An inability to stop what you are doing or are about to do can cause considerable distress. Until recently, uncontrolled eating or binge eating, an eating disorder, has been linked to reduced self-regulation under stress, or deficits in brain regions responsible for inhibitory control. But this popular theory of impulsivity-induced binge eating has no direct evidence.
A new study led by scientists at the University of Cambridge examined how experimentally induced stress affects self-regulation in normal individuals and women with anorexia and bulimia. Functional magnetic resonance imaging (FMRI) neuroimaging of participants under stressful and neutral conditions showed that stress-induced lack of self-control is too simplistic and inadequate in explaining the cause of binge eating.
These findings were reported in the article, “Prefrontal Responses During Proactive and Reactive Inhibition Are Differentially Impacted by Stress in Anorexia and Bulimia Nervosa,” published in the Journal of Neuroscience.
Earlier neuroimaging studies in patients with bulimia nervosa (BN) reported reduced activity in frontostriatal regions that are important in self-control, resulting in the popular theory that posits binge eating results from a failure of self-regulation under stress. However, there has been no direct evidence that stress impairs self-regulation in binge-eating disorders.
The researchers determined the effect of acute stress on self-control in 85 women, including 33 women with BN, 22 women with anorexia nervosa and bingeing or purging (AN-BP), and 30 normal women.
The authors performed a validated method of measuring proactive (anticipation of stopping) and reactive (outright stopping) inhibition called the stop-signal anticipation task, on all participants coupled with repeated FMRI scans for two consecutive days. The stop-signal anticipation task entailed pushing a button to stop a moving bar when it reached a specific point on the screen. On some trials, the bar stopped early, and the participants had to stop themselves from pushing the button.
The results showed women with BN showed reduced proactive inhibition while prefrontal responses were increased in women with both AN-BP and BN, whereas reactive inhibition remained intact in both diagnostic groups. Both AN-BP and BN groups showed distinct, stress-induced changes in inferior and superior frontal activity during both proactive and reactive inhibition tasks, but task performance was unaffected by stress.
These findings provide novel evidence of reduced proactive inhibition in BN, yet these inhibitory control deficits did not generalize to women with AN-BP. The results show that stress alters brain activity associated with inhibitory control in both groups of women with eating disorders but had no effect on their ability to stop their actions. These results demonstrate that self-inhibition is intact in the face of stress and the underlying neural mechanism behind binge eating is more complex than previously thought.
“Our findings identify intriguing alterations of stress responses and inhibitory function associated with binge eating, but they counsel against stress-induced failures of inhibitory control as a comprehensive explanation for loss-of-control eating,” the authors noted.