Biological Explanations to AN Flashcards
What are the 2 types of biological explanations for AN?
1) Neural
2) Evolutionary
What do we mean by neural explanations?
Changes in the neural system
What do we mean by evolutionary explanations?
Adaptive functions of AN
How many neural explanations are there for AN?
3
Name the 3 neural explanations of AN
1) Serotonin
2) Dopamine
3) Neurodevelopment - pregnancy and birth complications
What is the main study for serotonin in AN?
Bailer (07)
Outline Bailer (07)
Compared serotonin activity in women recovering from restricting-type AN (restricted food intake), and binge-eating/purging type (periods of restricted eating and binge-eating/purging) with healthy controls - found significantly higher serotonin activity in women recovering from binge-eating/purging type - in addition, found highest levels of serotonin activity in women who showed most anxiety, suggesting that persistent disruption of serotonin levels may lead to increased anxiety which may trigger AN
What is the main study for dopamine in AN?
Kaye (05)
Outline Kaye (05)
Used PET scans to compare dopamine activity in brains of 10 women recovering from AN and 12 healthy controls - in AN women, found over activity in dopamine receptors in part of brain known as basal ganglia where dopamine plays part in the interpretation of harm and pleasure - increased dopamine activity in this area appears to alter way people interpret rewards - individuals with AN find it difficult to associate good feelings with things most people find pleasurable like food
What are the 2 main studies for pregnancy and birth complications for AN?
1) Lindberg & Hiern (03)
2) Bulik (05)
Outline Bulik (05)
Suggest mothers with AN expose their offspring to a ‘double disadvantage’ - transmission of genetic vulnerability to AN and inadequate nutrition during pregnancy
Outline Lindberg & Hiern (03)
Found significant association between premature birth and development of AN
Outline pregnancy and birth complications for the biological explanations of AN
Birth complications may lead to brain damage caused by hypoxia (lack of oxygen), impairing neurodevelopment of the child - nutritional factors may be implicated if mothers have an eating disorder
What are the 2 evolutionary explanations of AN?
1) Reproductive Suppression Hypothesis
2) The ‘adapted to flee’ hypothesis
Outline Reproductive Suppression Hypothesis for AN
Surbey (87) suggest adolescent girls’ desire to control their weight represents an evolutionary adaptation in which ancestral girls delayed the onset of sexual maturation in response to cues about the probability of poor reproductive success - ability to delay reproduction is adaptive because enables female avoid giving birth at time when conditions are not conductive to her offspring’s survival - argues AN is disordered variant of adaptive ability of females to alter timing or reproduction at a time when they feel unable to cope with biological, emotional and social responsibilities of womanhood
What is the Reproductive Suppression Hypothesis for AN based on?
The observation that in a number of species, puberty delayed or reproduction suppressed in females when subjected to stress or are in poor physical condition
Who came up with the ‘adapted to flee’ hypothesis ?
Guisinger (03)
Outline the ‘adapted to flee’ hypothesis for AN
Proposes typical AN symptoms of food restriction, hyperactivity and denial of starvation reflect operation of adaptive mechanism that once caused migration in response to local famine conditions - normally, when person begins to lose weight, physiological mechanism conserve energy and increase desire for food - these adaptations facilitate survival in hard times - however, among ancestral nomedic foragers, when extreme weight loss due to severe depletion of local food resources, this adaptation must be turned off so that individuals can increase chances of survival by migrating to more favourable environment - food restriction is common feature of many species when feeding competes with other activities such as migration or breeding
Evaluate serotonin for AN
SSRIs (alter levels of available brain serotonin) ineffective when used with AN patients - Kaye (01) however found when used with recovering AN patients, effective in preventing relapse - malnutrition-related changes in serotonin may negate action of SSRIs which only become effective when weight returns to more normal level
What are 2 evaluative studies on dopamine for AN?
1) Castro-Fornieles (06)
2) Wang (01)
Outline Castro-Fornieles (06)
Found adolescent girls with AN had higher levels of homovanillic acid (waste product of dopamine) than a control group - improvement in weight levels associated with normalisation of homovanillic levels
Outline Wang (01)
Found lower than normal levels of dopamine receptors in brains of obese individuals
Evaluate dopamine for AN
Levels of dopamine appear to be related to body weight, but not clear as to whether this is a cause or consequence
What is the key study for the evaluation of neurodevelopment for AN?
Favaro (06)
Outline Favaro (06)
Followed group of children from birth to adulthood - found perinatal (immediately before or after birth) complications significantly associated with risk of developing AN were placental infarction (obstructed blood supply in the placenta), early eating difficulties and low birth weight
Evaluate the reproduction suppression hypothesis for AN
Supported by observation that menarche (onset of puberty) is delayed in prepubertal girls with AN - also amenorrhoea typical characteristic meaning reproduction is effectively suspended in anorexic females
Evaluate the ‘adapted to flee’ hypothesis
There are treatment implications - Guisinger claims struggle for control between those with AN and those who want them to get better is typical characteristic of AN - awareness of this can help treatment and encourage parents to be more compassionate toward anorexic child
Evaluate the problems associated with using evolutionary explanations for AN
Might question how symptoms of AN might be passed on by natural selection particularly as they decrease fertility and could even kill the individual
Name 4 general positive evaluative points about biological explanations
1) Evidence to support the biological basis
2) Can lead to successful drug therapies as drugs which reduce serotonin can be effective
3) Linked to biological explanations so people realise they are dealing with dysfunctional biology (treatable) and not dysfunctional family - reduces guilt generated by view parents cause development of eating disordered in children
4) Explains why people with AN display abnormal eating patterns
Name the 7 general negative points about biological explanations
1) Often small samples
2) No one biological mechanism has been found as the cause of the disorder
3) Cannot account for recent increase in AN
4) Cannot explain why there isn’t 100% concordance for AN in twins
5) Cannot explain massive sex differences in incidence
6) Do not explain psychological aspects: intense fear of fat, distorted body image, and also need psychological, social and cultural factors
7) Gender-bias - most studies concentrate on women but 25% of adults with eating disorders are men
Outline the diathesis-stress model for AN
Possible some individuals born with biological predisposition to develop AN - inherit vulnerability or risk factor - the diathesis - key vulnerability of AN is obessionailty - this is then triggered by life stressors, like in the teenage years - biological mechanism may perpetuate the illness
