In patients with functional dyspepsia, altered alpha-adrenoreceptor function and depression are prevalent, features that are linked to a G-protein beta 3 (GNB3) subunit gene polymorphism (C825T).
Only the group of patients with diarrhea-predominant irritable bowel syndrome showed a significant correlation between the TPH1 rs211105 T/T genotype and lower scores for role physical and mental health, and higher scores for indigestion and diarrhea.