2. Individual IBS symptoms: The individual IBS symptom (pain/discomfort, bloating, constipation, and diarrhea) as perceived by patients will be scored in a 5-point scale (0=none or asymptomatic; 1=mild with no limitation of normal activities; 2=moderate with limitation of some normal activities; 3=intense and unable to carry out most normal activities; 4=incapacitating symptom that are intolerable and unable to carry out all normal activities).