Biological Explanations for Anorexia Nervosa

Anorexia Nervosa (AN)

• Anorexia fits into one of three categories of eating disorders.
• An eating disorder is a maladaptive or a dysfunctional relationship with food.
• It symptoms appear in 4 different types; physical, cognitive emotional and behavioural.
• It is characterised by 4 criteria set out by the DSM iv (Diagnostic and Statistical Manual of Mental Disorders). These are:

1. Anxiety; the fear of being fat.

2. Weight; weight drops below average. 

3. Body Image distortion; they see their weight and shape as distorted.

4. Amenorrhoea; the stopping of the menstrual cycle.

Neural Explanations 

Neurotransmitters - A01; Changes in the levels of the neurotransmitter serotonin appear to be characteristic of individuals with eating disorders. Bailer (2007) compared serotonin activity in women recovering from restricted eating and binge eating . They found higher serotonin levels in women who were recovering from binge eating than the women who were recovering from restricted eating. They also found that the highest levels of serotonin activity in women showed the most anxiety. This suggests that persistent distribution of serotonin levels may lead to increased anxiety which may then lead to AN. 

A02; There is a problem with this explanation. SSRI's alter levels of available brain serotonin. These are ineffective when used with AN patients. However, Kaye (2001) found that when used with a recovering AN patient, these drugs were effective in preventing relapse. 

Neural Explanations

Neurotransmitters - A01; Recent studies suggest a role for dopamine in AN. Kaye (2005) used a PET scan to compare dopamine activity levels in the brains of 10 women recovering from AN and 12 healthy women. In the AN women, they found overactivity in dopamine receptors in a part of the brain known as the basal ganglia. People with AN find it difficult to associate good feelings with the things that most people find pleasurable, in this case that would be food. 

A02; There may be problems with thi explanation, Castro-Fornieles (2006) found that adolescent girls with AN had higher levels of homovanillic acid than a control group. Improvement in weight levels was associated with normilisation of homovanillic levels. Research has shown lower than normal levels of dopamine recptors in obese individuals, Levels of dopamine seem to be related to levels of body weight. 

Pregnancy and Birth Complications

A01; Lindberg and Hjern (2003) found a significant association between premature birth and and the development of AN. Birth complications may lead to brain damage caused by lack of oxygen, impairing the neurodevelopment of a child. Nutritional factors may be impaired if the mothers have an eating disorder. Bulik (2005) suggests that mothers with AN expose their offspring to a 'double disadvantage'. 

A02; There are obsteric (problems during childbirth) complications with this study. A recent prospective birth study provides support for the obsteric complications. Favaro (2006) found that perinatal (time or after of the birth) complications significantly associated with the risk of developing AN were placental infarction (obsturcted blood supply in the placenta). This suggests that AN is associated with early eating difficulty. 

Season of Birth

A01; Research suggests that individuals with AN are more likely to have been born within spring months. Explanations for this include intrauterine (withing the uterus) infections during pregnancy and tempreture at time of conception. One study found that among patients with AN in equatorial regions of the world there was no seasonality effect in the development of AN.

A02; There may be a problem with this explanation. Eagles found that anorexic individuals tend to be later in birth order compared with healthy individuals. The more siblings a child has when it is still in the womb, the more likely the mother is going to be exposed to common infections, and the more likely that this will be passed on to the unborn child. The critical period for brain development is the second trimester of pregnancy, so for a spring birth the second trimester would occur at the time of the year when infections are most likely (winter). 

The Reproductive Suppression Hypothesis

A01; Subrey (1987) suggests that adolescent girls desire to control their weight represents an evolutionary adaptation in which ancestral girls delayed the onset of sexual maturation in response to to cues about the probability of poor reproduction success. The ability to delay reproduction is adaptive. This model is based on the observation that puberty is delayed in females when they are subjected to stress or are in poor physical condition.

A02; There are many problems with the reproduction suppression hypothesis. The hypothesis is supported by the observation that the onset of puberty is delayed in prepubertal girls with AN. This means that reproduction is effectively suspended in anorexic females.  

The 'Adapted to Flee' Hypothesis (AFFH)

A01; The AFFH (Guisinger) suggests that the typical AN symptoms of food, hyperactivity and denial of starvation reflect the operation of adaptive mechanisms that once caused migration in response to local famine conditions. Food restriction is a common feature of many species when feeding competes with other activities such as migration or breeding. 

A02; There are treatment implications for AFFH. Guisinger claims that the AFFH relieves therapists of the need to search for famial reasons for AN. A struggle for control between those with AN and those who want to get better, is a characteristic of AN. 

A02; There are problems associated with the evolutionary explanation. We may question how the symptoms of AN might be passed on naturally, or be naturally selected. AN would have functioned more effectively in ancestrial conditions, yet outside the ecological setting in which it evolved disorders such as AN can be deadly.

A03; There is a gender bias with this research. Most studies of eating disorders concentrate on women even though 25% of people with an eating disorder are men. Because of this, studies can not be generalised to the whole population. 

A03; This approach can be classed as deterministic because it assumes that some people are predisposed to get AN.