Lorraine Savage has been a writer and editor for more than twenty years. Her topics of interest include medical and healthcare, organic food and healthy eating, animals and petcare, biographies and history, science and environment, business and finance, and Japanese culture and comic books. She has worked on newsletters, newspapers, trade journals, magazines, non-fiction books, and websites
For years, doctors, sociologists and psychologists have debated the cause of eating disorders such as anorexia nervosa and bulimia. The generally held view was that eating disorders were mental illnesses that caused a young person, usually a woman, to try to gain control over her body by controlling what and when she ate. However, new studies into the human genome have revealed a physiological link between biology and eating disorders.
In an article in Forbes magazine, Walter Kaye, a researcher at the University of Pittsburgh studying anorexia, explains that researchers are discovering that the causes of eating disorders are physical rather than mental, “With anorexia, we’re where schizophrenia or autism were 20 years ago.” Kaye’s point is that, like eating disorders, people once blamed autism and schizophrenia on upbringing and other social factors, but now scientists know that these disorders have physical causes.
Genetic Link to Eating Disorders
In recent years, numerous scientific studies have found a genetic link to the risk of developing eating disorders. At the University of Pennsylvania department of Psychiatry, researchers conducted tests on twins and families with a history of anorexia. People who were related to one another had a higher incidence of eating disorders than people who were unrelated. Interested in this phenomenon, researchers discovered a biological link on chromosome 1 that indicated heredity plays a role in the development of eating disorders.
Kelly Klump, an associate professor of psychology at Michigan State University, conducted genetic studies on 500 female twins age 14 years. Klump found that social factors were the primary cause of eating disorders in prepubescent girls, but after a girl has her first menstrual period, genetic factors were more likely to be the primary cause. These findings complemented Klump’s earlier research which showed that girls age 11 had no genetic influences on their eating disorders, while girls age 17 exhibited hereditary disordered eating patterns. Puberty, therefore, had a dramatic impact on the girls’ susceptibility.
In another case, researchers at the Maudsley Hospital in London focused on the neurotransmitter serotonin, which regulates appetite and may contribute to anxiety. Researchers who studied the 5HT2A receptor in patients with anorexia found variations in the gene for serotonin. Women with eating disorders were twice as likely to have the variant gene than women who did not suffer from an eating disorder. The finding suggests that an increase in serotonin levels can contribute to a person’s susceptibility of acquiring anorexia.
Dr. Cynthia M. Bulik, who has led a major study on the genetic link to eating disorders, says that heredity can contribute as much as 56 percent to susceptibility, with social and environmental factors as the remaining causes.
According to the National Alliance on Mental Illness, anorexia sufferers tend to have higher than normal levels of the brain hormone cortisol, which reacts to stress, and vasopressin, a chemical in people with obsessive-compulsive disorder.
Genetic Link with Obesity?
While a genetic link has been found that can explain anorexia, the debate goes on as to whether binge eating and obesity also have genetic causes.
Genetics and biochemical imbalances can partially explain binge eating. Obesity is hereditary, as the condition is clearly found among people who are related to one another. Metabolism and the ability to break down food and generate energy varies widely in people. Moreover, a problem in the hypothalamus region of the brain, which controls hunger signals, can lead to binge eating or other eating disorders.
Hormonal mechanisms that control hunger, such as leptin and ghrelin, also can affect obesity. For example, leptin-deficient and leptin-resistant people can suffer from binge-eating. Some rare genetic abnormalities, such as Prader-Willi syndrome, predispose some people to obesity.
As scientists learn more about the human genome and its relationship to disease, no doubt other discoveries that relate mental illness to physical causes will develop. This relationship is certainly changing the way eating disorders are diagnosed and treated.