IBS-C Questionnaire Study

Inclusion Criteria: Group 1 (IBS-C) * ≥18 years old * Decrease of frequency of bowel movement (\<3 time per week), change of stool consistency (stool that is hard and difficult to pass, Bristol Types 1 to 3), or other 'constipation symptoms' judged by investigators. * With abdominal symptoms such as abdominal pain, bloating, and abdominal discomfort, or other 'constipation symptoms' judged by investigators. * Result of ROME VI marked as 'IBS-C'. Group 2 (non-IBS-C) * ≥18 years old * Decrease of frequency of bowel movement (\<3 time per week), change of stool consistency (stool that is hard and difficult to pass, Bristol Types 1 to 3), or other 'constipation symptoms' judged by investigators. * With abdominal symptoms such as abdominal pain, bloating, and abdominal discomfort, or other 'constipation symptoms' judged by investigators. * Result of ROME VI marked as 'Non IBS-C'. Exclusion Criteria: * Individuals with a cognitive condition and unable to finish the questionnaire. * Individuals have an acute or chronic non-GI condition that can be associated with constipation; e.g., central nervous system cause (Parkinson's disease, spinal cord injury, and multiple sclerosis), pseudo-obstruction, colonic inertia, megacolon, megarectum, bowel obstruction, descending perineum syndrome, solitary rectal ulcer syndrome, systemic sclerosis. * Individuals who had been diagnosed with the following organic health problems likely to affect GI symptoms: * Inflammatory bowel disease (Crohn's disease or ulcerative colitis) * cancer anywhere in the GI tract or current infection of the GI tract. * Pelvic floor dysfunction. (i.e., disease that is not adequately treated or stable with therapy.) * Any history of colon surgeries. * Individuals who participate in any interventional study currently. * Not suitable for the study judged by investigators.