International Psychometric Validation Study of the Intestinal Gas Questionnaire (IGQ)

Inclusion Criteria: All (subjects with IBS diagnosis and general population): * Complaining of gas-related symptoms (GRS) of a certain severity level: subjects with IBS diagnosis and general population need to report a score of 4 or greater on at least one symptom on the symptom screening tool * Cognitive and linguistic capability to complete several self-questionnaires * BMI \> 18.5 and \< 30.0 kg/m2 * Agreement of the subject to participate in the study Subjects with IBS diagnosis: * IBS diagnosis using Rome III diagnostic criteria for Functional Gastrointestinal Disorders (21) * IBS severity: IBS-SSS score of 75 to 300 General population: * Subjects not fulfilling IBS Rome III criteria * Regular stool frequency (i.e., between 3 and 21 bowel movements per week) Exclusion criteria All (subjects with IBS diagnosis and general population): * Recent (2 last weeks) change in diet or intake of potentially flatulogenic compounds (fiber, lactulose) * Organic gastrointestinal disease * Other functional gastrointestinal disorder as defined by Rome III criteria * Any severe and progressive disease (e.g. depression, cancer, uncontrolled diabetes, rheumatoid arthritis…) * Any severe psychiatric disorder (e.g. acute episode of schizophrenia or bipolar disorder…) * Pregnant women * Being under the direct hierarchy of the investigatorBelonging to the site's staff team General population: * Treatment for diarrhea or constipation including lactulose