Neural explanationNeural explanationand and

Evolutionary explanationsEvolutionary explanations

For Anorexia NervosaFor Anorexia Nervosa

Biological explanationsBiological explanations

• NeurotransmittersNeurotransmitters

- serotonin and - serotonin and dopaminedopamine

• NeurodevelopmenNeurodevelopmentt

Pregnancy and Pregnancy and birth birth complicationscomplications

Season of birthSeason of birth

• Evolutionary Evolutionary explanationsexplanations

- The reproductive - The reproductive suppression suppression hypothesishypothesis

- The adapted to - The adapted to flee hypothesis flee hypothesis (AFFH)(AFFH)

Neurotransmitters -Neurotransmitters -SerotoninSerotonin

Disturbances in these levels

Higher serotonin activity activity in women recovering from binge-eating/purging type anorexia.

Highest levels of serotonin activity in women who showed the most anxiety.

High levels of serotonin are associated with jittery, anxious feelings. In order to get rid of these anxious feelings – the person may stop eating.

Suggestion then, that it is the anxiety that triggers Anorexia and that AN is just a symptom of getting rid of the anxiety.

AO2 - serotoninAO2 - serotonin

• Issue in that people with AN when given Issue in that people with AN when given SSRI’s – makes no difference.SSRI’s – makes no difference.

• Only when used with recovering AN Only when used with recovering AN patients does it prevent relapse.patients does it prevent relapse.

• Lack of food may stop the SSRI’s from Lack of food may stop the SSRI’s from working – but then becomes successful working – but then becomes successful when food is put back into the body.when food is put back into the body.

DopamineDopamine

Pet scans

Comparison of dopamine activity in brains of 10 women recovering from AN and 12 healthy women.

Overactivity in dopamine receptors in the basal ganglia. This area dopamine plays a part in interpretation of harm and pleasure.

Increased activity alters the way in which people interpret rewards.

People with AN find it difficult to associate good feelings with what we normally derive pleasure in – eg food.

Dopamine – AO2Dopamine – AO2

• Support from adolescent girls who had Support from adolescent girls who had higher levels of homovanillic acid (waste higher levels of homovanillic acid (waste product of dopamine). product of dopamine).

• Improvement in weight levels associated Improvement in weight levels associated with homovanillic levels normalisingwith homovanillic levels normalising

• Obese individuals – had lower than normal Obese individuals – had lower than normal levels of dopamine receptors which levels of dopamine receptors which means that dopamine levels are perhaps means that dopamine levels are perhaps related somehow to body weight.related somehow to body weight.

NeurodevelopmentNeurodevelopment

PREGNANCY AND BIRTH COMPLICATIONS

Association between premature birth and AN

Brain damage through birth complications causing hypoxia impairing neurodevelopment of the baby.

If mother has eating disorder then baby not getting the nutrition needed.

Double disadvantage – as mothers transmit a genetic vulnerability to AN plus inadequate nutrition.

AO2 – obstetric AO2 – obstetric complicationscomplications

• Support from Favaro et al (2006) Support from Favaro et al (2006) perinatal complications perinatal complications significantly associated with risk of significantly associated with risk of developing AN – placental developing AN – placental infarction (obstructed blood supply infarction (obstructed blood supply in the placenta) and early eating in the placenta) and early eating difficulties and low birth weight.difficulties and low birth weight.

Season of birthSeason of birth

Individuals with Anorexia more likely to be born in spring time.

People will get infections in the 2nd trimester – time of year for getting them.

Infections such as intrauterine infection and high temperature.

Willoughby et al (2005) found no seasonality effect in the development of AN where it is hot all year round.

Season of birth – AO2.Season of birth – AO2.

• Support by Eagles et al 2005 – AN Support by Eagles et al 2005 – AN individuals are later in birth order individuals are later in birth order compared with healthy controls.compared with healthy controls.

• The more elder siblings the child has The more elder siblings the child has whilst in the womb the more likely the whilst in the womb the more likely the mother will be exposed to common mother will be exposed to common infections.infections.

• Critical period for brain development is Critical period for brain development is 22ndnd trimester. trimester.