The largest neuroimaging study of bulimia nervosa (BN) to date has found reproducible structural brain differences in women with the disorder, shedding new light on its poorly understood neurobiology. Researchers from the ENIGMA Eating Disorders Working Group analyzed MRI scans from 786 women across 17 international cohorts and found that those with BN had lower nucleus accumbens volume and reduced cortical surface area — particularly in regions tied to sensory and social processing — compared to healthy controls.

Crucially, more frequent binge eating was associated with smaller surface area across additional brain regions involved in cognitive control, reward valuation, and emotional regulation. Notably, compensatory behavior frequency — the metric currently used to define BN severity — showed no significant association with brain structure, suggesting binge eating may be the more neurobiologically meaningful symptom dimension.

By the Numbers:

• 786 women analyzed (369 with BN, 417 healthy controls) across 17 cohorts at 13 international sites
• Mean illness duration in the BN group: ~7 years
• BN participants reported a mean of ~71 binge-eating and ~116 compensatory behavior episodes in the prior 3 months
• Nucleus accumbens volume and total cortical surface area were both significantly lower in BN (Cohen's d ≈ -0.20)

Why it matters: These findings point to specific brain circuits — reward, cognitive control, interoception, and social cognition — as key players in BN's pathophysiology. For clinicians, this could eventually inform more targeted prevention and treatment strategies for an eating disorder that has long lacked a clear neurobiological framework.