# The therapeutic effects of Lacticaseibacillus rhamnosus on stress-induced anxiety: a systematic review of evidence from animal studies

## TL;DR

This review finds that Lacticaseibacillus rhamnosus, especially strain JB-1, consistently reduces stress-induced anxiety in animal studies.

## Contribution

The paper provides the first systematic review of animal evidence on L. rhamnosus for stress-induced anxiety.

## Key findings

- 12 out of 15 studies reported significant anxiolytic effects of L. rhamnosus.
- Strain JB-1 showed the most consistent behavioral improvement across studies.
- Multiple mechanisms, such as HPA axis and gut microbiota changes, were associated with its effects.

## Abstract

Lacticaseibacillus rhamnosus 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 L. rhamnosus 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. L. rhamnosus, particularly strain JB-1, shows consistent anxiolytic effects and multiple putative mechanistic pathways, though more rigorous and standardised preclinical designs are needed.