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.

BackgroundThe gut microbiome has been proposed as a potential modifiable target to treat mental illness. This double-blind randomized control trial investigated fecal microbiota transplant (FMT) in bipolar disorder (BD) to assess efficacy, safety, and feasibility. The primary outcome evaluated the effectiveness of standard approved therapy for BD depression + FMT in individuals not responding to standard treatment, measured by change in the Montgomery-Åsberg Depression Rating Scale (MADRS) score from baseline to week 24. Secondary outcomes included FMT's impact on anxiety, global function, side-effects, and safety. The feasibility of this novel intervention was also assessed. Microbial analysis utilized whole-genome shotgun metagenomic sequencing, comparing outcomes between allogenic (donor) and autologous (participants own) FMT.MethodsA total of 35 participants (28 women and 7 men) with at least moderate depressive-phase BD (MADRS) were randomized to receive either allogenic FMT (n = 17) or autologous FMT (n = 18) via colonoscopy and were followed for 24 weeks.ResultsMADRS scores significantly improved from baseline to the last visit in both treatment arms. There was no significant difference between allogenic FMT (16.74-point improvement) and autologous FMT (15.4-point improvement) regarding clinical efficacy (t = -0.47, p-value = .64, 95% confidence interval [CI] = -7.3-4.6). Microbiota analysis showed that allogenic FMT let to a bacterial profile similar to the healthy donor and increased bacterial diversity at the 6-month mark, whereas those receiving autologous FMT did not. The intervention was well tolerated with no significant adverse events. Recruitment, randomization, and retention metrics support feasibility of a larger trial.ConclusionFeasibility and tolerability data indicate further investigation into microbial manipulation in BD is warranted. The absence of efficacy differences between the two types of FMT, despite microbial change, highlights the importance of a true placebo in future studies, as well as the importance of understanding exactly what bacteria are linked to improvements. ClinicalTrials.gov, NCT0327922.