"In a 2018 article published in the journal Bipolar Disorders, researcher Faith Dickerson and colleagues reported that in a small study of 66 people who had been hospitalized for mania, taking specific probiotic supplements upon their release reduced re-hospitalizations compared to taking placebo.
The study followed patients for 24 weeks after their hospitalization. They were randomized to receive either the combination of Lactobacillus rhamnosus strain GG and Bifidobacterium animalis subsp. lactis strain Bb12 or placebo in addition to their regular medications. While 17 of the 33 participants in the placebo group (51.5%) had at least one re-hospitalization during the study period, only eight (24.2%) of the participants taking probiotics had a re-hospitalization. The duration of the re-hospitalizations was also shorter for those taking probiotics (2.8 days on average versus 8.3 days for those taking placebo).
In a personal communication to this editor (Robert M. Post), Chris Aiken, Instructor in Clinical Psychiatry at Wake Forest University School of Medicine, who was not involved in the study, provided some clarifying details to this editor about the use of probiotics to reduce manic relapse. Aiken explained, “Apparently, it’s important to get both the right species (e.g. Bifidobacterium lactis) and the right strain (e.g. Bb-12) in choosing a probiotic. The study mentions that one of the strains (Bb-12) is patented and only available in Europe, but it has been licensed to a few U.S. companies."