Irritable bowel syndrome

Irritable bowel syndrome is a chronic and very common disorder of gut-brain interaction, meaning the ongoing conversation between the digestive tract and the nervous system. It is recognized by two things together: abdominal pain that comes back again and again, and a change in bowel habits, that is, in the form and frequency of bowel movements.

The exact cause is not known. What have been identified are the pieces involved. One is the disruption of that gut-brain axis. Another is visceral hypersensitivity: the receptors in the gut send more signals to the central nervous system than they should. The signal traveling from the gut to the brain arrives with the volume turned up. Added to that are dysmotility, which is irregular movement of the intestine, and changes in the microbiota, the community of bacteria that live inside it.

That explains what the person feels. Gas-related bloating hurts more than one would expect, and transit shifts in opposite directions: it slows down in the constipation subtype and speeds up in the diarrhea subtype.