SLC6A4 and irritable bowel syndrome: Our previous studies which focused on post‐infectious IBS (PI‐IBS), two‐thirds of whom have IBS‐D, had shown an increased number of 5‐HT containing enteroendocrine cells.5 We also showed in animal models of PI‐IBS6 that colonic mucosal 5‐HT was elevated immediately after infection and 5‐hydroxyindole acetic acid (5‐HIAA)/5‐HT ratios were increased while, serotonin transporter gene (SERT gene SLC6A4) mRNA expression was depressed up to 56 days post‐infection, these two changes  suggesting long‐lasting accelerated mucosal 5‐HT turnover.