Biological explanations for eating disorders

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  • Created on: 08-01-13 09:21

Biological explanations

first degree relatives of An- increased risk of developing eating disorder (strober & Katz) confounded by enviromental factors.
Supporting twin studies by:
Holland et al (1984) - 55% concordance rate for MZ twins compared to 7%DZ
Treasure & Holland (1991) suggests a genetic basi does not relfect a denetic cause,
Hs suggests genetics relate to personality traits (emotional instability) history of An linked to mental disorders.
Wade dissagrees- foudn significant enviromental influence in creatigns womans attitude to eating but little for related to genetics.
Holland et al study: A: Discover if MZ twins more likely to develop AN (100% genetics)
P: 30 pairs of twins used, at least one has AN, natural experiement.
F: MZ 55% concordance rate, DZ 7% concordance rate (quantitive statistical expresion)
C:high concordance MZ suggests genetific influence but other factors at work.
E: high MZ suggests small genetic factor, other factors at work, Natural experiemnt, high external validity, may be due to enviroment increasing risk of AN twins in same enviroment. twins used of very small population, not an accurate representation of the population.

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Biochemical explanations.

Hypothalamic disorder. (Hypo)
AN linked to abnormal hypo, LH + VMH work together for weight thermostat.
Keesey & Corbett, Lateral area = hunger, Ventromedial area = depresses hunger.
weight falls below thermostat lateral area is activated, rises, VM area activated.
Abnormal endocrine functioning.
amennorhoea may precede symptoms,low endocrine level associated with hypo dysfunction
endocrine levels in 19 year old anorexics similar to 9 year old girls.
problem with causality, beavioural symptoms effect a persons biochemistry
norepinephrine, dopamine + ow levels of serotonin.
Walsh- serotonin effective drug treatment for AN, AntiD decreases binge eating.
Explanations reductionist, AN reduced to neurochemicals ignoring cutlural influences.
Advantage  neurochemicals play key role in lead of treatment
difficult to say cause and effect, symptoms of An have direct and significant effect on persons physiology thus effect their biochemistry.starvation may cause imbalance in biochemical functioning.
Stress-Diathesis model,critise any study, underlying predisposition triggered my enviromental factors.

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The Behavioural Approach

Based on CC, slimming becomes a "habit" just like any other habit through stimuus r esponse mechanisms
OC:admiration from others reinforces dieting behaviour, refusal to eat = extra attention from pparents - neurotic paraddox, starvation = way to punishparents.
theory provides explanation of why people maintain AN, degree of success in behavioural therapires,Hallstein - rewarding clients for reaching and maintaining target boy weights.
Modeling/Social Learning Theory.
Alternative approach -
sociocultural pressures in western society on females.
cross cultural studies, more prevalent in western culture - Cooper 1994, support BH view.
Vicarious reinforcment from a young age to women, imitate perople we admire and identify. more than half Miss America 15% below expected BMI. more prevalent in Industrialised
Nasser- 50 egyptians in london, 60-Cairo, 12% london developed 0% ciaro
suppor Bh approach, if EDs were learnt would expect, industralised societies would have a higher proportion of Eds.
EDs rare in Hong Kong, Chinese value fatness and dieting is rare, eating not associated with guilt - Lee. suggesting soci-cultural factors lead to eating disorders rather than bio factors.

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Psychological approach

Peer acceptance important during adolensence, most susceptible to AN (Teasing)
Jones and crawford - overweight girls and underweight boys most likely to be teased, reinforce gener steryotypes.

Research not always show significant relationship of peer influence and development of AN
shoff and thompson- gender diffeerences done emerge until adolesecence.
males account for 5-15% of AN patients.increased to 10%-25%. sales of mens health increased. ED in males greater stigma than girls.
Garner et al. A: investigate cultural pressures to be thin
P:11-14 yr olds in ballet cshool assed for 2 years.
F:25% of girls develop anorexia. national average 0.5-1%
C: cultural pressure to be thin are influential.
E: study SUPPORTS claim that eating disorders caused by other factors.
observational study - high ecological validity, but has confounding variables.
ignores fact of other factors e.g genetic predisposition. stress- diathesis model,

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