The Safety, Efficacy, and Feasibility of Fecal Microbiota Transplantation in a Population With Bipolar Disorder During Depressive Episodes: A Pilot Parallel Arm Randomized Controlled Trial: Sécurité, efficacité et faisabilité de la transplantation de microbiote fécal chez une population atteinte de troubles bipolaires, au cours d'épisodes dépressifs : essai pilote contrôlé à répartition aléatoire et à groupes parallèles.
Shahrokh Shekarriz, Simone N Vigod, Teresa Bianco et al.
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In 30 seconds
This double-blind, parallel-arm pilot randomised controlled trial assessed fecal microbiota transplantation (FMT) alongside approved therapy in 35 people with at least moderate depressive-phase bipolar disorder who had not responded to standard treatment. Participants received donor-derived (allogenic) or their own stool (autologous) FMT and were followed for 24 weeks. Depression scores improved in both groups, but the between-group difference was not significant: MADRS improved by 16.74 points with allogenic FMT and 15.4 points with autologous FMT (p = .64). Donor FMT altered microbial profiles and increased diversity; the intervention was well tolerated.
Key findings
- MADRS improved by 16.74 points with allogenic FMT and 15.4 points with autologous FMT; the between-group difference was not significant (p-value = .64).
- Allogenic FMT produced a bacterial profile resembling the healthy donor and increased bacterial diversity at the 6-month mark; autologous FMT did not.
- The intervention was well tolerated, with no significant adverse events reported.
Why it matters
The trial provides early evidence that FMT can be delivered and was tolerated in people with bipolar depression, while also demonstrating measurable microbiome changes after donor FMT. However, improvement in depression was similar with donor and autologous stool, so the findings do not establish a specific antidepressant effect of donor microbiota. They help define questions for larger, appropriately controlled studies.
What to keep in mind
This was a small pilot trial with 35 participants and no true placebo arm; the comparison of donor with autologous FMT cannot establish whether either intervention improves depression beyond other effects of study participation or treatment.