There is a lot of evidence that genetic factors are important in determining whether an individual is susceptible to the illness as there is an increased risk of a close relative to the sufferer also developing the disorder. Evidence from twin studies supports the idea of a genetic link. Holland (’88) studied anorexia in monozygotic (identical) and dizygotic (non identical) twins. It was found that there was a 56% concordance rate between monozygotic twins and only a 5% concordance rate for dizygotic twins. These findings suggest that because identical twins have the same genetic make up if one has the disorder there is a greatly increased chance of the other twin also developing it and that it is not only environmental factors in the family causing it. This is strong evidence to show genetic vulnerability but there must be other factors involved or identical twins would show 100% concordance. It is likely that the genetic vulnerability is triggered by an environmental factor that causes the individual stress. It is not possible to establish cause and effect in genetics research as only natural studies can be carried out so it is not possible to directly manipulate the independent variable. Greater concordance between monozygotic twins may be explained in terms of environmental factors, if twins look and behave alike then family members may treat them more similarly than if they were non identical twins. Genetic studies seem very successful in accounting for the disorder but they cannot explain the dramatic increase in recent years, it is unlikely that genetic factors would change so rapidly.
Anorexia has also been linked to abnormalities in the individual’s brain. It has been found that sixteen out of eighteen anorexics examined had reduced blood flow to parts of the brain governing appetite and a sense of fullness. This may account for anorexics’ distorted thinking about food. Psychologists have also used the hypothalamus to try and explain the disorder. Keesey and Corbett found that the lateral hypothalamus and the ventromedial hypothalamus work together to maintain weight homeostasis, if hypothalamic functioning was disturbed this may lead to the disorder. Anorexia leads to amenorrhoea and secretions of hormones governing sexual development are greatly reduced in anorexics. This may suggest that a problem with the pituitary gland and endocrine system offers an explanation. These explanations have not been very successful in accounting fro anorexia because post mortems of patients with eating disorders have not revealed lesions in the parts of the brain considered to have abnormalities. It is also not possible to establish whether the eating disorder leads to changes in the neuroanatomy of the brain rather than the other way round.
Another theory is that cognitive factors cause anorexia, it is suggested that eating disorders are the result of the individual having distorted beliefs about their image and food. Research has shown that anorexics think differently about their body, weight and food and this may explain their distorted eating patterns. Garfinkel and Garner (’82) found that anorexics typically overestimate body size. However, it is not clear whether distorted thinking causes anorexia or is the result of it. If thoughts are distorted before the onset of the disorder they may play a part in its development whereas if cognitive biases develop after the onset they cannot be a causal factor.
Psychoanalytic theory, put forward by Freud may explain how events in childhood may make people more likely to develop anorexia. In the oral stage of development the bond between mother and child is developed and may act as a model for later relationships. Feeding difficulties may be associated with hunger, discomfort and displeasure, later this stage in development may be revisited if the individual is experiencing conflict. This theory also suggests that traumatic early childhood experiences lead the adolescent to reject their body. The individuals have an unconscious desire to remain pre pubescent, by not eating they avoid growing into a sexually mature woman and independence will be avoided. It is very difficult to find evidence to support or refute this theory as it places emphasis on unconscious desires and repressed memories that cannot easily be retrieved. As a theory this is not so applicable to males although it may explain why homosexual males are more prone to the disorder because they may have difficulties coming to terms with their sexuality. It does not account for anorexia appearing after adolescence so as a theory it is not that successful in accounting for the illness.
The dramatic increase in anorexia nervosa in recent years can be explained by looking at the social learning theory. Cultural idealisation of the slender female figure as shown in the media may cause a girl to fear becoming fat. The importance of media influence was shown in a study by Hamilton and Walker (’93), who showed women with eating disorders and women without photographs of idealised bodies as portrayed in women’s magazines. The photographs did not affect women without eating disorders, whereas eating disordered women over estimated their body size more after seeing the photographs. Social factors may explain why people in certain occupations such as dancing and modelling are more prone to eating disorders, because there is a lot of pressure on them to be thin. In some non-western cultures instances of anorexia nervosa are much lower and instances are lower in black than in white populations. This suggests that in western cultures there is more pressure from the media to be thin and avoid being overweight. This theory is quite successful in accounting for why anorexia is more common in certain professions and cultures, why women are more affected by men and also shows why it has increased so dramatically in recent years. However, given that most women in western societies are exposed to slim attractive models, it does not explain why some develop the illness and others do not. Research between cultures may reflect different forms of diagnosis being used rather than different disorders.
It is unlikely that there is a single explanation that fully accounts for anorexia nervosa. As it is such a complex disorder it is likely that all the theories put forward offer some valid explanations for anorexia but some theories may be more relevant to different individuals than others. The strongest evidence from studies into anorexia seems to come from theories involving genetic and social factors. It is likely that when those individuals with a genetic susceptibility to the illness are exposed to environmental stressors such as social pressure the disorder will be triggered, as shown by the diathesis-stress model of abnormality.
