Victims of bulimia could be eating abnormally due to a problem in their brain circuits, according to researchers from Columbia University and New York State Psychiatric Institute.
Bulimia nervosa often begins in the adolescent or young adult years, "primarily affecting girls and women, it is characterized by recurrent episodes of binge eating followed by self-induced vomiting or another compensatory behaviour to avoid weight gain."
The research team led by Rachel Marsh showed that disruptions in certain pathways between nerve cells known as frontostriatal circuits, responsible for controlling their behaviours, lead to severe sense of loss of control, leading to binge eating.
During the study the researchers compared the performance on the task of 20 women with bulimia nervosa with that of 20 healthy women who served as controls.
In the Simon Spatial Incompatibility task, the participants were asked to indicate the direction an arrow is pointing regardless of where it appears on a screen.
The task is easier when the arrow direction matches the side of the screen, but more difficult when, for instance, an arrow that points leftward appears on the right side of the screen. Ignoring the side of the screen to focus on the arrow direction requires regulating behaviour by fighting the tendency to respond automatically and resolving conflicting messages.
"Patients with bulimia nervosa exhibited greater impulsivity than did control participants, responding faster and making more errors on conflict trials [where the arrow direction and location did not match] that required self-regulatory control to respond correctly," wrote the authors.
"They responded faster on congruent trials following incorrect conflict trials, suggesting impulsive responding even immediately after having committed an error," they added.
When patients with bulimia did respond correctly on trials in which the arrow side and direction did not match, their frontostriatal circuits did not activate to the same degree as did those of women in the control group.
"We speculate that this inability to engage frontostriatal systems also contributes to their inability to regulate binge-type eating and other impulsive behaviours," the authors added.
The study appears in Archives of General Psychiatry, one of the JAMA/Archives journals.