Anorexia nervosa Biological explanations

EVOLUTIONARY THEORY OF ANOREXIA NERVOSA Guisinger 2003 Suggested that AN was an adaptive behaviour in the environment of evolutionary adaptation.

Hunter-gatherers had to move on regularly as food supplies in the local area were exhausted.

Guisinger notes that key characteristics of people with AN include restlessness and high levels of activity.

Whereas normal weight loss is accompanied by depression and inactivity.

Guisinger’s hypothesis High levels of activity and a denial of hunger help the individual to migrate in response to famine in their local area.

But This doesn’t explain why it affects more women than men.

Genes and anorexia nervosa Eating disorders seem to run in families.

But this doesn’t necessarily point to a genetic cause.

Holland’s study Compared MZ twins with DZ twins

Concordance rates for AN 55% MZ 7% DZ

Genetic predisposition Concordance rates are never 100% MZ twins may be treated more similarly than DZ twins

Methodological issues Looking identical does not necessarily ensure that twins are MZ.

Neural factors Kaye et al, 2005 Found a reduction in levels of the serotonin metabolite 5- HIAA in people with eating disorders.

This suggests that serotonin pathways are underactive. But these were early studies done on people who were currently suffering from anorexia at the time which made it impossible to be sure that the serotonin abnormality was the cause and not the effect.

PET Scans More recent technology help researchers to look at activity in the brain.

Kaye, 2005 PET scans show that are fewer serotonin receptors in the brain of people with eating disor.ders

Reduced serotonin receptors were reduced in people who had recovered from AN. However, this still does not conclusively prove that this was the cause. AN may have brought about long- term, even permanent changes.

Integrated approach Connan et al 2003 suggest an approach which combines biological and psychological factors.

Onset of AN is usually in adolescence which is a time of change and can be stressful

If the teenager is biologically prone to stress they may be more likely to respond to the stressors of puberty and adolescence in a maladaptive way. This could include an eating disorder.