The efficacy of Lactobacillus and Bifidobacterium in patients with schizophrenia: a meta-analysis

The modulation of gut microbiota through probiotics holds promise as a novel avenue for schizophrenia treatment. This study aims to analyze probiotic complementary therapy on individuals with schizophrenia systematically, to investigate probiotic efficacy, potential mechanisms, and implications for clinical practice. Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched in Medline, Web of Science, Embase, ClinicalTrials.gov, CNKI, VIP, and WanFang databases using keywords ("probiotics" OR "prebiotics" OR "synbiotics" OR "Lactobacillus" OR "Bifidobacterium") AND ("schizophrenia"), focused on randomized controlled trials published before July 1, 2023. Among the identified studies, 8 randomized controlled trials met the inclusion criteria, encompassing a total of 342 participants in the intervention group and 306 participants in the control group. Our analysis revealed a statistically significant reduction (p = 0.03) in the total Positive and Negative Syndrome Scale (PANSS) scores following probiotic treatment in individuals with schizophrenia. While no statistical significance was observed in individual subscales (P > 0.05), significant improvements were noted in insulin levels, Insulin Resistance Index (IRI), and glucose levels. Additionally, the Quantitative Insulin Sensitivity Check Index (QUICKI) demonstrated a significant increase (all P < 0.05). The probiotic intervention significantly reduced gastrointestinal discomfort among schizophrenia patients (P = 0.003). This study suggests that probiotics could hold therapeutic potential for addressing clinical symptoms, abnormal glucose metabolism, and gastrointestinal discomfort in individuals with schizophrenia. Future research should encompass comparative trials employing robust experimental designs to explore the differential effects of various probiotic strains on schizophrenia treatment to provide evidence-based therapeutic approaches. TRIAL REGISTRATION: This review protocol was pre-registered on PROSPERO (No. CRD42023455273).