The therapeutic effects of <i>Lacticaseibacillus rhamnosus</i> on stress-induced anxiety: a systematic review of evidence from animal studies

<i>Lacticaseibacillus rhamnosus</i> may modulate stress-induced anxiety, yet animal evidence has not been systematically evaluated. Following PRISMA guidelines, PubMed, Embase, and Scopus were searched (2011-2024) for animal studies evaluating the role of <i>L. rhamnosus</i> in stress-induced anxiety. Primary outcomes were behavioural anxiety measures; secondary outcomes included neuroendocrine, immune, epithelial, and microbiota changes. Fifteen studies met the inclusion criteria. Species included mice (n=7), rats (n=5), and hens (n=3). Stress models comprised chronic unpredictable mild stress (n=8), social defeat (n=2), maternal separation (n=1), restraint stress (n=1), and severe feather-pecking (n=3). Common strains were JB-1 (n=8), HN001 (n=2), LGG (n=2), LR-32 (n=1), 4B15 (n=1), and LR3201 (n=1). Of the 15 studies, 12 reported significant anxiolytic effects, most frequently in the elevated plus maze (7/10) and open-field test (6/9). JB-1 showed the most consistent behavioural improvement (7/8 studies). Mechanistic findings were reported in subsets of studies: HPA axis modulation in 4/15, monoamine changes in 4/15, GABAergic effects in 4/15, immune/anti-inflammatory changes in 4/15, tight junction restoration in 2/15, and gut microbiota or SCFA-related changes in 7/15. <i>L. rhamnosus</i>, particularly strain JB-1, shows consistent anxiolytic effects and multiple putative mechanistic pathways, though more rigorous and standardised preclinical designs are needed.