18339387
Description
Mind Map by Katie Greensted, updated more than 1 year ago
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Created by Katie Greensted
almost 5 years ago
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Evaluation: Genetic Explanation of
Anorexia Nervosa
- Twin studies can be used to assess the
impacts of genes on the development of
anorexia. Mz twins share 100% of their genes;
Dz twins share 50%. They both share 100% of
their environment. If Mz twins show a higher
concordance rate than Dz twins, then this
suggests that some part of the disorder is
genetic.
- Holland et al found a 56% concordance rate in Mz
twins and a 5% concordance rate in Dz twins. This
suggests the more genetically similar you are to an
individual with anorexia, the more likely you are to
develop it.
- However, as Mz twins share 100% of their genes, a 100%
concordance rate would be expected if the cause of the
disorder was purely biological. This suggests that there
are potentially some environmental factors influencing
the development of anorexia. This could link to the
diathesis stress model which suggests that some genes
are triggered by environmental factors.
- However, as Mz twins share 100% of their genes, a 100%
concordance rate would be expected if the cause of the
disorder was purely biological. This suggests that there
are potentially some environmental factors influencing
the development of anorexia. This could link to the
diathesis stress model which suggests that some genes
are triggered by environmental factors.
- Holland et al found a 56% concordance rate in Mz
twins and a 5% concordance rate in Dz twins. This
suggests the more genetically similar you are to an
individual with anorexia, the more likely you are to
develop it.
- Family studies can be used to estimate the
percentage of any difference between family
members or twins that is due to genes. If
genes are an explanation of anorexia, then
the frequency of AN in the relatives of
someone with the disorder should be higher
than the general population.
- Strober et al found that in first degree relatives of
people with an eating disorder in the family,
anorexia was 11.3% more prevalent. This suggests
that anorexia is genetic to some extent as it is more
likely to occur in people who have it in the family.
- However, family studies do not separate nature from
nurture so we are unable to tell if these results are
influenced by environmental factors. For example,
Chadda found that family interaction patterns
influenced the weight loss of a 13 year old as her weight
loss was being reinforced by her parents.
- However, family studies do not separate nature from
nurture so we are unable to tell if these results are
influenced by environmental factors. For example,
Chadda found that family interaction patterns
influenced the weight loss of a 13 year old as her weight
loss was being reinforced by her parents.
- Strober et al found that in first degree relatives of
people with an eating disorder in the family,
anorexia was 11.3% more prevalent. This suggests
that anorexia is genetic to some extent as it is more
likely to occur in people who have it in the family.
- People with anorexia may inherit genes
that contribute to the development of the
disorder, but the question remains: how do
genes affect behaviour? One possibility is is
that they influence the activity of the
brain's neurotransmitter systems.
- The DAT1 gene is said to play a role in anorexia. The gene codes for
a protein which regulates the transport of dopamine between the
neon and the synapse. A dysfunction with this gene may lead to a
disruption of this process and a dysfunction of the brain's reward
system, therefore imparting motivation towards eating.
- This raises a question about whether
the cause of anorexia is a genetic
issue or a neurotransmitter issue.
- This raises a question about whether
the cause of anorexia is a genetic
issue or a neurotransmitter issue.
- The 5-HTR2A gene has been linked to anorexia and
codes for the 5-HT2A receptor. A mutation in this gene
may affect the structure of these receptors. This will
lead to less binding between serotonin and the
receptor, meaning that appetite-related information
will not be transmitted normally, perhaps leading to a
loss of appetite and therefore the individual may stop
eating.
- Walter and Kaye reviewed several studies
and found significantly decreased 5-HT2A
activity in the serotonergic system
throughout the brains of people with
anorexia, suggesting that a problem with
those receptors are linked to that disorder.
- Walter and Kaye reviewed several studies
and found significantly decreased 5-HT2A
activity in the serotonergic system
throughout the brains of people with
anorexia, suggesting that a problem with
those receptors are linked to that disorder.
- The DAT1 gene is said to play a role in anorexia. The gene codes for
a protein which regulates the transport of dopamine between the
neon and the synapse. A dysfunction with this gene may lead to a
disruption of this process and a dysfunction of the brain's reward
system, therefore imparting motivation towards eating.
- Genetic studies have
tried to identify genetic
variations linked to
anorexia.
- Two genes have be largely linked to anorexia. The
EPHX2 gene codes for the enzyme which regulates
cholesterol metabolism. It has been found that
many people with severe anorexia have
abnormally high levels of cholesterol.
- However, it is unclear whether the
dysfunction of this gene is a cause or a
consequence of the disorder, so is not
a solid explanation of anorexia.
- However, it is unclear whether the
dysfunction of this gene is a cause or a
consequence of the disorder, so is not
a solid explanation of anorexia.
- The ITPR gene has also been linked to anorexia. The gene
codes for a protein which codes for a receptor involved in
detecting different tastes. It has been suggested that a
genetically-determined dysfunction of the taste pathway
means that those with the disorder will be indifferent to
tastes, and therefore will not be motivated to eat.
- Anorexia is a polygenic disorder, so no single
gene can explain all the symptoms of anorexia.
Therefore any theory that suggests one gene is
the cause of this complex disorder risks
oversimplifying the explanation.
- Two genes have be largely linked to anorexia. The
EPHX2 gene codes for the enzyme which regulates
cholesterol metabolism. It has been found that
many people with severe anorexia have
abnormally high levels of cholesterol.
- Relatives not sharing the same home
environment still show a higher
tendency to develop AN when someone
has the disorder in their family than
relatives of control participants, This
suggests anorexia is at least some part
genetic.
- Woodside et al found that compared to the general population, first
degree relatives with the disorder are more likely to develop anorexia.
This is also true for third degree relatives, but to a lesser extent. This
suggests that genetics may cause anorexia to some extent as people
sharing genes with people with anorexia are more likely to develop the
disorder, even when they do not share the same environment.
- Woodside et al found that compared to the general population, first
degree relatives with the disorder are more likely to develop anorexia.
This is also true for third degree relatives, but to a lesser extent. This
suggests that genetics may cause anorexia to some extent as people
sharing genes with people with anorexia are more likely to develop the
disorder, even when they do not share the same environment.
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