-As they are over reliant on their parents, they feel used and exploited and struggle for autonomy.
-Eating behaviour is the one area that they can control, and this becomes excessive leading to a disorder.
Crisp
-Says that self-starvation and loss of body weight lead to menstruation postponement in pre-pubertal girls.
-Leads to loss of menstruation in post pubertal girls. This was an attempt to postpone the onset of adulthood.
Family systems theory - Minuchin
-Suggests that the development of AN serves the function of preventing family arguments.
-It may be the adolescents’ attempt of preventing a divorce by diverting attention onto them.
-The joint concern for the child will bring the parents back together.
Commentary
Support for Bruch
- Steiner says that parents of teens with AN tend to define their child’s physical needs rather than the child.
- Research also claims that those with AN rely on others opinions and views, and have a lack of control.
Relationship between child and parents
-In most cases of eating disorders, there are complex interactions between children and parents.
-Evidence mainly comes from case studies, hard to replicate.
-However, forms of psychotherapy and family therapy have been used in treatment of eating disorders.
Ethical Issues
-Socially sensitive research, as questions can provide answers that participants did not intend to reveal.
-Quantitative data is taken from chat rooms and forums, this show a lack of informed consent & privacy.
Discuss two or more biological explanations of one eating disorder
Neural explanations
The role of neurotransmitters
-Early studies found evidence of disturbance of serotonin systems in the brain of those with AN.
-However, these people already had AN whilst being studied, possible that the disorder produced this.
-PET scans can be used to estimate the number of serotonin receptors in the brain.
-Kaye found that there are few receptors in people with eating disorders and people who’ve recovered.
-Evidence from PET scans suggests a link between dopamine and AN.
-Kaye compared dopamine activity in the brains of 10 women recovering from AN with 12 healthy women.
-AN women have an over activity of dopamine in the basal ganglia, alters the way they interpret rewards.
-They find it difficult to associate good feeling with things that people find pleasurable, e.g. food.
Commentary
- Part of the hypothalamus that controls feeding behaviour. Serotonin has been implicated in AN trait.
- SRRIs are ineffective when used with AN patient; however Kaye found that they prevented a relapse.
- Wang et al found there were normal levels of dopamine receptors in obese individuals.
- Treatment implications force patient to reduce any guilt caused by the view that it’s the parents fault.
- Gender bias, not necessarily a female only problem.
Genetic explanation
Compare rates of AN in MZ twins with rates in DZ twins.
Holland et al and Kendler et al found that concordance rates for MZ twins were significantly higher.
Bulik concluded from these studies that the genetic contribution to both AN and BN is 50-80%
Holland et al
- To investigate the genetic contribution to AN using MZ and DZ twins, one has been diagnosed with AN.
- 30 female twin pairs (16 MZ and 14 DZ), four male twin pairs and one set of male triplets.
- 55% concordance rate for MZ, 7% for DZ.
- Five of the non-anorexic female co twins had either other psychiatric illnesses or minor eating disorders.
- Research suggests that there is a genetic basis among females, due to the 55% concordance rate.
Commentary
- Methodological issues - studies are based on a small number of participants
- Environmental influences - MZ twins may have been brought up very similarly.
- Findings prove that it’s nature AND nurture, as the concordance rate would have been 100%
- Diathesis stress model suggest that people inherit vulnerability (diathesis) which develops anorexia.
Discuss two or more ways in which eating and satiation are controlled by neural mechanisms
Homeostasis
-The maintenance of a constant internal environment.
-In terms of hunger, the body has a sense of what is acceptable and regulates eating around this
The hypothalamus
-Hetherington & Ranson demonstrated that lesions of the ventromedial hypothalamus caused rats to overeat
-Researchers assumed that the VMH was a ‘satiety centre’, activated when an animal is full.
-Anand & Brobeck found that a lesion in the lateral hypothalamus led to ‘aphagia’ - loss of feeding behaviour
-Proposed that the function of LH was to stimulate feeding, later studies confirmed this.
Signals for starting a meal
Ghrelin
-A hormone secreted from the stomach and the amount released is proportional to stomach emptiness
-Cummings found that injections of ghrelin increase food intake and body weight in animals & humans.
-Gastric bands reduce ghrelin secretion in the stomach.
Signals stopping the intake of food: meal size
Cholecystokinin (CCK)
-Smith, Gibbs and Kulkosky found that inject of CCK in animals and humans reduce meal size.
-Also, animals with a genetic mutation eliminating the CCK system become obese.
-This suggests that CCK signals satiety to the brain and contributes to the control of meal size.
Signals controlling food intake: body weight
Leptin
-This is a hormone released from fatty tissue
-Research says it’s an indicator of body weight to hypothalamic mechanisms controlling long term food intake
-It’s released from fat cells into bloodstream which travels to the hypothalamus and acts as a satiety signal.
-Injections into the ‘ob’ mice stop them eating as much and their weight returns to normal (Carlson)
Commentary
-Recent research suggests that eating behaviour is controlled by neural circuits that run throughout the brain.
-Sakurai suggests that the LH is not the brains ‘eating centre
-Gold suggested that lesions restricted to the VMH alone did not result in overeating.
-Can help to develop medical interventions and explains some individual differences.
-Reductionist, as feeding is a complex behaviour e.g. mood, culture and experience can effect feeding.
-Luter suggests the body produces additional quantities of ghrelin in response to stress. Natural defense.
-Cummings research only had four male participants, hard to generalize to the population & women.
-Generalizing from humans to animals is difficult.
Discuss two or more evolutionary explanations of food preferences
Preference for high-fat foods
-Calories are essential to provide energy for the body to function; humans will have learnt this at an early age
Preference for sweet foods
-This preference would encourage consumption of ripe fruit, advantageous as it provides important calories.
-Therefore, it would have been adaptive for humans to have evolved with an innate preference for sweetness
Preference for meat
-Without meat, its claimed humans wouldn’t have gained enough nutrition to become active and intelligent
-A diet containing meat is a far more efficient means of obtaining protein.
-Large occasional kills would mean that humans spend less time feeding themselves and the group
Taste aversion
-If we eat food that makes us sick, it would be an evolutionary advantage to avoid that food in the future.
-Garcia, Rusiniak and Brett made wolves sick with contaminated lamb’s meat, they would later leave sheep.
-Suggests that they had learned to associate the poison with the sheep.
-Contributes to keeping the animal alive as it will affect the animal’s behaviour in the future.
Commentary
-Evolutionary explanations can account for innate food preferences, increased level of world obesity.
-Capaldi found that all ages and other species prefer sweet food tastes than any other taste.
-Bell found that it’s not culturally learnt, as Eskimos preferred sweet foods.
-Gibson and Wardle found that children were likely to choose bananas and potatoes, rich in calories.
-This suggests an evolved preference for calorie rich foods.
-Cultural differences can be seen as ‘fine tuning’ of evolved preferences.
-Reductionist as it ignores the influence of other factors such as cognitions, emotions and social factors.
-Determinist as they propose that eating behaviour is determined by previous environments, no free will.
