 Fecal Sample Collection Patients and healthy controls will collect fecal samples at home using our well-established protocol. During the recruitment visit, the subjects will be provided a kit containing a single 50-ml sterile vial with an air-tight sachet, Oxoid Anearobic kit and a cooling pad. The patients will be instructed to transfer several grams of the feces into the vial with the lid not completely tight, place the vial into the airtight sachet, tear the Oxoid sachet, place it into the airtight sachet and seal it. This will enable us to better preserve anaerobic bacteria. The samples will be transported on the cooling pad, previously placed in the freezer. To transfer the stool sample to the MacAnxiety Research Centre, the subjects will contact the study personnel and a local taxi company, which will deliver the stool sample to the clinic within four hours of defecation. The stool sample will be processed in an anaerobic chamber. Part of the stool sample will be transferred into two 5 ml cryovials and mixed with corresponding amount of Ringer-cysteine solution with 10 glycerol and then stored in -80oC freezer. The other part of the sample will be transferred into two, 2-ml cryovials and snap frozen using liquid nitrogen for molecular analysis of microbiota. 