biological explanation of anorexia - genes

• Gene


  A carrier of information that contains a set of instructions and is responsible for our development
• Genes

  • Made up of DNA
• Twin and adoption studies

  Can be used to investigate the effect of nature and nurture on behaviour
• MZ twins

  Share 100% of their genes
• DZ twins

  Share 50% of their genes
• Concordance rate


  Can be measured to determine if behaviour is genetic
• The influence of genes has been inherited from biological parents
• Anorexia

  If genes are an explanation, the frequency of anorexia in relatives of someone with it should be higher than in the general population
• Identical twins

  Should be more concordant than non-identical twins for anorexia
• Kipman's research found a heritability estimate of 71% for anorexia when looking at the concordance rate of MZ and DZ twins
• Fairburn and Harrison found a 55% concordance rate for MZ and 5% concordance rate for DZ twins for anorexia
• Twin studies

  • Provide strong genetic evidence from concordance rates which are objective and measurable
• Twin studies

  • Ignore the role of environmental factors in causing anorexia, the environment must play a role because the concordance rates for MZ twins were not 100%
• Heritability estimates can be made using families and twin studies
• If genes can explain anorexia, it may be something about the disorder itself that is similar or the same between relatives rather than other features such as depression
• Wade et al's research found that perfectionism (a high need for order and sensitivity to praise) were linked to anorexia
• Bachner-Melman found that three of the genes implicated in anorexia are also associated with perfectionism personality traits
• Grice et al followed 192 families where one member had received a diagnosis, and found a genetic link on chromosome 1 in multiple family members, with first degree relatives being 7 times more likely to have an eating disorder
• The EPHX2 gene codes for an enzyme which regulates cholesterol metabolism, serotonin levels, and parts of the brain for eating such as the hypothalamus and amygdala
• The ITPR3 gene codes for a protein involved in detecting the taste of food such as bitterness and sweetness, and if faulty could mean they are unable to use food as a motivator to eat
• Specific genes

  • Drug therapies may be effective e.g. antipsychotics target serotonin which may help with the EPHX2 gene
• Specific genes

  • Do not entirely explain the genetic cause so doesn't treat the root cause, only helps with comorbid factors
• The diathesis stress model best accounts for the influence of nature and nurture and is the most holistic approach
• The individual may inherit a vulnerability to the disorder (e.g. through particular genes) but the development of the disorder is due to psycho-social stressors