Lactobacillus plantarum PS128 is considered a psychobiotic—a probiotic that confers mental-health benefits via the gut–brain axis—because multiple animal and human studies show it can influence mood, stress, sleep, and neurobehavioral outcomes. The term psychobiotic itself refers to live microbes that, when taken in adequate amounts, produce benefits in psychiatric or brain-related domains through microbiota–brain signaling PubMed.

Lactobacillus plantarum PS128 supports the gut–brain axis through several complementary pathways: it modulates neurotransmitter signaling (preclinical work shows chronic PS128 raises dopamine and serotonin in brain regions tied to mood and stress) and reduces anxiety-/depression-like behaviors, indicating direct microbe-to-brain effects. PubMed+1 In humans, randomized trials report improvements in depressive symptoms and sleep alongside shifts in autonomic balance (HRV), consistent with vagal/brain–body regulation. PMC+1 Clinical studies in children with autism spectrum disorder also show behavioral improvements, suggesting PS128’s gut-brain signaling has real-world relevance beyond healthy volunteers. PMC+1 Early human data further point to lower inflammation and better gut-barrier status, mechanisms known to influence brain function via immune and metabolic crosstalk. PMC Taken together, these findings indicate PS128 can tune microbial, neural, and immune pathways that shape mood, stress response, and behavior.