Immunomodulatory Effects of Probiotic Supplementation in Schizophrenia Patients: A Randomized, Placebo-Controlled Trial

Although peripheral immune system abnormalities have been linked to schizophrenia pathophysiology, standard antipsychotic drugs show limited immunological effects. Thus, more effective treatment approaches are required. Probiotics are microorganisms that modulate the immune response of the host and, therefore, may be beneficial to schizophrenia patients. The aim of this study was to examine the possible immunomodulatory effects of probiotic supplementation in chronic schizophrenia patients. The concentrations of 47 immune-related serum proteins were measured using multiplexed immunoassays in samples collected from patients before and after 14 weeks of adjuvant treatment with probiotics (Lactobacillus rhamnosus strain GG and Bifidobacterium animalis subsp. lactis strain Bb12; n = 31) or placebo (n = 27). Probiotic add-on treatment significantly reduced levels of von Willebrand factor (vWF) and increased levels of monocyte chemotactic protein-1 (MCP-1), brain-derived neurotrophic factor (BDNF), RANTES, and macrophage inflammatory protein-1 beta (MIP-1) beta with borderline significance (P ≤ 0.08). In silico pathway analysis revealed that probiotic-induced alterations are related to regulation of immune and intestinal epithelial cells through the IL-17 family of cytokines. We hypothesize that supplementation of probiotics to schizophrenia patients may improve control of gastrointestinal leakage.