In new research published in Psychological Medicine, scientists aimed to shed light on the neurobiology of anorexia nervosa (AN) and body dysmorphic disorder (BDD) and to identify any overlapping features by comparing the brain network organization of participants with each disorder.
Many similar features are identified in both AN and BDD, and the 2 disorders often co-occur: An estimated 25% to 39% of patients with AN also meet diagnostic criteria for BDD. Both disorders involve preoccupation with appearance and compulsive behaviors, for example, and the peak age of onset for each occurs during adolescence. Individuals with either disorder typically have poor insight and delusional beliefs. However, the gender distribution for AN and BDD represents one notable difference between the two: While BDD affects males and females in roughly equal numbers, approximately 90% of individuals with AN are female.
While prior research has revealed abnormal modularity patterns in the brains of patients with other mental disorders such as obsessive-compulsive disorder (OCD) and schizophrenia, the current study is the first to investigate these patterns in individuals with AN and BDD. The sample included 31 healthy controls, 29 participants with BDD, and 24 individuals who previously met DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition) criteria for AN but who were weight-restored with a body mass index of ≥18.5 kg/m2 at the time of the study. This criterion was included for the AN group to avoid confounding effects of starvation on brain activity. Participants were unmedicated, and they underwent several assessments to screen for primary and co-occurring diagnoses and certain cognitive features.
Each participant underwent diffusion-weighted magnetic resonance imaging (MRI) and graph theory was used to analyze structural connectomes in the brain. In humans, these have a modular structure: The regions of the brain form modules “such that regions in the same module are highly interconnected (but less so among regions in different modules),” the authors explained. “The balance between segregation of specialized systems (modules) and their integration is essential for efficient information processing and rapid transfer within and between these specialized systems,” they wrote. They predicted that participants with AN and BDD would have shared abnormalities compared with controls.
For AN, the findings show abnormal modularity that involved frontal, basal ganglia, and posterior cingulate nodes, which “may have implications for understanding integration between reward and habit/ritual formation, as well as conflict monitoring/error detection,” in the disorder, the authors wrote. Though similar results were observed in participants with BDD, they were not statistically significant, possibly because the study was underpowered for such a comparison, in which the differences in magnitude may be smaller for BDD vs controls.
As for future research directions, the authors note that BDD and AN share similar features with OCD and state that “a similar study design that additionally includes an OCD group… will allow for more direct comparison of neural circuitry implicated in this study.”
Zhang A, Leow A, Zhan L, et al. Brain connectome modularity in weight-restored anorexia nervosa and body dysmorphic disorder. Psychol Med. 2016; doi:10.1017/S0033291716001458.