Irritable bowel syndrome (IBS) is a chronic disorder of gut-brain interaction marked by recurring abdominal pain and changes in bowel habits. It occurs without identifiable structural damage that explains the symptoms.
In a 2010 Harvard study, IBS patients handed pills labelled "Placebo — inert ingredients" still improved significantly more than untreated patients. The brain responds to the ritual of swallowing a pill even without deception — triggering real neurochemical changes.