Consistent with our previous findings13, markedly increased BDNF levels in colonic mucosa were confirmed (primarily in epithelial cells and interstitial tissue) in a different population of patients with IBS (Fig. 1A,B; Supplementary Fig. S1A), but there was no difference between IBS-C and IBS-D patients (data not shown). Here, BDNF is linked to irritable bowel syndrome.