Brain & neurotransmitters causing AN Flashcards
What is the background behind biological explanations of AN? (2 points)
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
What are the 4 biological causes of Anorexia Nervosa?
Abnormal VMH & LH
Serotonin
Dopamine
Endorphins
How does an abnormal VMH & LH cause AN? (4 points)
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
How does serotonin cause AN? (3 points)
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
How does dopamine cause AN? (2 points)
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
How do endorphins cause AN? (4 points)
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
What are the supporting and refuting arguments for the neurotransmitter explanation of AN?
Supporting:
S - Research studies
C - PET scans and T&S
A - DBS
Refuting:
O - Genetics and SLT
D - Reductionist
How do research studies support the neurotransmitter explanation of AN? (3 points)
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
How does Bailer et al. (2012) support the neurotransmitter explanation of AN?
Found neurotransmitter imbalance in AN patients with higher dopamine and lower serotonin levels
How does Kaye (2009) support serotonin being a cause of AN? (3 points)
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
How does Gorwoodet al (2002) support the neurotransmitter explanation of Sz? (2 points)
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
How credible is the neurotransmitter explanation of AN? (5 points)
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
How is genetics an alternate explanation for AN? (5 points)
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
How does Strober et al (2000) support genetics as an alternate explanation for AN?
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
How does Scott-Van Zeeland et al. (2013) support genetics as an alternate explanation for AN? (2 points)
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
How might twin studies limit the genetic explanation of AN? (2 points)
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
How is SLT an alternate explanation for AN? (3 points)
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
How does Becker et al (1998) support SLT as an explanation of AN? (3 points)
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
How is the neurotransmitter explanation of AN reductionist? (4 points)
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
How is the neurotransmitter explanation of AN applicable to real life? (4 points)
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
How does Whiting (2018) support the neurotransmitter explanation of AN being applicable to real life? (2 points)
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
