Probiotics Linked to Cognitive and Gut Health Benefits in Bipolar Disorder and Schizophrenia

In individuals with bipolar disorder (BD) or schizophrenia spectrum disorders (SSD), a probiotic supplement may offer cognitive and gut health improvements with minimal effects on symptom severity, according to findings published in Schizophrenia Bulletin.

Researchers conducted a double-blind, randomized, placebo-controlled trial evaluating the efficacy of probiotics as an adjunctive treatment in BD and SSD. The current trial, which spanned 12 weeks, aimed to assess changes in psychiatric symptoms, cognitive function, and gut health markers.

Participants included diagnosed with BD or SSD based on DSM-V criteria. They were randomly assigned in a 1:1 ratio to receive either the probiotic or a placebo alongside standard treatment. The probiotic consisted of 9 bacterial strains designed to improve gut barrier function and had previously documented positive effects on cognition and depressive symptoms.

Stool and blood samples were collected to evaluate markers of intestinal permeability and inflammation, while cognitive assessments were conducted using the Brief Assessment of Cognition in Schizophrenia. Other clinical measures included psychiatric symptom severity, gastrointestinal symptoms, and fatigue. 

Overall, the sample population included 131 adults, of whom 67 received probiotics and 64 received a placebo. Among the treatment group, 58.2% were women; 40.3% had an SSD diagnosis; and the mean age was 43.

The primary outcomes were changes in psychiatric symptoms and cognition. Although no significant differences were observed in overall psychiatric symptom severity, verbal memory showed significant improvement in the probiotic group compared with placebo (Linear Mixed Model [LMM] effect size. 0.33; 95% CI, 0.04-0.61, P=.027). However, after adjusting for multiple testing, this significance become borderline. (adjusted P=.059).

Secondary outcomes highlighted significant improvements in gut health markers. In the probiotic group, serum zonulin showed a substantial decrease (LMM, −18.40; adjusted P=.002). Similarly, reductions were observed in fecal zonulin (LMM, −10.47; adjusted P=.014) and alpha-1 antitrypsin levels (LMM, -9.26; P=.025). Male participants experienced significant reductions in indigestion symptoms compared with those receiving placebo (LMM, −0.70; adjusted P=.010).

No significant changes were observed in overall psychiatric symptom severity between groups. Exploratory analysis revealed sex-specific trends, such as enhanced processing speed in men (LMM, 0.37; adjusted P =.059) and improved problem-solving in women (LMM, 0.45; adjusted P =.059), though these did not survive correction for multiple comparisons.

Safety profiles were comparable between groups, with adverse events reported in 17.5% of placebo and 10.3% of probiotic participants.

“Given the high tolerability and acceptability of probiotic formulations, these findings underscore the potential for further research into the gut–brain axis and probiotic therapy as a promising augmentation strategy for SSD and BD patients,” the researchers concluded.

Study limitations include recruitment challenges during the COVID-19 pandemic, high baseline dietary quality among participants, and limited representation of individuals with severe symptoms.

This article originally appeared on Psychiatry Advisor