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.
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.
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.
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|