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Biological Explanations for Anorexia Nervosa

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Livvy Foster

on 4 November 2013

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Transcript of Biological Explanations for Anorexia Nervosa

Biological Explanations for Anorexia Nervosa
Neural Explanations
Serotonin -
disturbances in levels of the neurotransmitter serotonin - characteristic of individuals with eating disorders
Bailer et al. (2007)
compared serotonin activity in women recovering from restricting-type anorexia / binge-eating/purging type with healthy controls
found - higher serotonin activity in women recovering from BE/PT
also found - highest levels of serotonin activity in women who showed most anxiety
suggests - persistent disruption of serotonin levels - leads to increased anxiety - triggers AN
Dopamine -
Kaye et al. (2005)
used PET scan to compare dopamine activity in brains of 10 women recovering from AN / 12 healthy women
in AN women - found overactivity in dopamine receptors in a part of the brain known as the basal ganglia
basal ganglia - where dopamine plays a part in the interpretation of harm and pleasure
increased dopamine activity in this area - alter the way people interpret rewards
individuals with AN - find difficult to associate good feelings with the things that most people find pleasureable
Evolutionary Explanations
The Reproductive Suppression Hypothesis
Surbey (1987) -
suggests adolescent girls' desire to control weight represents evolutionary adpatation 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 - enables a female to avoid giving birth when conditions are not conducive to her offspring's survival
this model - based on observation that in a number of species puberty is delayed / reproduction suppressed in females when subjected to stress / in poor physical condition
Surbey argues - AN is a 'disordered variant' of adaptive ability of females to alter timing of reproduction at a time when they feel unable to cope with biological, emotional and social responsibilities of womanhood
Serotonin -
problem - SSRIs, which alter levels of available brain serotonin, are ineffective when used with AN patients
Kaye et al. (2001) -
found - when used with recovering AN patients - these drugs were effective in preventing relapse
malnutrition-related changes in serotonin function - negate the action of SSRIs - only become effective when weight returns to a more normal level
Dopamine -
Castro-Fornieles et al. (2006) -
found - adolescent girls with AN - higher levels of homovanillic acid - waste product of dopamine) than a control group
improvement in weight loss - associated with normalisation of homovanillic levels
research also shown lower than normal levels of dopamine receptors in brains of obese individuals (Wang et al. 2001)
levels of dopamine - appear to be inversely related to body weight - although, whether a cause or a consequence not clear yet
The Reproduction Suppression Hypothesis
this hypothesis - supported by observation that menarche (onset of puberty) is delayed in prepubertal girls with AN
since amenorrhoea is a typical characteristic of AN - means reproduction is effectively suspended in anorexic females
Gender Bias -
most studies of eating disorders concentrated on study of women
according to recent statistics - 25% of adults with eating disorders are men
eating disorders such as AN - not exclusively a female problem
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