Biological Explanation for Anorexia

• What is biological explanations for AN split into?

  • Genetic
  • Neural
• What is anorexia nervosa?

  Eating disorder characterised by obsessive desire to lose weight by refusing to eat
• Twin studies (genetic)

  MZ twins found to have higher concordance rate than DZ

  • They have a moderate to high heritability of AN varying between 28% to 74% - Thornton

  Holland et al - concordance rate for AN with MZ of 56% and 5% for DZ

  ---> suggesting there's a link between twins and AN
• Family studies(genetic)

  First degree relatives (parents, siblings, children) of ind with AN are approximately 10x more likely to develop AN - Strober et al
• Adoption studies (genetic)

  Klump et al - studied adopted sibling pairs and some biological sibling pairs for disordered eating symptoms

  • Found heritability from 59% to 82% - shows environment also plays factor
• Strength/ limitation of genetic explanations

  Supporting evidence - use any of case. H/e

  
  

  Weak body of evidence

  Most studies rely on concordance and heritability rates

  If AN is solely genetic concordance in MZ would be 100%

  Meaning results are inconsistent - decreases reliability
• Limitation of genetic explanation

  Lack of conclusive evidence

  Actual heritability of disorder is unknown - no conclusive genes identified

  + Identical & non identical twins may not be raised in same environment

  Decreases validity - doesnt truly reflect genetic contribution to AN
• What does neural explanations suggest?

  AN results from abnormally functioning brain mechanisms & functions
• Serotonin

  Bailer et al - serotonin is linked with maintenance of AN because of its link to anxiety; as reducing eating also reduces serotonin

  
  

  High level of serotonin = feel need to not eat because they realise it makes them feel better emotionally due to reduction in serotonin
• Dopamine

  As dopamine activity increases in basal ganglia, it appears to alter the way ind interpret rewards - Kaye et al

  High dopamine = difficult to associate positive feelings with pleasurable acts e.g. eating food
• Insula dysfunction hypothesis 


  Insula brain area is part of cerebral cortex - develops different for ind with AN

  • Hypothesis arose from observation that many symptoms of AN are associated with dysfunction in several brain areas all connected to insula
• Strength/ limitation of neural explanation

  Empirical support

  • Kaye et al - elevated serotonin activity in AN ind, which may contribute to increase anxiety which decreases appetite
  • Bailer et al - observes altered dopamine function in AN ind, explains reduced sensitivity to food

  H/e most research relies on correlations ---> unclear if its altered ser/dop or starvation - decreases validity
• Strength of neural explanations

  Practical application

  Understanding has led to advancements in treatment e.g. use of SSRI to regulate serotonin levels = reduces symptoms like anxiety

  Increases validity
• Limitation of neural explanation

  Biologically reductionist

  Ignores social and cultural influences focuses solely on biology

  • e.g. body image pressures or family dynamics

  Oversimplifies complexity of disorder