Molecular Imaging News
September 9, 2005
PET Depicts Alterations in Brain Serotonin Activity That May Be Associated with Anorexia Nervosa
Women recovering from bulimia-type anorexia nervosa demonstrate via PET scans an alteration in serotonin binding that is widely associated with anxiety and other affective disorders more than one year after recovery, according to a study in the September issue of Archives of General Psychiatry.
Anorexia nervosa, a disorder characterized by the relentless pursuit of thinness and obsessive fear of being fat, has two subtypes, a group that restricts their eating (restricting-type AN) and a group that alternates restrictive eating with bulimic symptoms such as episodes of purging and/or binge eating (bulimia-type AN), according to background information in the article. Previous evidence has suggested that alterations in the activity of serotonin (a brain chemical involved in communication between nerve cells) may contribute to the appetite alteration in anorexia nervosa as well as playing a role in anxious, obsessional behaviors and extremes of impulse control.
Ursula F. Bailer, MD, of the University of Pittsburgh School of Medicine (Pittsburgh) and colleagues compared the activity of serotonin in women who had recovered from each of the two types of anorexia nervosa and a control group of healthy women using positron emission tomography (PET). The researchers injected a molecule that can bind to a serotonin receptor in much the same way that serotonin does to specific areas of the women's brains and used PET scans to measure the extent of the molecule-receptor binding. This molecule-receptor binding served as a marker for alterations of serotonin neuronal activity. Thirteen women recovered from restricting-type AN, 12 women with bulimia-type AN and 18 healthy control women were included in the study.
The researchers report increased binding of this marker molecule in several brain regions in women who had recovered from bulimia-type AN but not restricting-type AN. However, the women who had recovered from restricting-type AN showed receptor binding in a brain region that correlates with a measure of anxiety called harm avoidance.
"In summary, this study lends further credibility to the possibility that women with AN have a persistent disturbance of 5-HT [serotonin] neuronal systems that may be related to increased anxiety," the authors conclude. "While it cannot be certain whether 5-HT alterations are a 'scar' following cessation of low weight and malnutrition, the fact that premorbid anxiety disorders occur in AN supports the possibility that altered 5-HT pathway function could predate the onset of AN and persist after recovery. There are no proven treatments for AN, and this illness has the highest mortality of any psychiatric disorder. These data offer the promise of a new understanding of the pathogenesis of AN and new drug and psychological treatment targets."