Sept. 6, 2005 -- There is increasing evidence that chemical abnormalities within the brain make some women more vulnerable to eating disorders and anxiety disorders.
Two months ago, researchers from the University of Pittsburgh reported that Dopamine is a chemical involved in weight, feeding behaviors, reinforcement, and reward. Now they are reporting that women who have recovered from eating disorders show abnormal levels of serotonin.
Both chemicals are closely tied to appetite, mood, and impulse control, which are all altered in people with eating disorders such as anorexia and bulimia.
"Both of these [chemicals] are very important modulators of how people respond to stimuli," says longtime anorexia researcher Walter H. Kaye, MD. "It makes sense that we would find disturbances in both of them."
Serotonin, Anxiety Link
In their newly published study, Kaye, researcher Ursula F. Bailer, MD, and colleagues from the University of Pittsburgh School of Medicine compared the brain activity of serotonin in women who had recovered from one of two types of anorexia -- restricting-type anorexia, characterized by severely restricting food intake alone, and bulimia-type anorexia, characterized by restrictive eating coupled with episodes of bingeing and purging.
Included in the study were 13 women who had recovered from restricting-type anorexia and 12 who had recovered from bulimia-type anorexia at least a year earlier. Eighteen healthy women with no history of eating disorders were also evaluated.
The researchers show that women who have certain types of anorexia have alterations in serotonin even one year or more after recovery.
Using brain scans, the researchers reported increased activity in a specific serotonin receptor among women recovered from bulimia-type anorexia.
In women recovering from restrictive-type anorexia, receptor overactivity was strongly associated with a type of anxiety called harm avoidance.
The study is published in the September issue of the journal Archives of General Psychiatry.
"We have known for a long time that people with eating disorders tend to be very harm-avoidant, which is not necessarily a bad thing," Kaye says. "These people tend to be very careful and precise, and they pay close attention to detail, which can be a plus in many professions. In fact, people who recover from eating disorders tend to do very well in life."
Genes and Environment
McGill University psychiatry professor Howard Steiger, PhD, has also studied serotonin levels in women with eating disorders, although his research has focused primarily on those with bulimia.
Steiger tells WebMD that the evidence strongly suggests that both genetic susceptibility and external factors like early-life abuse or trauma can trigger eating disorders.
"Our work reinforces the idea that there are different pathways that can lead to the same problems," he says. "Some people may be intrinsically susceptible to eating disorders because of heredity. Others may be constitutionally less susceptible but develop eating disorders anyway for other reasons."
The director of the Eating Disorders Clinic at Montreal's Douglas Hospital, Steiger says a better understanding of the biologic and social triggers of eating disorders offers the promise of improved treatments.
Though some anorexic patients respond well to widely used treatments, including behavioral therapy and selective serotonin reuptake inhibitors (SSRIs) such as Paxil and Zoloft, others do not.
Hayes' research team plans to study eating disorders within particularly vulnerable families in an effort to better understand genetic susceptibility. The study is supported by the National Institutes of Health and will involve approximately 400 families with two or more members with eating disorders.
"Many people do seem to have a kind of hereditary susceptibility, but that doesn't mean that they will develop an eating disorder," Steiger says. "But it may be that women who inherit this vulnerability have to be especially careful about dieting, [which can trigger eating disorders]."