We used IBS, serotonin, SERT, 5HT3 receptor, diarrhea, constipation, abdominal pain, 5HT3 antagonist, 5HT4 agonist, management of IBS, and antidepressant as keywords alone and in combination to look for published papers from the last five years in the English language. The gene discussed is SLC6A4; the disease is irritable bowel syndrome.