Discuss biological explanations for anorexia nervosa
Introduction
Eating disorder. Associated with restricted food intake and therefore
extreme weight loss. Below average BMI. Based on a lack of control.
Typically affects young people. Cultural variety.
Course and outcome: 15-20% have single episode, get full remission,
never relapse. 15-20% experience in chronic unremitting way, high
mortality. 60% episodic. Get it – remission – relapse etc.
AO1 – Biological
Due to genes. Gene inherited. Gives pre-disposition to anorexia.
Studied using Twin studies:
Indentical = MZ = 100% DNA shared
Fraternal = DZ = 50% shared
Look at concordance rate
Or could be due to malfunction/structural defect in hypothalamus.
LH/VMH too low. Not triggering hunger until too late/triggering satiety
too quickly.
Could be neurotransmitter imbalance.
AO2 – Biological
Holland: Found 55% concordance rate for MZ twins compared with only 7%
concordance rate DZ.
Castro-Fornieles et al: Adolescent girls with AN had higher levels of
homovanillic acid (waste product of dopamine) than control group.
Improvement of weight linked with normalisation of levels.
X 45% discordance. 1 twin had it, other didn’t. Most likely not due to genes.
Environmental influence.
X Concordance rate for MZ may be higher as they’re treated more similarly.
Introduction
Eating disorder. Associated with restricted food intake and therefore
extreme weight loss. Below average BMI. Based on a lack of control.
Typically affects young people. Cultural variety.
Course and outcome: 15-20% have single episode, get full remission,
never relapse. 15-20% experience in chronic unremitting way, high
mortality. 60% episodic. Get it – remission – relapse etc.
AO1 – Biological
Due to genes. Gene inherited. Gives pre-disposition to anorexia.
Studied using Twin studies:
Indentical = MZ = 100% DNA shared
Fraternal = DZ = 50% shared
Look at concordance rate
Or could be due to malfunction/structural defect in hypothalamus.
LH/VMH too low. Not triggering hunger until too late/triggering satiety
too quickly.
Could be neurotransmitter imbalance.
AO2 – Biological
Holland: Found 55% concordance rate for MZ twins compared with only 7%
concordance rate DZ.
Castro-Fornieles et al: Adolescent girls with AN had higher levels of
homovanillic acid (waste product of dopamine) than control group.
Improvement of weight linked with normalisation of levels.
X 45% discordance. 1 twin had it, other didn’t. Most likely not due to genes.
Environmental influence.
X Concordance rate for MZ may be higher as they’re treated more similarly.
