Several probiotic strains and multispecies formulations have been studied for anxiety, with evidence suggesting potential benefits, though strain-specific effects and study limitations exist.
What the research shows
Multiple high-quality systematic reviews and meta-analyses indicate that probiotics may improve anxiety symptoms, though results vary by strain, population, and study design. Lactobacillus rhamnosus HN001 showed significant reductions in postpartum anxiety symptoms. Multispecies probiotic supplements demonstrated improvements in anxiety and mood in healthy older adults and working adults. Psychobiotic formulations improved anxiety in surgical oncology patients. Some studies report mixed or low-certainty evidence, and many do not specify strains. Animal studies suggest potential mechanisms involving serotonergic and GABAergic systems for specific strains (P72 and P77), but human evidence is limited. Overall, probiotics appear promising as adjunctive interventions for anxiety, but further large, strain-specific RCTs with long-term follow-up are needed.
Best studied probiotic strains
Lacticaseibacillus rhamnosus HN001
Evidence is high quality and strain-specific; studied in pregnant/postpartum women.
Psychobiotic formula (unspecified strains)
Specific strains not detailed; described as psychobiotics producing neuroactive substances.
Multispecies/multistrain probiotic supplements
Strain details often not specified; effects may vary by population and intervention duration.
P72 and P77 (experimental strains)
Evidence is preclinical and low certainty; human effects unknown.
Who may benefit
Safety
Probiotics were generally well tolerated with no significant increase in adverse events reported across studies. However, safety data are limited for some strains and populations, and long-term safety requires further study.
Limitations
Many studies do not specify probiotic strains, limiting strain-specific conclusions. High heterogeneity exists in study populations, probiotic formulations, dosages, and durations. Some evidence is from animal models or low-certainty studies. More large-scale, high-quality RCTs with long-term follow-up are needed to confirm efficacy and optimal strains for anxiety.
PubMed sources
| Study | Type | Year | PMID |
|---|---|---|---|
| Probiotics for the treatment of depression and anxiety: A systematic review and meta-analysis of randomized controlled trials. Clinical nutrition ESPEN |
Meta-analysis | 2021 | 34620373 |
| Probiotics in Psychosocial Stress and Anxiety. A Systematic Review. Journal of gastrointestinal and liver diseases : JGLD |
Systematic Review | 2020 | 32176751 |
| Exploring the acute and chronic effects of a multistrain probiotic supplement on cognitive function and mood in healthy older adults: a randomized controlled trial. The American journal of clinical nutrition |
Randomized Controlled Trial | 2025 | 40222448 |
| Psychobiotics Ameliorate Depression and Anxiety Status in Surgical Oncology Patients: Results from the Study. Nutrients |
Randomized Controlled Trial | 2025 | 40077722 |
| P77 and P72 and Their Mix-Live or Heat-Treated-Mitigate Sleeplessness and Depression in Mice: Involvement of Serotonergic and GABAergic Systems. Cells |
Research Study | 2025 | 41090775 |
| Effect of Lactobacillus rhamnosus HN001 in Pregnancy on Postpartum Symptoms of Depression and Anxiety: A Randomised Double-blind Placebo-controlled Trial. EBioMedicine |
Randomized Controlled Trial | 2017 | 28943228 |
| The efficacy of probiotics, prebiotics, and synbiotics on anxiety, depression, and sleep: a systematic review and meta-analysis of randomized controlled trials. BMC psychiatry |
Meta-analysis | 2025 | 41310510 |
| Probiotics and Subclinical Psychological Symptoms in Healthy Participants: A Systematic Review and Meta-Analysis. Journal of alternative and complementary medicine (New York, N.Y.) |
Meta-analysis | 2017 | 27841940 |
| Influence of Acute Multispecies and Multistrain Probiotic Supplementation on Cardiovascular Function and Reactivity to Psychological Stress in Young Adults: A Double-Blind, Randomized, Placebo-Controlled Trial. Psychosomatic medicine |
Randomized Controlled Trial | 2017 | 28498275 |
| Probiotic intake and mental health in healthy working adults: a systematic review and meta-analysis of randomized controlled trials. BMC psychology |
Meta-analysis | 2026 | 41501907 |