BETHESDA, MD. -- A complex set of predisposing, precipitating, and perpetuating factors appears to play a major role in driving the behavioral and neurochemical changes of patients with anorexia or bulimia, Craig Johnson, Ph.D., said at the annual conference of the National Eating Disorders Association.
"A belief system develops, and from that belief system, behaviors emerge. When those behaviors emerge, that also starts to alter the psychology and physiology of the patient and can set up these perpetuating factors so that they feed back on the predisposing and precipitating factors," said Dr. Johnson, founder and director of the eating disorders program at the Laureate Psychiatric Clinic and Hospital in Tulsa, Okla.
The factors that serve to perpetuate an eating disorder may have little to do with why the illness is continuing. The structural and functional changes to neurochemical pathways in the brain that occurred as a result of the eating disorder behavior will continue to reinforce whatever stimulation was gained from the behavior, he said.
"Without exception, patients we're taking care of entered into these behaviors to try to fix something in themselves. It was a self-improvement strategy. They thought they were doing a good thing. They were doing the same things they saw encouraged throughout our culture," Dr. Johnson said.
As they lost weight or altered their neurochemistry, though, "they stepped on a land mine, which is going to have a strong genetic predisposition to turn something on in their brain, which then sends them cascading down that road of being obsessed with weight loss and being compelled to accomplish it," he explained.
"Eating disorders are as heritable, have the same level of relative risk, and look to be as genetically mediated as the other major psychiatric illnesses," Dr. Johnson said.
If a relative has anorexia nervosa, other members of the family are 12 times more likely to develop the disorder than members of the general population. Similarly, if one family member has bulimia nervosa, other members are four times more likely to have it.
About two-thirds of eating disorder patients have a comorbid diagnosis of anxiety or depression, which predates the onset of the eating disorder in about half of such patients, he said.
Some patients also have an impaired ability to work with different sets of challenges on neuropsychological tests, although this measure is not correlated with intelligence. These test results "make sense, in terms of what we see happening to them when they move into increasing levels of complexity developmentally, starting with puberty," he said.
Even though he and his colleagues are seeing gender, ethnic, and socioeconomic drift in the epidemiology of anorexia nervosa and bulimia, Dr. Johnson noted that they are still illnesses that primarily affect white females. Girls who drop below about 17% body fat lose the secondary sexual characteristics associated with puberty and flatten out their hormone profiles so that they don't "feel" the effects of puberty, Dr. Johnson said.
"In our treatment center, one of the things we want to know as soon as we can is where the menstrual threshold is. …