While it is still unclear if dysbiosis causes or results from AN pathophysiology, new evidence from mouse studies has indicated potential causality between microbiome changes and traits of anorexia nervosa. Germ-free mice transplanted with anorexia nervosa patient microbiota (gAN) gained less weight and had poorer food efficiency compared to mice transplanted with healthy control microbiota (gHC). gAN were found to have more Clostridium and Bifidobacterium genera compared to gHC. congruent with abnormalities found in human patients. gAN were also found to display more anxious and compulsive behaviors, inversely associated with Bacteroides fecal abundance and brainstem 5-HT levels, which were lower in gAN than in age-matched gHC. However, this compulsivity was treatable with probiotic treatment of B. vulgatus, as patients often have decreased abundance of the Bacteroides fragilis group.