Abstract： To the Editor:Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder that presents as abdominal pain with altered bowel habits.The patho-physiologic mechanism of IBS is not well understood,although many hypotheses have been proposed,including visceral hypersensitivity,gastrointestinal dysmotility,low-grade inflammation of the intestinal mucosa,and dysfunction of the brain-gut interaction.Dysfunction of the braingut interaction is thought to be involved in IBS because a considerable proportion of patients with IBS have some form of psychologic comorbidity,such as depression or anxiety.In addition,mental and psychologic problems increase the risk for IBS and the symptom severity of IBS.Recently,changes in the gut microbiota have also been suggested to contribute to both IBS and depression.Our previous study demonstrated significant altered gut microbiota profiles in patients with diarrhea-predominant IBS (IBS-D) and depression.[1]