Bifidobacterium species, a group of probiotic bacteria commonly found in the human gut, have been investigated for their potential role in supporting mental health, including anxiety disorders. The rationale stems from the concept of the gut-brain axis, which describes bidirectional communication between the gastrointestinal tract and the central nervous system. Some preclinical and clinical studies suggest that specific strains of Bifidobacterium may positively influence mood and anxiety by modulating gut microbiota, reducing systemic inflammation, or influencing neuroactive substance production (such as GABA).

Human studies are limited in number and often small in scale. For example, a double-blind, placebo-controlled trial (Allen et al., 2016) found that a combination of Bifidobacterium longum and other probiotics reduced self-reported psychological distress in healthy volunteers. Another randomized controlled trial (Messaoudi et al., 2011) using B. longum and L. helveticus showed reduced anxiety scores in healthy individuals. However, direct evidence for efficacy in clinically diagnosed anxiety disorders is modest and not yet conclusive. Most studies use healthy participants, and there is variability in strains and dosages.

In summary, the use of Bifidobacterium for anxiety is grounded in early scientific research with some promising but preliminary findings. There is not yet strong, consistent clinical evidence for its use in treating diagnosed anxiety disorders, and further large-scale, well-controlled studies are needed to establish efficacy.