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Biological Explanations for Anorexia Nervosa

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Psychology Group

on 7 November 2013

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Transcript of Biological Explanations for Anorexia Nervosa

Biological Explanations for Anorexia Nervosa
Neural Explanations
Neurotransmitters
SEROTONIN
Disruption of serotonin levels lead to
increased anxiety
, which may then
trigger AN
.
Bailer
et al found
high
levels of
serotonin
in women with binge eating AN, with highest levels in those with the
most anxiety
when comparing the characteristics of individuals with eating disorders.

DOPAMINE
Increased
dopamine activity in the
basal ganglia
alters the way people interpret
rewards
, so individuals with AN find it difficult to
associate
good feelings with things that are usually pleasurable (e.g. food).

AO2 Neurodevelopment
IDA Points
Gender Bias - most studies of eating disorders have been concentrated on the study of women, but according to statics, 25% of adults with eating disorders are men. Shows eating disorders such as AN are not exclusively a female problem.
Evolutionary Explanation
Neurodevelopment
AO2 Neurotransmitters
AO2 AFFH
AO2 problems associated with evolutionary
'Adapted to flee' famine hypothesis
Guisinger
- Typical AN symptoms of food restriction, hyperactivity (a form of migratory restlessness) and denial of starvation reflect
evolved adaptation
in response to
local famine.
When individuals lose weight, adaptive mechanisms usually cause
conservation of energy
and increased
food desire.
Anorexics '
turn off
' this so that they increase their chances of
survival
by moving to a more favorable environment with more
resources
.
- Surbey (1987): Adolescent girls' desire for weight control is an
evolutionary adaptation
where ancestral girls avoided giving birth at times where conditions would be
difficult
for offspring to
survive
.

- In many species, reproduction is
suppressed
in females when they're in poor physical condition.

- Anorexia is a
'disordered variant'
of this ability.
Reproductive Suppression Hypothesis
Obstetric Complications
-
Favaro et al
. (2006) carried out a prospective birth study. Found
perinatal complication
significantly associated with the risk of developing AN.
Placental infarction
associated with
early eating difficulties
and
low birth weight
. Study
supports
the contribution of obstetric complications.
Season of Birth
- Eagles et al. (2005) Found anorexic individuals tend to be later in birth order compared to healthy individuals. More elder siblings a child has while its still in the womb, more likely the mother will be exposed to common infections, so there will be more chance they will be passed to the unborn child. Critical period for brain development is the second trimester of pregnancy, so for spring births second trimester would occur at the time of year when infections are more likely. Supports explanation.
Pregnancy and birth complications
-
Lindberg and Hjem
(2003) found a significant association between
premature birth
and the development of anorexia nervosa (AN). Birth complications could lead to
brain damage
caused by lack of oxygen
(hypoxia)
, this impairs the
neurodevelopment
of the child.
Nutritional factors may be implicated if
mothers
have an
eating disorder
.
Builk et al
. (2005) suggested that mothers with AN expose their offspring to a
'double disadvantage'
- this being the transmission of a
genetic vulnerability
to AN, also
inadequate nutrition
during pregnancy.

Season of birth
- In addition research by
Eagles et al
. suggests that individuals with AN are more likely to have been born during
spring
months. The explanations for this include
intrauterine
infections (infections that occur in the womb) and the
temperature
at the time of the conception. In one study
Willoughby
et al. found among patients with AN in
equatorial
regions, where it is constantly a hot temperature, there was
no seasonal effect
in the development of AN.
Serotonin
Kaye et al
found that when using
SSRIs
in recovering anorexia patients, they help prevent relapses. This is because malnutrition changes in serotonin that
inhibit
SSRIs only become effective when weight comes to a more
normal
level.
Dopamine
There is research to suggest that the
level of dopamine
in the body is a
direct result
of
body weight
.
Castro-Fornieless et al
found that teenage anorexia sufferers had
high levels
of
homovanillic
acid which is a waste product of dopamine, and that
normalisation
of weight resulted in
lower
homovanillic levels.
Wang et al
found
low
levels of dopamine
receptors
in
obese
individuals, showing that weight affects the levels of dopamine in the body.
Treatment Implications
An advantage of using the biological explanation of anorexia is the wide range of possible treatments. Because we know who is biologically more prone to developing anorexia, it could be possible to develop prevention techniques that could be offered to them. (Bulik)
Another implication of using biological treatments to explain anorexia is that it blames biology, rather than personal circumstances. Treating a biological illness is much easier than treating a whole family, if we were to go with the psychological explanation of anorexia. It places less ‘blame’ on the family, as they know they are not the ones who ‘caused’ anorexia, but that it actually occurred biologically.

AO2 reproductive suppression hypothesis
Observation that supports this is that the onset of puberty (menarche) is
delayed
in
prepubertal
girls with anorexia nervosa, this therefore means that reproduction is effectively
suspended
in anorexic females

Guisinger
- claims that the AFHH "relieves therapists of the need to search for familial reasons for AN" There is a struggle for control between those with AN and those wanting to get better, this is often a reported characteristic of AN. This struggle can be explained in the terms of the 'worried and comprehending family' on one hand and the anorexic's powerful biological urge to avoid food and to exercise on the other.
When made aware of the causal influence, this can help treatment and aid parents to become more compassionate towards an anorexic child.
Biological determinism- a consequence of research into this area is its implication for insurance payouts for psychiatric conditions E.G in the US treatment for AN is restricted due to it not being 'biologically based'. However other research creates a case for insurance companies to consider AN in the same way as psychiatric conditions such as schizophrenia, which is considered to be biologically based.
Leads us to question how symptoms of AN might be passed on by
natural selection
, particularly as they
decrease
fertility and could lead to
death
of the individual with the condition. AN would have functioned more effectively in
ancestral
conditions, yet outside the ecological setting in which it evolved, disorders such as AN can be deadly.
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