Biological Explanations of Anorexia Nervosa

Less than 85% below normal body weight
Failure to lose weight leads to anxiety
Body perception distorted
Dry skin, dehydration, malnutrition, brittle nails, thinning hair, amenorrhea and fine hair growth
90-95% female
90% severe cases start at 13-18 years

DNA inherited from biological parents
Affects approximately 0.5-1% of population
Families with one relative with disorder - 4-5% chance

55% MZ twins concordance rate much higher than DZ twins 7%

Concordance rate not 100% - external factors

Neurotransmitter serotonin may be linked to AN
Linked to depression and OCD
Studies suggest serotonin levels low in AN

PET scans of brain show fewer serotonin receptors in brains of people with AN

Serotonin levels cause or effect?
Low level of receptors could be long term complication of AN
People with Anorexia do still feel hungry

Adapt to flee famine hypothesis
Anorexia behaviour adaptive 2 million years ago
AN = restless and higher levels of activity
Higher activity levels and denial of hunger help to migrate

No direct evidence
Refusal of food = death
One person with anorexia may be beneficial for everyone else

Psychology as a science - unfalsifiable
Reductionist - Simplify complex human behaviour
Nature/nurture - Focus on biological causes of behaviour
Gender bias - Most research carried out on females