Biological explanations for anorexia nervosa include neural explanations and evolutionary explanations. 1st BIOLOGICAL EXPLANATION - Neurotransmitters
Disturbances in the levels of the neurotransmitter serotonin appear to be a characteristic of individuals with eating disorders. Kaye 2005 found a reduction in the levels of the serotonin metabolite 5-HIAA in people with eating disorders. This suggests that brain serotonin pathways are underactive. Using PET scans it has been shown that there are fewer serotonin receptors in the brains of those with eating disorders. The brain serotonin system has been implicated in personality traits linked with eating disorders such as obsessionality, perfectionism, anxiety & depression. A reduction in receptors suggests a dysfunction of the serotonin system. Serotonin is also part of the neurotransmitter system of the hypothalamus that controls feeding behaviour. This neurotransmitter system of the hypothalamus is implicated in the cause of eating disorders. There is research supporting the role of serotonin in anorexia which was undertaken by Bailer et al 2007. Serotonin activity was compared in women recovering from restricting type anorexia & binge eating/ purging type with healthy controls. They found significantly higher serotonin activity in the women recovering from the binge-eating/purging type. In addition they found the highest levels of serotonin activity in women who showed the most anxiety, suggesting that persistent disruption of serotonin levels may lead to increased anxiety, which may trigger anorexia. Gender bias
It is however highly gender bias that alike this research most studies of eating disorders have concentrated on the study of women, but according to recent statistics, 25% of adults with eating disorders are men. Meaning that findings cannot be generalized to males and are therefore unable explain anorexia in males. -Dopamine
Recent studies suggest a role for dopamine in anorexia. Kaye et al 2005 used a PET scan to compare dopamine levels in the brains of 10 women recovering from anorexia, and 12 healthy women. In the anorexic women over activity in the dopamine receptors in the basil ganglia, (where dopamine plays a part in the interpretation of harm & pleasure) are cited for playing a role in anorexia. Increased dopamine activity in this area appears to alter the way people interpret rewards. Anorexics find it difficult to associate good feelings with the things most people find pleasurable (such as food). Food refusal can bring more pleasure. There is research support for the role of dopamine in anorexia. 12 healthy participants & 10 recovering anorexics were administered one dose of the drug amphetamine (which releases dopamine in the brain). PET scans were then used to visualize subsequent dopamine activity. In participants without an eating disorder the induced release of dopamine was associated with feelings of pleasure. Whereas, in the recovering anorexics, the release of dopamine made them feel anxious & activated the part of the brain that worries about consequence. This suggests there is an over activity in dopamine receptors. When individuals with anorexia eat, the release of the neurotransmitter makes them anxious rather than experiencing the normal feelings of reward. Research scientific / issue of cause & effect
There is clearly the research support for the role of serotonin and dopamine in AN, research which is of scientific nature, thereby giving validity. However cause & effect may pose problems with neural explanations. It is not clear if anorexia causes a disturbance in neurotransmitters or if this disturbance is an effect of anorexia. In anorexia loss of body weight itself produces hormonal & brain changes as the body tries to cope. Therefore it is not possible to suggest that neurotransmitters are the cause or an effect of eating disorders. The...