April 16, 2006
Anorexia Nervosa 56% Genetic

Do not judge anorexics harshly. Their genes make them do it.

CHAPEL HILL – A new study led by University of North Carolina at Chapel Hill researchers estimates that 56 percent of the liability for developing anorexia nervosa is determined by genetics.

In addition, the study found that the personality trait of "neuroticism" (a tendency to be anxious and depressed) earlier in life is a significant factor associated with development of the eating disorder later.

Anorexia nervosa is a psychiatric illness characterized by an individual’s refusal to maintain a minimally acceptable body weight, intense fear of weight gain and a distorted body image. It occurs primarily among females in adolescence and young adulthood and is associated with the highest mortality rate of any mental disorder.

People prone to depression and anxiety are more prone to anorexia nervosa. So would anti-depressants and/or anti-anxiety drugs reduce the incidence of anorexia?

This study is the first published in the medical literature to estimate how much liability for developing anorexia nervosa is due to genetics, and the first to find a statistically significant association between the prospective risk factor of neuroticism and later development of anorexia, said Dr. Cynthia M. Bulik, lead author of the study, published in the March issue of the Archives of General Psychiatry.

"What this study shows is that anorexia nervosa is moderately heritable and may be predicted by the presence of early neuroticism, which reflects proneness to depression and anxiety," Bulik said. "Fifty-six percent heritability – that’s a fairly large contribution of genes. The remaining liability is due to environmental factors."

Bulik is the William R. and Jeanne H. Jordan distinguished professor of eating disorders in UNC’s School of Medicine and director of the UNC Eating Disorders Program at UNC Hospitals. She also is a professor of nutrition, a department housed in the schools of public health and medicine, and holds the only endowed professorship in eating disorders nationwide.

The reason she and her co-authors reached these conclusions where previous studies could not, Bulik said, is that their study was based on data obtained from screening a very large sample of twins. Their sample, from the Swedish Twin Registry, consisted of 31,406 individuals born between 1935 and 1958. None of the previous studies had samples nearly as large, Bulik said.

Twin studies continue to produce a wealth of scientific information about the human heredity.

The US National Institute for Mental Health says the death rate from anorexia nervosa is pretty high.

An estimated 0.5 to 3.7 percent of females suffer from anorexia nervosa in their lifetime.

The mortality rate among people with anorexia has been estimated at 0.56 percent per year, or approximately 5.6 percent per decade, which is about 12 times higher than the annual death rate due to all causes of death among females ages 15-24 in the general population.

But a March 2003 Mayo Clinic study found that the death rate from anorexia nervosa is no higher than among the general population.

ROCHESTER, Minn. — A long-term study of patients in Rochester, Minn., with the eating disorder anorexia nervosa found that their survival rates did not differ from the expected survival rates of others of the same age and sex.

The results, published in the March issue of Mayo Clinic Proceedings, add to the knowledge of anorexia nervosa and point to other areas that need greater study from researchers.

“Although our data suggest that overall mortality is not increased among community patients with anorexia nervosa in general, these findings should not lead to complacency in clinical practice because deaths do occur,” says L. Joseph Melton, III, M.D., Mayo Clinic epidemiologist and an author of the report.

One argument for the cause of the discrepancy is that other studies used anorexia nervosa sufferers who were sick enough to require hospitalization. Whereas a larger set of all anorexia nervosa sufferers as the Mayo Clinic used brings in people who have less severe cases.

The Mayo Clinic also has a public health information web page that claims anorexia does cause a high mortality rate.

Anorexia typically has numerous complications. At its most severe, it can be fatal. Anorexia has one of the higher deaths rates among all mental illnesses, hovering around 5 percent but perhaps even higher than that.

Perhaps some anorexia patients have such severe symptoms that they damage their bodies through malnutrition while other anorexia patients end up eating more like calorie restriction dieters and perhaps even gain some life expectancy as a result. Though that seems unlikely since the calorie restrictionists try hard to make sure they get enough vitamins, minerals and other essential nutrients aside from calories. Whereas I doubt the bulk of anorexia sufferers manage to do that.

Share |      Randall Parker, 2006 April 16 10:35 AM  Brain Appetite


Comments
lulu said at April 16, 2006 2:10 PM:

Randall,

Thi is the kind of research that should trigger sirens when reported. The assertion is incredible given that the stats are ambiguous - we have a correlation. A stat sign here is a crock. Without clear biomarkers I would ask this researcher to qualify the results heavily (15 minutes of fame is not the objective of science).

Laika the space dog said at April 25, 2006 12:46 AM:

As these things seem purely fashion statements, presumably there'll be a study next year saying that 59% of 'self harmers' are compelled to it by genetic factors. Where are these anorexics in previous eras or in different cultures? Anorexia seems to have far more in common with a sudden, inexplicable generational lust for David Cassidy or Donny Osmond than any genuine 'disease' and is just as dated.

Why does everything have to be medicalised these days? No-one does anything stupid or immoral, everyone's addicted to their vice and so it isn't their fault because addiction is somehow genetic rather than a choice. This is profoundly enslaving. Instead of people having the social stigma of shame helping them to refrain from harmful behaviour they're now encouraged to do it by a credulous media and parasitic therapy culture. Instead of people believing they have the power to change their behaviour they're told they're helpless victims of the horror de jour. It's not compassion, it's slavery.

I just don't believe a word of it. How is it that the vast majority of anorexic girls grow out of it in their 20s and are then perfectly normal? How can one grow out of a genetic complaint? How is it they're largely middle class girls in the developed west who suddenly rebel against high expectations and sexuality in their teens? It's like arguing that boys who shut themselves in their rooms in Japan do so for genetic reasons. Kids are bombarded with stories, most of them telling them they're too fat, others saying they're too thin. No wonder we grow up with mixed up ideas about food.

Everything's a threat these days. The weather is seen as some evil force imperilling us all, food is dangerous with every bite about to give you cancer, make you fat or see you waste away. The sun can kill you. Sex can kill you. It's all nonsense. People enjoy longer, healthier lives than ever before but the conquest of major disease through modern medicine, good living conditions and sanitation has just made us panic over perfectly normal things and invent diseases which don't actually exist.

Spiffy said at December 15, 2011 8:33 PM:

I was treated for anorexia at Mayo's Methodist hospital at the end of 1975. I am sure I was counted as one of their recoveries because I was at a healthy weight( and then some) within a couple years after treatment. After they stopped inquirying about me though, the anorexia and eating disorder returned. I was hospitalized again at least a dozen more times. No one in my family would consider me now cured. I would say now I'm a restricter and obsessive compulsive. Mayo's data may be faulty.

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