Eating Behaviour
Anorexia Nervosa
Unit PSYA3
AQA A Specification
Factors influencing attitudes to food and eating behaviour. For example:
Eating behaviour cultural influences; psychological influences (mood); and social influences
(health concerns/media).
Explanations for the success and failure of dieting.
Biological
Neural mechanisms involved in controlling eating behaviour.
explanations of
eating behaviour Evolutionary explanations of food preference.
In relation to either anorexia nervosa or bulimia nervosa:
Eating disorders
Psychological explanations.
Biological explanations, including neural and evolutionary explanations.
What we have covered
Where we are now
What will we cover today?
Biological explanations





Genetic basis?
Serotonin
Dopamine
Lateral hypothalamus
Neurodevelopmental factors
Evolutionary explanations
 Reproductive success hypothesis
 Adapted to flee famine hypothesis
Does AN have a genetic basis?
Twin studies (Holland et al, 1984)
Looked at the concordance of AN between: 1)Identical twins – monozygotic (MZ), 100% of genes in common.
2)Non-identical twins – dizygotic (DZ), 50% of genes in common.
If the underlying cause of AN is genetic, then there should be a
higher concordance in MZ twins than in DZ twins (due to genes).
 56% of MZ twins both had AN compared to only 5% of DZ
twins.
 This suggests…
Evaluation
Twin studies (Holland et al, 1984)
Reductionist – only takes one factor (genes) into account.
The concordance rate for MZ twins was well below 100%.
This suggests…
For example, MZ twins may be treated more similarly than DZ
twins as they look more alike and therefore they may display
similar behaviours (environmental explanation).
Could be that genetics provide a predisposition to AN but
other factors also contribute and trigger the onset of AN.
Neural explanations
Changes in the nervous system
The role of serotonin in the development of AN
Read the two studies in your booklet and answer
the associated questions.
You have 10 minutes.
Evaluation of serotonin
- Selective serotonin re-uptake inhibitors (SSRIs –
drugs), which alter the levels of serotonin in the brain,
are ineffective when used with AN patients.
- I.e. using SSRIs to maintain/decrease the level of
serotonin does not aid the recovery of AN patients.
- This suggests…
Evaluation of serotonin
However, Kaye et al (2001) found that SSRIs were
effective in preventing relapse and maintaining
remission in recovering AN patients.
This suggests that malnutrition-related changes in
serotonin function may block the action of SSRIs, and
that these drugs only become effective when the
individual’s weight returns to a normal level (i.e. when
in recovery/remission to prevent a relapse).
Evaluation of serotonin
Evaluation of serotonin
Difficult to establish cause and effect.
Is this dysfunction in serotonin levels a cause of AN OR
is it a result of AN?
Dopamine and AN
Kaye et al (2005)
 10 women recovering from AN and 12 healthy women.
 Compared activity of dopamine receptors in the Basal Ganglia
using a PET scan of the brain.
 In this part of the brain, dopamine receptors plays a role in the
interpretation of rewards and pleasure, as well as weight and
feeding behaviours.
 FINDINGS: AN women – increased activity of dopamine
receptors in the Basal Ganglia.
Dopamine and AN
Kaye et al (2005)
 This suggests that alteration in dopamine function (i.e. increased
dopamine activity) in this brain area appears to alter the way AN
patients interpret rewards.
 For example, it suggests that AN patients may have difficulty
associating good feelings with things that most people find
rewarding and pleasurable, i.e. food.
Evaluation of dopamine and AN
+ Research has found that adolescents with AN had
higher levels of homovanillic acid (a waste product of
dopamine) than a control group. Improvement in weight
levels was associated with normalisation of homovanillic
levels. This supports… and suggests…
- Difficult to establish cause and effect.
- Is this increase in dopamine activity a cause of AN OR
is it a result of AN?
Brain areas
The development of AN can be linked to the hypothalamus.
Which part of the hypothalamus is linked to hunger?
Lateral hypothalamus.
If this area is damaged, what happens?
Loss of appetite, no feelings of hunger.
How can we relate this to AN?
If the LH is damaged in AN patients this could partially explain why they
starve themselves as they do not experience feelings of hunger.
However, it is much more likely that the development of AN is due to
many factors, not just damage to the LH which results in
undereating. For example…
Independent task
Complete the gap fill exercise on
neurodevelopment explanations of AN.
You have 10 minutes.
Treatment implications (IDA)
Biological explanations of AN offer the promise of a range of
treatment possibilities including:  Drug therapies to normalise NT levels (serotonin and
dopamine).
If we could use an individual’s genetic profile to indicate the
level of risk of AN, we could develop a specifically tailored
intervention programme for those susceptible to developing AN.
+ Dealing with dysfunctional biology which is treatable using
drugs.
Real-world application
Implication of insurance pay-outs for psychiatric conditions.
E.g. In the USA, treatment for AN is restricted under many
insurance plans as it is not considered to be ‘biologically-based.’
This research (serotonin/dopamine/lateral hypothalamus) creates
a case for insurance companies to consider AN in the same way as
other psychiatric conditions (e.g. schizophrenia) that are
considered to be biologically based.
IDA
Gender bias
 Most studies on eating disorders have studied females.
 However recent statistics indicate that 25% of the cases reported
are male.
 Has AN increased in males?
 Or did they just escape attention/diagnosis before?
 Clearly it is not exclusively a female problem.
 Can the findings be generalised if most studies are on females?
 Could be different causes of AN for the different genders.
Now, write your own!!!
A summary so far…
The development and maintenance of AN…
Dysfunction of Serotonin levels
Increased Dopamine activity in the Basal Ganglia
Role of the Lateral Hypothalamus
Neurodevelopment – pregnancy, birth complications
and season of birth
Over Easter…
• Read the page in your booklets on evolutionary
explanations of AN: 1)The reproductive suppression hypothesis
2)The ‘adapted to flee famine’ hypothesis
(AFFH)
• Essay structure for EDs Q.