Brain & neurotransmitters causing AN

Question 1

What is the background behind biological explanations of AN? (2 points)

Answer 1

They propose that the thoughts, emotions and behaviours patients exhibit have a biological basis - neurotransmitters and brain regions

The neurotransmitter explanation suggests chemical imbalances in the brain are the underlying cause of AN
E.g. changes in dopamine, endorphin and serotonin levels

Question 2

What are the 4 biological causes of Anorexia Nervosa?

Answer 2

Abnormal VMH & LH
Serotonin
Dopamine
Endorphins

Question 3

How does an abnormal VMH & LH cause AN? (4 points)

Answer 3

Lateral Hypothalamus (LH) - ‘hunger centre’
When stimulated, people feel hungry and they will eat

Ventromedial Hypothalamus (VMH) - ‘satiety/ full centre’
When stimulated, people will stop eating

Lesions cause abnormal neurone signalling:
LH - appetite is lost and eating is stopped, causing a form of anorexia
VMH - eating will continue, causing a form of obesity

Question 4

How does serotonin cause AN? (3 points)

Answer 4

AN patients are shown to have significantly lower levels of serotonin metabolites Tryptophan/5-HIAA in their cerebrospinal fluid compared to non-sufferers

Tryptophan - an amino acid consumed through the diet
1. Starvation causes less Tryptophan consumption
2. Less serotonin synthesised
3. Dysfunction of serotonin levels in anorexics

After long-term recovery from anorexia, patients have significantly increased serotonin levels, which may cause increased anxiety and obsessive behaviours

Question 5

How does dopamine cause AN? (2 points)

Answer 5

AN patients are shown to have naturally high levels of dopamine (hyperdopamin-ergic)

They do not seek pleasurable activities like eating, which can lead to the onset of weight loss and AN symptoms

Question 6

How do endorphins cause AN? (4 points)

Answer 6

Endorphins released during exercise from the pituitary gland are ‘endogenous morphine’

They bind to opiate receptors on presynaptic neurones to reduce the perception of pain/stress

Some AN patients are shown to have high levels of endorphins - could be explained by them carrying out repeated and excessive exercise

This would cause them to become addicted to the positive effect of endorphins on the body

Question 7

What are the supporting and refuting arguments for the neurotransmitter explanation of AN?

Answer 7

Supporting:
S - Research studies
C - PET scans and T&S
A - DBS

Refuting:
O - Genetics and SLT
D - Reductionist

Question 8

How do research studies support the neurotransmitter explanation of AN? (3 points)

Answer 8

The neurotransmitter explanation of AN is supported by several research studies including:
+ Bailer et al. (2012)
+ Kaye (2009)
+ Gorwood et al (2002)

They show that serotonin level disturbances may be responsible for producing AN’s characteristic symptoms such as appetite suppression and obsessiveness

This tells us that there is an extensive research base which is in favour of the neurotransmitter explanation for AN

Question 9

How does Bailer et al. (2012) support the neurotransmitter explanation of AN?

Answer 9

Found neurotransmitter imbalance in AN patients with higher dopamine and lower serotonin levels

Question 10

How does Kaye (2009) support serotonin being a cause of AN? (3 points)

Answer 10

Proposed that anorexia sufferers experience a vicious cycle where starvation makes them feel better by decreasing serotonin levels in their brains

When they begin to eat again, their serotonin level spikes, causing extreme anxiety and emotional chaos

They need to starve to feel better again

Question 11

How does Gorwoodet al (2002) support the neurotransmitter explanation of Sz? (2 points)

Answer 11

Found that anorexia patients are more likely to carry a particular variant of the 5-HT2A serotonin receptor

Thought to increase the amount of serotonin in the brain during the non-starved recovery state

Question 12

How credible is the neurotransmitter explanation of AN? (5 points)

Answer 12

Can also be considered a credible explanation - quantified and falsified using current scientific techniques

For example, PET scans:
+ Can visualise brain functioning which enables human eating behaviours to be studied directly
+ Can be repeated easily to test for reliability

Furthermore, psychologists have tested brain regions linked to the neurotransmitter explanation using standardised laboratory procedures

Thornhill & Saunders’s (1984):
Injecting Naloxone (a receptor antagonist) into the VMH and LH of food-deprived rats caused a decrease in food intake compared to a control group given saline injections

The neurotransmission explanation can be falsified by empirical research studies

Question 13

How is genetics an alternate explanation for AN? (5 points)

Answer 13

The neurotransmitter explanation is limited by the fact that AN often runs in families, implying the role of genetics - supported by Strober et al (2000):

Twin studies demonstrate that individuals may inherit a gene variant, increasing the likelihood towards developing an eating disorder

Kipman et al (1999):
Concordance rates for AN:
MZ: 44%
DZ: 12.5%

Possible candidate gene that genetically pre-disposes people to AN as shown in Scott-Van Zeeland et al. (2013)

This tells us that neurotransmission alone is not a complete explanation for AN

Question 14

How does Strober et al (2000) support genetics as an alternate explanation for AN?

Answer 14

Family studies have shown that first-degree relatives of individuals with AN have a 10 times greater chance of developing AN than relatives of unaffected individuals

Question 15

How does Scott-Van Zeeland et al. (2013) support genetics as an alternate explanation for AN? (2 points)

Answer 15

Found an association between the EPHX2 gene variant which codes for the enzyme Epoxide Hydrolase involved in cholesterol regulation

Anorexics tend to have an aversion to foods rich in fat - might be explained by EPHX2 which could be used as an anorexia biomarker

Question 16

How might twin studies limit the genetic explanation of AN? (2 points)

Answer 16

Conclusions drawn from twin studies and are difficult to test for reliability - MZ twins are likely to share both the same genetics and environment

The fact that concordance rates for twin studies like Kipman’s are not 100% for MZ, despite sharing 100% DNA, suggests the role of other non-biological factors

Question 17

How is SLT an alternate explanation for AN? (3 points)

Answer 17

Unclear whether the onset of AN is caused by biology or by the environment in which they were brought up in

Bandura’s Social Learning Theory suggests that eating disorder behaviour can be learned through meditational processes:
1. Paying attention to the behaviours exhibited by desirable role models
2. Retention of exercise routines and diet plans
3. Motor reproduction to imitate observed behaviours
4. Motivation provided through positive reinforcement like receiving ‘likes’ on social media

Supported by Becker et al (1998) - shows that biological explanations of AN are not complete

Question 18

How does Becker et al (1998) support SLT as an explanation of AN? (3 points)

Answer 18

Showed the impact of Western TV and media exposure caused disordered eating attitudes and behaviours among media-naïve indigenous Fijian adolescent girls

EAT-26 scores increased from 12.7% in 1995 to 29.2% in 1998

Participants also felt that television content had influenced their body image in a negative way

Question 19

How is the neurotransmitter explanation of AN reductionist? (4 points)

Answer 19

The neurotransmitter explanation is biologically reductionist - focuses on parts of human biology but does not address the interaction between the different parts

The effort to isolate serotonin as the single neurotransmitter responsible for AN is oversimplistic - in reality, serotonin interacts with dopamine, where both are precursors to noradrenaline, which may also interact with the neurotransmitter GABA

Furthermore, drugs like SSRIs used to treat AN by regulating serotonin levels, do not explain the underlying cause of the eating disorder and merely address the symptoms

Therefore, the neurotransmitter explanation fails to account for social, cognitive and environmental factors

Question 20

How is the neurotransmitter explanation of AN applicable to real life? (4 points)

Answer 20

The application of the neurotransmitter explanation could be very important in future medical therapies

Deep-brain stimulation (DBS) to the Nucleus Accumbens of the limbic system could be a potential treatment for AN

The efficacy of such future treatments for AN is supported by Whiting (2018)

The neurotransmitter explanation could lead to new medical therapies that could significantly benefit society as a whole

Question 21

How does Whiting (2018) support the neurotransmitter explanation of AN being applicable to real life? (2 points)

Answer 21

Conducted a review of studies for DBS treatment in the VMH and LH of 16 human anorexic patients

Results showed significant improvement in BMI and other psychological symptoms