Causes:

There is no single cause for eating disorders. Although concerns about weight and body shape play a role in all eating disorders, the actual cause of these disorders appear to result from many factors, including cultural and family pressures and emotional and personality disorders. Genetics and biologic factors may also play a role.

Negative Family Influences

Negative influences within the family may play a major role in triggering and perpetuating eating disorders. Some studies have produced the following observations and theories regarding family influence.

• Parental Behaviors or Attitudes. Poor parenting by both mothers and fathers has been implicated in eating disorders. One study found that 40% of 9- and 10-year-old girls trying to lose weight generally did so with the urging of their mothers. A maternal history of eating disorders can be a factor in development of eating disorders in young girls, while paternal criticism of weight can lead to bingeing and purging in young males.
• Family History of Addictions or Emotional Disorders. Studies report that people with either anorexia or bulimia are more likely to have parents with alcoholism or substance abuse than are those in the general population. Parents of people with bulimia appear to be more likely to have psychiatric disorders than parents of patients with anorexia.
• History of Abuse. Women with eating disorders, particularly bulimia, appear to have a higher incidence of sexual abuse. Studies have reported sexual abuse rates as high as 35% in women with bulimia.
• Family History of Obesity. People with bulimia are more likely than average to have an obese parent or to have been overweight themselves during childhood.

The most positive way for parents to influence their children's eating habits and to prevent weight problems and eating disorders is to have healthy eating habits themselves.

Genetic Factors

Anorexia is eight times more common in people who have relatives with the disorder, and some doctors believe that genetic factors are the root cause of many cases of eating disorders. Twins had a tendency to share specific eating disorders (anorexia nervosa, bulimia nervosa, and obesity). Researchers have identified specific chromosomes that may be associated with bulimia and anorexia. In particular, regions on chromosome 10 have been linked to bulimia as well as obesity. Some evidence has reported an association with genetic factors responsible for serotonin, the brain chemical involved with both well-being and appetite. Researchers have also pinpointed certain proteins such as brain-derived neurotrophic factor (BDNF). This protein may influence an individual's susceptibility to developing an eating disorder.

Cultural Pressures

The approach to food in Western countries is extremely problematic. Enough food is produced in the U.S. to supply 3,800 calories every day to each man, woman, and child, far more than are needed for good nutrition. Obesity is a global epidemic, and few people living in this over-fed and sedentary culture eat a meal guiltlessly.

One interesting anthropologic study reported the following observations:

• During historical periods or in cultures where women are financially dependent and marital ties are stronger, the standard is toward being curvaceous, possibly reflecting a cultural or economic need for greater reproduction.
• During periods or in cultures where female independence has been possible, the standard of female attractiveness tends toward thinness.

The response of the media to the cultural drive for thinness and the overproduction of food both likely play major roles in triggering obesity and eating disorders.

• On the one hand, advertisers heavily market weight-reduction programs and present anorexic young models as the paradigm of sexual desirability.
• Clothes are designed and displayed for thin bodies in spite of the fact that few women could wear them successfully.
• On the other hand, the media floods the public with attractive ads for consuming foods, especially "junk" foods.

Hormonal Abnormalities

Hormonal abnormalities are common in eating disorders and include chemical abnormalities in the thyroid, the reproductive regions, and areas related to stress, well-being, and appetite. Many of these chemical changes are certainly a result of malnutrition or other aspects of eating disorders, but they also may play a role in perpetuating or even creating susceptibility to the disorders.

The primary setting of many of these abnormalities originate in a small area of the brain called the limbic system. A specific system called hypothalamic-pituitary-adrenal axis (HPA) may be particularly important in eating disorders. It originates in the following regions in the brain:

• Hypothalamus. The hypothalamus is a small structure that plays a role in controlling our behavior, such as eating, sexual behavior and sleeping, and regulates body temperature, emotions, secretion of hormones, and movement.

• The pituitary gland. The pituitary gland is involved in controlling thyroid functions, the adrenal glands, growth, and sexual maturation.
• Amygdala. This small almond-shaped structure lies deep in the brain and is associated with regulation and control of major emotional activities, including anxiety, depression, aggression, and affection.

Stress Hormones. The HPA systems trigger the production and release of stress hormones called glucocorticoids, including the primary stress hormone cortisol. Chronically elevated levels of stress chemicals have been observed in patients with anorexia and bulimia. Cortisol is very important in marshaling systems throughout the body (including the heart, lungs, circulation, metabolism, immune systems, and skin) to deal quickly with any threat.

Release of Neurotransmitters. The HPA system also releases certain neurotransmitters (chemical messengers) that regulate stress, mood, and appetite and are being heavily investigated for a possible role in eating disorders. Abnormalities in the activities of three of them, serotonin, norepinephrine, and dopamine, are of particular interest. Serotonin is involved with well-being, anxiety, and appetite (among other traits), and norepinephrine is a stress hormone. Dopamine is involved in reward-seeking behavior. Recent research suggests that people with anorexia have increased activity in the brain's dopamine receptors. This overactivity may explain why people with anorexia do not experience a sense of pleasure from food and other typical comforts.

Ghrelin. High levels of ghrelin, a hormone that increases the feeling of hunger and slows metabolism, have been noted in patients with anorexia and bulimia.

Low Levels of Reproductive Hormones. The hypothalamic-pituitary system is also responsible for the production of important reproductive hormones that are severely depleted in anorexics. Although most doctors believe that these reproductive abnormalities are a result of anorexia, others have reported that in 30 - 50% of people with anorexia, menstrual disturbances occurred before severe malnutrition set in and remained a problem long after weight gain, indicating that hypothalamic-pituitary abnormalities may precede the eating disorder itself.