Bifidobacteria, a genus of probiotic bacteria, have been investigated in the context of the gut-brain axis and their potential role in modulating anxiety symptoms. Several preclinical studies in animals and a limited number of small-scale human clinical trials suggest that certain strains of Bifidobacteria may help reduce symptoms of anxiety, possibly by influencing neurochemical pathways, reducing inflammation, and improving gut health. For example, Bifidobacterium longum 1714 and Bifidobacterium longum NCC3001 have shown anxiolytic effects in animal models and in some human studies, including reduced stress responses and improved self-reported well-being.

However, the evidence base remains limited. Most human studies have small sample sizes, short durations, and often combine Bifidobacteria with other probiotic strains, making it difficult to attribute effects specifically to Bifidobacteria. Systematic reviews and meta-analyses suggest a modest benefit for probiotics (including Bifidobacteria) on anxiety symptoms, but results are inconsistent and often of low quality. There is no robust evidence to recommend unspecified Bifidobacteria for treating clinically diagnosed anxiety disorders in place of established therapies. Further large, well-controlled clinical trials are needed to clarify the efficacy, optimal strains, and mechanisms involved.