Which Probiotics Have Been Studied For Their Effects On Anxiety And Depression Symptoms In Humans?

What the research shows

Multiple high-quality randomized controlled trials and meta-analyses indicate that probiotics can reduce symptoms of depression and anxiety. Meta-analyses (PMID: 39731509, 34620373, 41310510, 40440772) show significant reductions in depression and anxiety scores with probiotic supplementation, though heterogeneity exists. Specific strains with evidence include Lactiplantibacillus plantarum (PMID: 40312029, 40008414), Lactobacillus rhamnosus HN001 (PMID: 28943228), Bifidobacterium longum NCC3001 (PMID: 28483500), and multispecies probiotics (PMID: 30991255, 40222448). Some studies report improvements in mood and anxiety in healthy adults, postpartum women, patients with irritable bowel syndrome, and cancer patients undergoing chemotherapy. Mechanisms involve modulation of neurotransmitters (GABA, serotonin), immune regulation, and gut-brain axis signaling. Evidence for prebiotics is less consistent. Safety profiles are generally favorable with no serious adverse events reported. Limitations include variability in strains, doses, populations, and study durations, as well as some inconsistent findings and need for long-term data.

Best studied probiotic strains

Who may benefit

Safety

Probiotic supplementation is generally safe with no serious adverse events reported in the reviewed studies. Some studies specifically noted no adverse effects over intervention periods ranging from weeks to months. However, long-term safety data are limited and should be further investigated.

Limitations

There is considerable heterogeneity in probiotic strains, doses, treatment durations, and populations studied, which limits direct comparisons and generalizability. Some studies show inconsistent or modest effects, and the mechanisms of action are not fully elucidated. Evidence for prebiotics and synbiotics is less robust. Many studies have small sample sizes or short follow-up periods. More large-scale, well-designed RCTs with standardized protocols and long-term follow-up are needed to confirm efficacy and safety and to identify optimal strains and treatment regimens.

PubMed sources