Anorexia: Neural mechanisms

Serotonin

• High levels of serotonin have been linked to appetite suppression
• Serotonin is thought to activate melanocortin-4 receptors, which curbs hunger
• It blocks neurons that increase appetite 
• It could be suggested that anorexics have especially high levels of serotonin

AO2

• Serotonin injections: shown to exert a continued appetite supression
• Stimulates obssesive behaviour: this is behaviour typically shown in AN sufferers
• Diet drug Fen-Phen: Increases serotonin activity in the brain to suppress appetite
• However, suffers from 'Treatment Actiology Fallacy', just because it facillitates weight loss does not mean that it is involved in anorexia 

Dopamine

• Responsible for transmitting reward signals withing the brain
• Suggested there are several different version of the gene which controls how many dopamine receptors we have
• People with genetically more dopamine are less motivated to eat less food because they only need a bit to gain pleasure 
• Suggested that AN sufferers have this

AO2

• Kaye et al: PET scans tracked dopamine levels, found that after a dose of amphetamines AN sufferers reported anxiety, whereas control group felt pleasure
• Castro-Fornieles et al (2006): Adolescent girls with AN had a higher level of homovanillic acid (dopamine waste product) and improvement of weight was associated with a normalisation of homovanillic acid
• Cannot be sure: May actually be starvation thta causes high levels of dopamine or there could be a third variable involved 

Hypothalamus

• LH could be damaged which causes the VMH to become over-activated in response
• Hunger is therefore constantly supressed and leads the body to believe it is overweight
• Encourages the individual to reduce their food intake

AO2

• Aphagia research: Damaged LH stops the feeling of hunger and leads to less feeding in rats (Anand & Brobeck, 1951)
• However, no dmaged LH has been found in post-mortems of AN sufferers
• Simplistic: Suggests that te LH has to be damaged, however it could be the other way round

Prenatal

• Hypoxia (a lack of oxygen) during birth can cause complications
• As well as this, infections during pregnancy can affect the brain development of the feotus, particularly in the 2nd trimester

AO2

• Favaro et al (2006): Found a significant association with risk of developing AN and obstructionn of the blood supply in the placenta
• Eagles et al (2001): Thought people with AN are more likely to hav had their 2nd trimester in the winter which would expose them to more infections
• Additionally, AN sufferers tend to have older siblings, more children during pregnancy= more exposure to infections

AO2

• Reductionism
• Can't explain AN sufferers experiance of body distortion
• Implies that anorexics are never hungry, eve though they often cite hunger as a motivation in continuing to starve themselves
• Suggests that it is more to do with a maladaptive response to hunger
• Alternative Approaches
• Dramatic increase of AN suggests environmental factors would better explain it
• For example, behavioural/SLT approach
• Role models are famed for thin bodies
• Vicarious reinforcement
• Cross-culturally, rates are dramaticallt different which siggests that it is environmental
• On the other hand, difference could be due to a difference of doctore's ability to diagnose it