Scientists have produced evidence that the eating disorder anorexia nervosa is linked to disrupted brain chemistry.
They have shown a form of the disorder is associated with an alteration of the activity of serotonin - a chemical linked to mood and anxiety.
The University of Pittsburgh team hope their work could lead to the development of new drugs and psychological treatments.
The study is published in Archives of General Psychiatry.
The main symptom of anorexia nervosa is the relentless pursuit of thinness through self-starvation, driven by an obsessive fear of being fat.
There are two sub-types. One simply involves restricting food intake, the other involves periods of restrictive eating alternated with episodes of binge eating and /or purging, rather like bulimia.
The Pittsburgh team compared serotonin activity in women who had recovered from both sub-types of the disorder, with that in women who had never developed an eating disorder.
Using sophisticated brain scans, they showed significantly higher serotonin activity in several parts of the brains of women who had recovered from the bulimia-type form of the disorder.
Serotonin levels were also heightened in the group who had recovered from restricting-type anorexia, but not significantly so.
However, the highest levels in this group were found among those women who showed most signs of anxiety.
The researchers say their work suggests that persistent disruption of serotonin levels may lead to increased anxiety, which may trigger anorexia.
However, they could not rule out the possibility that serotonin levels were altered by the malnutrition associated with the disorder.
The researchers, led by Dr Ursula Bailer, said: "There are no proven treatments for anorexia nervosa, and this illness has the highest mortality of any psychiatric disorder.
"These data offer the promise of a new understanding of the pathogenesis of anorexia nervosa and new drug and psychological treatment targets."
Professor Janet Treasure, an expert in eating disorders at King's College London said other research had suggested eating disorders were linked to disrupted serotonin levels.
She told the BBC News website: "The addition of drugs to psychotherapy for anorexia nervosa may be of help, especially in an outpatient setting, but adherence could be a problem as people with anorexia nervosa often are worried about taking drugs."
The King's team work with the Pittsburg team in a large International study to seek answers to the questions about what can cause or cure eating disorders.
They are currently seeking families in which more than one person has an eating disorder in order to define risk factors in the genes, in development and in the environment.