% chance of developing the disorder. When looking at families, where at least one relative has the disorder, there is a 4 – 5% chance of other relatives also developing the disorder.

This supports the genetic argument because…

It argues that it is passed through the genes of the biological parents HOWEVER! Could be just social learning theory – watching your family do this. Also, not a high percentage so not definite

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Holland et al (1984)

Aim: to investigate whether people inherited a genetic vulnerability to anorexia.

Procedure: Followed up women who were diagnosed as anorexic and had a twin. They found 30 female twin pairs (16 MZ and 14 DZ), 4 male twin pairs and one set of triplets.

They looked at medical records and interviewed each twin. Where the second twin had anorexia (or had ever had it), the twin pair was classed as concordant. Where the second twin had never had anorexia, the pair was classed as discordant.


  • 55% of the monozygotic twins were concordant
  • 7% of the dizygotic twins were concordant
  • Also, in 5 cases where the other female twin did not have anorexia they either had a minor eating disorder or psychiatric illness


Suggests that genetic factors must play a role because concordance rates are much higher for MZ twins than for DZ twins. It is also much higher than the national average (0.5 – 1%).

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  • Although not 100%, the concordance rate is more than half and still quite high compared to DZ twins


  • Not 100% so not definite, there are other factors at play
  • Small sample, ] not representative
  • Social disarability bias; may not want them to know they’re anorexic
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Neurological Explanation

The neurotransmitter serotonin may be linked to AN.  It has also been linked to depression and OCD.  Studies from 5 years ago seemed to suggest that serotonin levels were low in suffers of AN, but most studies were on people with the disorder already.  

It has been shown that extreme body weight loss can produce hormonal and brain changes as the body is trying to cope.

PET (positron emissions test) scans of the brain have shown that there are fewer serotonin receptors in the brains of people with eating disorders (Kaye et al, 2005).  They also showed that these changes are present in people who have recovered. 

Serotonin has been linked to the following characteristics – perfectionism, anxiety, depression and obsessionality.  It is also linked to the feeding centre of the brain, the hypothalamus.

  • Can’t establish cause and effect; serotonin and AN
  • The low level of receptors could be a long term complication of the illness
  • The only way to prove would be to show the difference there is before illness onset- very difficult with such a rare disorder
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Evolutionary Explanation

This theory would say that anorexic behaviour must have some benefit for survival of a species; otherwise it would not be passed down between generations. 

Adapted to flee famine hypothesis (AFFH) (Guisinger, 2003)

 This theory suggests that anorexic behaviour were adaptive one or two million years ago.  At that time hunter-gatherers needed to move to where the food supplies were (i.e. nomadic).  People with AN tend to be restless and show high levels of activity, but most people when starved become inactive and depressed.  She then hypothesised that high activity levels and denial of hunger would help someone to migrate in response to famine in their area.

(in order to get to somewhere where there is an abundance of food, they need to cope with starvation)

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Evaluation of Evolutionary Theory


  • It has been suggested though that having the occasional person who behaved like this would be beneficial for the group – more for everyone else.  This is inclusive fitness – benefits the group not the individual.  
  • The person’s relatives would benefit and that means the genes would be passed on.  


  • There is no direct evidence for this and it does not explain why mainly females suffer from it
  • Anyone who was part of a hunter-gatherer group who chose to refuse food when it was available would weaken and die early on, not adaptive
  • Reductionist – simplifies a complex behaviour
  • Determinist – ignores free will
  • Nature/Nurture –ignores social and external forces influencing behaviour
  • Gender bias – most research is carried out on women
  • Unfalsifiable – can’t test it
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Psychodynamic Explanations

Control – Bruch (1973)

  • Anorexics struggle to be independent from their parents
  • Controlling their eating is one area they are able to control
  • This increases their self efficacy (beliefs in own skills/abilities)
  • Helps them to feel autonomous (self sufficient)
  • Anorexics are often ‘good girls’ – do well at school, are cooperative and well behaved. As a result they may feel they’re controlled by others

Remain pre-pubescent / pre-pubertal – Crisp (1980)

  • Anorexia is an attempt to remain pre-pubescent in order to prevent/postpone adulthood (unconscious desire)
  • This is because they are over dependent on their parents and may therefore fear becoming independent and sexually mature
  • Consequently anorexia prevents periods, decreases body weight etc, physically they return to a child like state
  • This also helps them avoid the possibility of pregnancy which is associated with adulthood
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Family Systems – Minuchin et al (1978)

  • Anorexia diverts attention away from other family problems for example relationship problems
  • The assumption is that if the attention is focussed on the anorexic child this may help keep the family together – may bring the parents closer together
  • May split parents apart
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Evaluation of Psychodynamic Explanation


  • A lot of in depth information can be collected from a case study
  • Treatments based on this assumption are effective
  • This explanation provides a complex explanation of behaviour, considering a diverse range of causes for behaviour and is therefore not reductionist (family, past experience and control)
  • explains why females are more likely to suffer from it, by not eating they reduce the size of breasts, their periods stop: they are more likely to look like a child


  • Psychology as a science - Unfalsifiable – cannot test it
  • Nature/nurture:  your experiences are affecting your behaviour, no explanation of biology etc
  • Determinist – too deterministic, ignores free will
  • Doesn’t help us to understand why males develop the disorder
  • Are family problems a cause or effect of the disorder?
  • All these theories are based on case studies – these are hard to generalise as they are a restricted sample
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Behaviourist Theories

Operant Conditioning

ED’s are learned behaviours and behaviour is maintained through positive reinforcement e.g. a diet that is successful is rewarding and others make positive comments. Positive reinforcement encourages behaviour to be repeated. Restricting eating may begin as slimming; however an anorexic takes it too far.

Social Learning (role models)

The mass media portrays the female body shape in a particular way. This may also contribute to the development of anorexia.





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Barlow & Durand (1995) – ‘Miss America’ contestants

Found that over 50% of contestants were about 15% below their normal body weight. They also found that there had been a decrease in average weight over the last 30 years. This shows that the ideal size is now seen as slim

Lee (1992) – China

Found that eating disorders are rare in China because dieting is not part of the Chinese culture and thinness is seen as a sign of ill-health - plus wasting food is seen as unlucky.

However, Chinese doctors may not report eating disorders because they are not familiar to them. 

Hoek  - (1998)

Found cases of anorexia after searching medical records on a Caribbean island (Curacao) where 'fat is beautiful'. These cases had not been reported because they were not expected.

All role models are fat – so why are there still cases of anorexia?

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Evaluation of the Behaviourist Explanation


  • Strong case for the persistence of anorexia (craving rewards like going on the scales and seeing youve lost weight)
  • Role modelling does help us understand why there’s been an increase in number of cases in recent years. Also may explain why female cases are far more common


  • Does not explain why many women diet and are subject to media influences but do not develop anorexia
  • Does not explain why many anorexics continue to diet even when compliments (positive reinforcements stop)
  • Reductionism: uses a simplified explanation to explain a complex behaviour
  • Deterministic: ignores free will
  • focuses on environmental factors and ignores biological ones
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