EDs: Anorexia Nervosa- Biological Explanations

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What does the genetic explanation of AN suggest?
That people inherit the tendency to develop anorexia.
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How would they find evidence for the genetic explanation?
Compare no. of cases in genetic relatives of anorexics w/ the no. of cases in general population and look at twin studies & compare concordance rates.
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What percentage of the population is affected by anorexia?
0.5-1%- therefore any individual has a 0.5-1% chance of developing the disorder.
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What is the percentage when a family member has AN and how does this support the genetic argument?
Where at least 1 relative has the disorder there is a 4-5% chance of other relatives getting the disorder which shows when we share genes w/ AN sufferers, we are more likely to get it than the general population.
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What could be another reason for MZ twins developing the same disorder apart from genetics?
Generally twins share same environment therefore the development of anorexia may have more to do with environment than genes.
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What study can be used to support the genetic explanation?
Holland et al.
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What did Holland do?
Followed up women who had anorexia and a twin (30 female twins- 16MZ, 14DZ- 4 male twins & 1 triplets). Looked at med records and interviewed each twin. 2nd twin had anorexia= concordant, 2nd twin didn't= discordant.
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What were Holland's results?
55% of the monozygotic twins were concordant, 7% of the dizygotic twins were concordant, in 5 cases where the other fem twin didn't have anorexia they had either a minor eating disorder or pscyh illness.
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How does this support the genetic explanation?
Suggests that genetic factors must play a role because concordance rates are significantly higher for MZ than DZ twins, and much higher than the national average (0.5-1%).
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Evaluate Holland et al.
- = culture&gender bias (American, female- BUT + = 90-95% of anorexics are fem), small sample size, corr. not causal, should be 100% if purely genetic. + = more than 1 measure of anorexia, high external validity (ecological val).
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What neurotransmitter is linked to Anorexia Nervosa? How?
Serotonin- studies from 5 years ago suggest that serotonin levels were low in anorexics. PET scans of the brain have shown that there are less serotonin receptors in brains of people with ed's. These changes are there after recovery. (Kaye et al)
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What has serotonin also be linked to?
Depression, OCD and the personality traits: perfectionism and anxiety. (typical behaviour of anorexics). Also linked to feeding centre of brain: lateral hypothalamus.
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Evaluate the neurological explanation.
- = corr not causal- cause or effect? (serotonin comes from food- no food=low serotonin. low receptors=long term complication of illness). + = Maudsley Hosp found anorexics 2x likely to have gene variation that controls brain's serotonin system.
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What is Walter Kaye's alternate theory with serotonin?
Suggests that overly high serotonin levels cause anxiety so anorexics reduce food intake to lower it & it makes them less anxious. So they stop eating and take it too far.
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What's an alternative neurological explanation?
Anorexics have a dysfunctional lateral hypothalamus (lesioning this part in rats lead to aphagia), or, lateral hypothalamus isn't responding to stretch receptor signals from the stomach and/or ghrelin.
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What does the evolutionary explanation suggest?
Anorexic behaviour must have some benefit for survival of a species, otherwise it wouldn't be passed down generations.
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What's the name of Guisinger's hypothesis?
Adapted to flee famine hypothesis (AFFH)
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What is the AFFH?
Suggests that when hunter-gatherers had to be where food supplies were, AN would have helped them to survive: the denial of hunger & restlessness of anorexics despite their hunger (non-AN get lethargic) would help them flee famine.
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What does Africa have to do with the AFFH?
Africa was the 'cradle of humanity' and the AFFH suggests that all the anorexics were able to leave Africa and move to other countries as a result of famine- which explains why anorexia is basically non-existant in Africa.
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What are the weaknesses of AFFH?
No direct evidence, only circumstantial (BUT + = in the context of law circumstantial evidence is enough), according to the theory anorexia should be gender balanced, 1 in 5 anorexics die: any hunter-gatherer who refused food would die early on.
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What is a strength of AFFH?
Having the occasional person who behaved like this would be beneficial for the group- INCLUSIVE FITNESS (benefits group not individual). Person's relatives would benefit and therefore genes would be passed on.
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What are the issues of the Biological Explanation?
Culture Biased (usually American), Gender Biased (female research), Ethics (sensitivity needed in talking of mental disorders).
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What are the debates of the Biological Explanation?
Nature v Nurture (dominant on nature side- ignores environmental factors), Reductionist (ignores SLT, etc.), Free Will v Determinism (anorexia can't be prevented), Is Psychology a Science? (evolutionary theory is unfalsifiable).
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How would they find evidence for the genetic explanation?

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Compare no. of cases in genetic relatives of anorexics w/ the no. of cases in general population and look at twin studies & compare concordance rates.

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What percentage of the population is affected by anorexia?

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Card 4

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What is the percentage when a family member has AN and how does this support the genetic argument?

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What could be another reason for MZ twins developing the same disorder apart from genetics?

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