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Psychology for AS

Critical Issue : Eating Disorders

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Clinical Characteristics of Anorexia Nervosa
  • Refusal to maintain expected body weight (below 85% of normal, only 600-800 calories eaten per day).
  • Distorted body image.
  • Preoccupation with food (thinkabout, dream about, read about, and make food, but wont eat it).
  • Cessation of menstruation (absence of 3 or more).
  • Include depression.
  • They rarely admit they have a problem.

Clinical Characteristics of Bulimia Nervosa

  • Binge eating (feel extreme tension, relieved by eating lots of high calorie food).
  • Compensatory behaviour (binge followed by guilt - purge by vomiting, laxatives, enemas or excessive exercise).
  • Maintenance of normal body weight (vomiting removes only half of the calories consumed - bulimia difficult to spot because bulimics can maintain normal body weight and even be overweight).



The idea that we have a gene for anorexia and bulimia.

Genetic science not been able to find a gene.

Research has focused on whether disorders run in families.

Twin studies; we would expect to see more Monozygotic twins both having the disorder that Dizygotic twins. Both twins usually share same environment. Only difference between Mz and Dz twins is their degree of genetic similarity. Concordance rates are looked at in twin studies.

Holland et al. Study of genetic vulnerability in ANOREXICS

Aims To investigate whether there was a higher concordance rate of anorexia nervosa for Mz than Dz twins.

Proc 34 pairs of twins (30 female and 4 male). 1 set of triplets. Natural experiment - IV (genetic relatedness) cannot be controlled. Physical resemblance questionnaire established whether the twins were Mz (16 pairs) or Dz (14 pairs). If there was any uncertainty a blood test was carried out. Longitudinal study - over time. Clinical interview and standard criteria used to diagnose anorexia.

Find Significant difference - much higher concordance rate for Mz (56%) than Dz (7%) twins. Further findings - in 3 cases where the non-diagnoses twin did not have anorexia, they were diagnosed with other mental illnesses, and 2 had minor eating disorders.

Conc Genetic basis for Anorexia suggested. Genes not wholly responsible, constitute a pre-disposition. Individual vulnerable but the disorder is not triggered. Implications include the need to identify precipitating factors ie, environmental triggers.

Crit (1) The higher concordance rate for Mz twins may be due to being brought up in a more similar environment than Dz twins. It is difficult to tell whether concordance is due to genes or environment.   (2) The sample is too small, so it might be unrepresentative of otheres with anorexia.

Kendler et al. Study of genetic vulnerability in BULIMICS

Aims To investigate whether there was a higher concordance rate of bulimia nervosa for Mz than Dz twins.

Proc 2163 female twins - 1 of the pair having bulimia. Natural experiment - IV (genetic relatedness) cannot be controlled. Longitudinal study - over time. Clinical interview and standard criteria used to diagnose bulimia.

Find Higher concordance rate for Mz (23%) than Dz (9%) twins. 123 cases of bulimia reported. Significant evidence of other mental disorders also reported : 10% of non-bulimic twins had anorexia, 5% a phobia, and, 11% an anxiety disorder.

Conc [See Holland study but change anorexia to bulimia]

Crit (1) [see Holland crit 1].   (2) Bigger sample size so the results are more representative.

Criticisms of Genetic explanations of eating disorders

+ Genetic factors do play a part.

- Other factors, not just genes, must play a part because concordance rates for Mz twins would have been 100% if purely genetic.

- Mz twins could have been treated more similarly than Dz twins.

Biochemical (Bulimia only)

Bulimia has been associated with low levels of serotonin - eating lareg amounts of starchy foods containing carbohydrates can increase serotonin levels in the brain, and this may improce mood in individuals with low serotonin levels.


+ extra serotonin could decrease the amount of binging.

- Bulimics don't just focus on carbohydrates, they eat anything.

- Cause and effect. Could be disorder causing neurotransmitter levels and not neurotransmitter levels causing disorder.


Individuals with eating disorders may have brain abnormalities. Research focused on HYPOTHALAMUS. Studies of rats have found that when the lateral hypothalamus is stimulated electrically, the rat eats. If it is destroyed, the rat refuses to eat. A malfunction of this part of the hypothalamus offers a possible explanation for eating disorders.


- Cannot generalise studies from rats to humans.

- In humans, altered hypothalamus activity may not be a cause of weight loss but occur as a result.

- Post-mortems of anorexics have not revealed any damage to this area of the brain.

**Evaluation of Biological Explanations**

Nature side, of nature/nurture debate, emphasised.

Biological causes emphasised, either having a gene or a problem with the brain or body's chemical balance.



unresolved problems at oral stage of development.

excessive pleasure = oral receptive personality (very trusting and dependent on others). frightened of becoming sexually mature in puberty.

not enough pleasure = oral aggressive personality (controlling and dominating). anorexic feels they have no independence and no control, use not eating and controlling weight to gain control.


- Relies on abstract concepts - unconscious mind. Cannot be directly observed or measured. Seems contradictory as it cannot be proved wrong. It is a bad theory.

+ Childhood experiences can affect adult behaviour, some evidence linking early traumatic experience with eating disorders in later life. McLelland et al reported that 30% of clients with eating disorders had a history of sexual abuse.

- Does not explain with anorexia sometimes begins after adolescence.


1. Conditioning theory

Anorexia is 'slimming got out of hand'.

Operant and classical conditioning used to explain anorexia.

Person loses weight and receives praise from others and so feels good. Anorexic links not eating with feeling good and continues to diet.


- A lot of people diet but not everyone becomes anorexic.

- A person at any age could diet and so this explanation does not explain why eating disorders tend to be during adolescence.

- Not very good at explaining bulimia as bingeing and purging are done in secret and so are not reinforced.

2. Social learning theory

Western society - beauty in women associated with looking slim.

Most models are medically underweight.

Teenage girls learn to be accepted as attractive, there is a need to be slim. This can lead to anorexia.

Girls who most identify with these models are most likely to get anorexia.


Lee et al reported that anorexia and bulimia remain very rare among the chinese. Fatness is valued. The greeting "you have gained weight" is a compliment. Chinese don't eat same amount of fatty foods as in western society.

Behar at al. study of a psychological explanation for bulimia and anorexia

Aims To investigate the effect of gender identity on eating disorders.

Proc 126 p's (63 patients, 63 control). Natural experiment - IV (having a feminine gender identity) cannot be controlled. Structured clinical interview for diagnosis using standard criteria. Self-report survey to measure gender identity.

Find More patients were classified with feminine gender identity (43% compared to 23.8% of controls). More controls classified as androgynous (31.7% compared to 19% of patients). More controls classified as undifferentiated (43% compared to 27% patients).

Conc Feminine gender identity more prevalent in patients than controls - supports behavioural explanation. Positive applications of androgyny implied as a defence against eating disorders.

Crit (1) Natural experiment - IV not under control of experimenter. Cause and effect not clear - eating disorder could cause feminine gender identity.  (2) Study ignores the role nature might play in causing eating disorders.

Criticisms of social learning!!!

+ Good looks in boys less associated with being slim - explains why fewer boys get eating disorders.

+ 50s ideal = full figure. Now = thinness. Rise in eating disorders. Also male role models are getting thinner and this correlates with rise in eating disorders in males.

- All women suffer the same pressures from media but most don't get eating disorders. This suggests that social learning theory is not only reason for eating disorders. It is only those young women who are already vulnerable who are likely to get eating disorders.


Behavioural explanations of eating disorders are criticised because not every girl who is subjected to scoial pressure to be thin actually becomes anorexic. Cognitive theories argue that those girls who do develop eating disorders are different to normal because they have a distorted body image and irrationally think that they are fat when they are not.


Garfinkel & Gardner gave p's a series of photos of people and a device which allowed them to adjust the pictures to make the people look fatter or thinner. Although, anorexics only distorted the pictures of themselves to make themselves look much larger than they are.


+ This theory shows how people with eating disorders think about their bodies and has lead to therapies designed to help people w/eating disorders.

- Cause and Effect not clear. Distorted image -> disorder or disorder -> distorted image.




Made by Sarah Lewis