Serotonin Function in Bulimia Nervosa

Dieting and binge eating may promote secondary decreases in brain activity of serotonin (5-hydroxytryptamine, or 5-HT), and might explain the reduced 5-HT tone found in patients with bulimia nervosa. Along the same lines, bulimia nervosa patients have been shown to have some changes in brain activity of serotonin from binge-eating and purging. These changes included blunted neuroendocrine responses to 5-HT precursors and agonists, and reduced platelet binding of 5-HT uptake inhibitorsall signs of impaired 5-HT neurotransmission.

Howard Steiger, PhD, and colleagues at McGill University and the University of Montreal, recently identified two subtypes of women with bulimic disorders, based on high and low levels of serotonin (J Clin Psychiatry 2004;65:830). The 5-year controlled study (conducted from 1999 to 2003) included 73 women with bulimic disorders recruited through a specialized eating disorders program for adults and 50 normal healthy women without eating disorders who were recruited through newspaper ads. The bulimic women had body mass indexes (BMIs) under 30, binge-ate at least once a week, and were not pregnant, anorexic, or on psychoactive medication. The 50 healthy control women were from 18 to 40 years of age, and had BMIs between 18 and 30.

Measures of paroxetine-binding density and affinity led to classification of the bulimic women into groups with “low density/low affinity” (52) or “high density/low affinity” (21) paroxetine binding. When Dr. Steiger and colleagues examined paroxetine-binding scores, they assigned low transporter density and high transporter densities.

Patients with low transporter density had a greater propensity of childhood sexual abuse and, as a trend, borderline personality disorder. These findings were compatible with findings that link reduced 5-HT activity in bulimia nervosa sufferers to greater impulsivity, borderline traits, self-mutilation and hostility and (in bulimic and nonbulimic women alike) exposure to childhood abuse. Compared with the control women, the bulimic women had significantly higher Eating Attitudes Test-26 (EAT-26), Center for Epidemiologic Studies Depression (CESD) scale, and impulsivity, compulsivity, and perfectionism scores.

His group also found a subgroup of women with high 5-HT density scores, characterized by a proneness to perfectionism, compulsivity, and relatively low risk of childhood sexual abuse. The findings in this group also challenged the prevailing belief that binge eating arises from a generalized reduction in levels of 5-HT.

According to the authors, these findings are among the first to demonstrate a convergence of trait-related developmental, and serotonergic factors that could underlie the different clusters of bulimic persons. Further, they state that their findings suggest that “traits” are an important organizing construct in modeling eating and related pathologies.