Recently this model, Gisele Bundchen, speculated that the fashion industry is not to blame for anorexia. Rather parents are to blame:

Gisele Bundchen has entered Brazil's growing debate over anorexia, saying families are to blame _ not the fashion industry.

"I never suffered this problem because I had a very strong family base," the supermodel told the local Globo newspaper on Friday. "The parents are responsible, not fashion."

Top model Giselle Bundchen wears a creation part of the Colcci fall-winter fashion collection during the Fashion Rio 2007, in Rio de Janeiro, Friday, Jan 19, 2007.

The 26-year-old model was in Brazil for the annual Fashion Rio, a weeklong showcase for some of the country's top designers.

Anorexia became a hot issue in Brazil after the deaths of four young women last month, including 21-year-old model Ana Carolina Reston.

This statement made me think several things:

1) When did we start listening to models?

2) Right. I'm sure that squeezing into a size -10 dress or else you lose you job had nothing to do with it.

3) Actually, the issue is more complicated. Anorexia is primarily a genetic risk with an environmental trigger.

The evidence for this I will get to in a second, but some eating disorders researchers issued a statement clarifying -- in case you didn't already know -- that Ms. Bundchen has no idea what she is talking about:

Misstatements and ignorance claiming that families "cause" eating disorders is like blaming parents for diabetes or asthma or cancer says an international group of eating disorders researchers. Recent damaging statements by fashion model Gisele Bundchen stating that unsupportive families cause anorexia nervosa only perpetuate misconceptions and further stigmatize eating disorders. Contrary to her claim, there is no scientific evidence that families cause anorexia nervosa. In fact, the researchers are finding that anorexia nervosa is far more complex than simply wanting to be slim to achieve some fashionable slender ideal. The data show that anorexia nervosa has a strong genetic component that may be the root cause of this illness.

"An uninformed opinion such as Bundchen's causes harm on a number of levels. By contributing to the stigma, it drives sufferers underground and creates obstacles to seeking help. It damages attempts at advocacy and hurts parents who are desperately fighting for their child's recovery," said Allan S. Kaplan, M.D., Loretta Anne Rogers Chair in Eating Disorders at the University of Toronto. "Such thinking also misinforms third party payors who may not want to pay for the treatment of these biologically-based illnesses if they think its primary cause is family dysfunction."

Dr. Kaplan is a member of the international group of researchers attempting to find which genes contribute to anorexia nervosa through a National Institute of Mental Health-funded study of families with a history of anorexia nervosa. The current study, which is being conducted at 10 sites across the world, hopes to further clarify which genes play a role in anorexia nervosa. The study builds on data from ten years of groundbreaking research on the genetics of eating disorders sponsored by the Price Foundation.

"We often hear that societal pressures to be thin cause many young women and men to develop an eating disorder. Many individuals in our culture, for a number of reasons, are concerned with their weight and diet. Yet less than half of 1 percent of all women develop anorexia nervosa, which indicates to us that societal pressure alone isn't enough to cause someone to develop this disease," said Walter H. Kaye, M.D., professor of psychiatry, University of Pittsburgh School of Medicine. "Our research has found that genes seem to play a substantial role in determining who is vulnerable to developing an eating disorder. However, the societal pressure isn't irrelevant; it may be the environmental trigger that releases a person's genetic risk." Families should not be blamed for causing anorexia. In fact, they are often devastated and suffer from the consequences of this illness." (Emphasis mine.)

What is the genetic risk associated with anorexia? Well, we know from twin studies that the heritability of anorexia is about 55% -- quite high for a psychological disorder. The shared environment component of that -- the part of the risk that the twins get from shared environment, read: parents -- is only about 5%. This leaves a large area for unique environment which in this studies means essentially random components of the environment that the parents cannot control. (For information about how to interpret heritability estimates, read this.)

This pattern is characteristic of a variety of psychiatric disorders. The issue is partly genetic. But the issue also has to do with factors in the environment that cause people to express that genetic risk. This explains the rise in the prevalence of anorexia since 1945.

The nature of the genetic risk factor specifically is not clear, but it probably has to do with anxiety. Anorexics also have a high probability of being neurotic (not in the Freud sense, but in the personality inventory sense). This tendency to anxiety probably explains how a normal desire to be at a healthy wait turns into a pathological desire to be too thin.

There are certainly some overbearing parents out there, but that is not the whole story.