Understanding the neurocognitive effects of fecal microbiota transplantation in major depressive disorder patients with and without irritable bowel syndrome

This study is a phase 2/3 open-label controlled trial (CT) in which adults with Major Depressive Disorder (MDD) and adults who have MDD plus comorbid Inflammatory Bowel Syndrome (IBS) will be assigned to either receive oral Fecal Microbiota Transplantation (FMT) or to continue with the treatment they are currently receiving in a Treatment As Usual (TAU) arm. An IBS alone group receiving TAU will be recruited as a clinical control group. The primary goals of this study are to determine effectiveness, safety and tolerability of oral FMT in adults with MDD and in MDD who have comorbid IBS. Additional goals are to characterize patterns and progressions of cognitive and neural correlates associated with MDD and with MDD + IBS and to determine if they improve with FMT. It is known that both, individuals with MDD and those with MDD and IBS show cognitive alterations as well as changes in neural structures, but this study is designed to see if those are changed with treatment response to FMT. Additionally, trial feasibility will be monitored via recruitment rate, study visits adherence and participant retention to inform future trial scalability."