Pressure to look like a super model may not be the only reason some young women fall victim to the eating disorder known as anorexia nervosa. In a large study of Swedish twins, researchers say the disorder appears to be moderately linked to heredity, and to neurotic behavior early in life among women.
Anorexia nervosa (AN), an eating disorder characterized by an extreme fear of obesity and an aversion to food, is associated with the highest death rate of any mental disorder, according to background information in the researchers article, which appears in the March issue of Archives of General Psychiatry, one of the JAMA/Archives journals.
A previous study reports that the number of new cases of anorexia increased during the past century and leveled off in the 1970s. Despite the seriousness of anorexia, little is known about risk factors for its development.
Cynthia M. Bulik, Ph.D., of the University of North Carolina at Chapel Hill, and colleagues studied individuals in the Swedish Twin Registry to examine the prevalence, heritability and risk factors for anorexia.
In 1972 and 1973, all participants in the registry answered a questionnaire gathering information about demographics, health and social circumstances. For the current study, the researchers focused on the 31,406 twins in the registry who were born between Jan. 1, 1935, and Dec. 31, 1958. During a four-year period ending in 2002, the twins were screened for a range of disorders, including anorexia.
The overall prevalence of anorexia in 2002 was 1.2 percent in women and .29 percent in men. The researchers estimate that the disorder is 56 percent heritable, with the remaining differences caused by environmental factors.
Those in the study born after 1945 had a higher prevalence of anorexia than those born before. Individuals who had lifetime anorexia reported having a lower body mass index (BMI; weight in kilograms divided by height in meters squared), exercising more and having better overall health satisfaction than those without anorexia. Those with a history of anorexia were at a lower risk of being overweight.
Using information from the questionnaires given in 1972 and 1973, the researchers examined seven potential predictors of anorexia among women:
• BMI,
• stomach problems,
• excessive exercise,
• perceived stress,
• an extroverted personality and neuroticism, characterized by low self-esteem,
• emotional instability and
• feelings of depression, anxiety and guilt.
Of these, only neuroticism was identified as a risk factor for subsequent anorexia.
"In conclusion, the prevalence of AN increased in both sexes between 1934 and 1958, while consistently afflicting females disproportionately," the authors write.
"Individuals with a history of AN appear to be protected from the development of overweight later in life. Anorexia is a moderately heritable psychiatric disorder that may be predicted by the presence of early neuroticism."
