Introduction

Chapter 1: Defining Eating Disorders

Chapter 2: Soical Precipitants

Chapter 3: Psychological Precipitants

CHAPTER FOUR: BIOLOGICAL PRECIPITANTS

Hypothalamic dysfunction is seen in anorexia.  The question is whether this condition is secondary to malnutrition, or if there is a primary hypothalamic condition which precipitated the eating disorder.  If hypothalamic dysfunction exists prior to the onset of illness, it might very well depress the appetite such that the individual would cease eating and take on a cachectic appearance.  This condition is reversible upon re-feeding and weight gain.

Hypoglycemia, which causes carbohydrate craving and feelings of hunger, is a medical complication resulting from bingeing.  However, if it existed prior to the illness, this could explain the frenetic binge-purge behavior of the bulimic.

Though experts continue to search for a primary organic precipitant to eating disorders, the literature strongly leans towards these biological anomalies as secondary to the manifestations of eating disorder (Bryant-Waugh and Lask, 1992).

Genetics

Research using studies of twins and families indicate the significance of genetics in the development of eating disorders.  Jones and Nagel mention several such studies in their literature.  One study by Holland et al (1988) took a sample of 45 twin pairs and found that of the non-identical sets only 5% both had anorexia nervosa, and of the identical sets, 56% were both found to share the disorder.  A similar study described by Crisp et al (1985) of 30 pairs of twins, showed a concordance rate of 7% among non-identical twins, and 55% among identical twins.  Interestingly, when sisters were studied, concordance rates were much lower, between 3% and 10% (Jones and Nagel).

Family studies indicate a higher incidence of anorexia among first- and second-degree relatives of anorexic patients, but similar correlations have not been found of bulimics (Jones and Nagel).

Jones and Nagel cite several studies on the correlation between affective disorders and eating disorders.  All the literature reported similar findings in that over 50% of the mothers of anorexics had a history of depression.  No correlation of this kind could be made of the purely bulimic population.

Thus far, it has been difficult to establish clear-cut data regarding the physiological causes of an eating disorder.  Since patients present for treatment after their illness has been in full swing for some time, physicians often have no base-line data on these patients prior to illness.  In regards to the family and twin studies, there have been no comparisons between twins raised together and apart, which might tie in the important psychological aspects of environmental influences.  As yet, researchers are not drawing definitive conclusions about the potential biological precipitants of eating disorders.  Most will agree that this aspect requires further research and that psychological and socio-cultural influences are the primary precipitants of eating disorders.

Next: CHAPTER FIVE COMPLICATIONS