Lactobacillus rhamnosus (often referenced as Lactobacillus, but now more correctly as Lacticaseibacillus rhamnosus) has been investigated for its potential effects on mental health, especially anxiety, as part of the emerging field of “psychobiotics.” Several animal studies, particularly the widely cited Bravo et al. (2011) study, have shown that L. rhamnosus supplementation can modulate GABA receptor expression and reduce anxiety- and depression-related behaviors in mice, possibly via the vagus nerve. These findings have generated interest in the probiotic’s potential to impact the gut-brain axis.

However, clinical evidence in humans is limited and mixed. A few small randomized controlled trials have explored the effects of L. rhamnosus on psychological outcomes in humans, but results are not consistent or robust. For example, a 2016 trial in healthy volunteers found no significant effect on mood or anxiety, while other studies suggest modest improvements in stress or mood, often as part of multi-strain formulations rather than L. rhamnosus alone. Systematic reviews (e.g., Wallace & Milev, 2017; Reis et al., 2018) generally conclude that while preliminary findings are promising, the overall quality and quantity of evidence is insufficient for strong recommendations.

In summary, while there is some scientific basis for the use of L. rhamnosus to support anxiety, the evidence is limited and not definitive. More high-quality, large-scale human studies are needed.