Altered fimbria-fornix white matter integrity in anorexia nervosa predicts harm avoidance

The eating disorder anorexia nervosa (AN) is associated with high anxiety. The brain mechanisms that drive those behaviors are unknown. In this study we wanted to test whether brain white matter (WM) integrity is altered in AN, and related to heightened anxiety. Sixteen adult women with AN (mean age 24 ± 7 years) and 17 healthy control women (CW, mean age 25 ± 4 years) underwent diffusion tensor imaging (DTI) of the brain. The DTI brain images were used to calculate the fractional anisotropy (FA) of WM tracts, which is a measure for WM integrity. AN individuals compared to CW showed clusters of significantly reduced FA (p<0.05, corrected) in the bilateral fimbria-fornix and the fronto-occipital fasciculus, as well as the posterior cingulum WM. In the AN group, Harm Avoidance was predicted by FA in the left and right fimbria-fornix. Those findings were not due to WM volume deficits in AN. This study indicates that WM integrity is abnormal in AN in limbic and association pathways, which could contribute to disturbed feeding, emotion processing and body perception in AN. The prediction of Harm Avoidance in AN by fimbria-fornix WM integrity suggests that this pathway may be mechanistically involved in high anxiety in AN.