Anorexia Nervosa: Bioloigcal Explanations

Question 1

Clinical characteristics

Answer 1

• persistent restriction of food intake
• intense fear of gaining weight
• disturbed by own body shape size

Question 2

Two sub-types of anorexia

Answer 2

• restricting and binge-eating/purging

Question 3

Biological explanation: stats

Answer 3

• rare, but more prevalent -> 0.3% male, 0.9% female
• 90% cases female
• 30-40% will show no response to treatment after 5 years
• mortality rate of 8% -> suicide

Question 4

Twin studies

Answer 4

• Holland et al: studied 45 pairs of female twins, and found a concordance rate of 56% for MZ twins but only 5% for DZ twins
• study replicated several years later by Treasure and Holland with 65% for MZ twins and 32% for DZ twins
  -> identical twins feel the need to look the same in terms of their physical features
  -> MZ twins share the same pre-disposed gene that leads them to both developing anorexia

Question 5

Family studies

Answer 5

• Strober: first degree relatives of individuals with AN have approximately 10x greater lifetime risk of having AN than relative of unaffected individuals
• Tozzi et al: research suggests that there is an increased risk of developing other eds in relatives of individuals diagnosed with AN, suggesting that people may inherit a more general vulnerability to eds rather than AN specifically

Question 6

Adoption studies

Answer 6

• Klump et al: 123 adopted sibling pairs, and 56 biological sibling pairs
• because of the low prevalence of AN, disordered eating symptoms were assessed instead
• heritability estimates ranged from 59% to 82% for the different aspects of disoredered eating, with non-shared environmental factors accounting for the remaining variance

Question 7

Candidate Genes

Answer 7

• Scott-Van Zealand et al: cadidiate gene association study, 1205 AN with 1948 control by sequencing 152 candidate genes believed to be linked to AN
• Ephx2 was significantly associated with it
• codes for an enzyme involved in cholesterol metabolism
• many people in acute phase of AN have abnormally high levels of cholesterol

Question 8

Why might candidate genes be an over simplification

Answer 8

• deterministic, having this gene doesn’t guarantee someone will have anorexia, an issue between cause and effect

Question 9

Genome wide association studies (GWAS)

Answer 9

• Boraska et al: conducted 5551 with 21080 matched controls
• 72 genetic variations were identified but none significantly related to AN
• argued that not because genetic influences on AN are non-existent but because their study was not sensitive enough to detect them

Question 10

Neural explanations

Answer 10

• dysfunctions in serotonin and dopamine

Question 11

Bailer and Kaye

Answer 11

• low levels of serotonin breakdown by-products in people with AN.
• levels return to normal after short-term weight recovery and increase above normal levels after long term recovery
  -> suggests that people with AN start off with too much serotonin, suppress appetite to control levels of anxiety and obsessiveness in an attempt to lower serotonin levels