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

Quick answer

Probiotics, particularly certain strains of Lactobacillus and Bifidobacterium, have shown potential benefits in reducing symptoms of anxiety and depression. High-quality evidence supports strains such as Lactiplantibacillus plantarum, Lactobacillus rhamnosus HN001, Bifidobacterium longum NCC3001, and multispecies probiotic formulations in improving mood, anxiety, and depression symptoms in various populations. However, effects vary by strain, dose, population, and study design, and more research is needed to optimize treatment.

🔬 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

Lactiplantibacillus plantarum

High-quality RCTs demonstrated significant anxiety reduction in adults with mild to moderate anxiety (PMID: 40312029) and improved mood and immunity in healthy women (PMID: 40008414).

Studied for: Anxiety, depression, general mental wellbeing

Effects observed with doses around 9 log CFU/day over 6-12 weeks; mechanisms include neurotransmitter modulation and immune gene expression.

Lactobacillus rhamnosus HN001

RCT showed reduced postpartum depression and anxiety symptoms in women receiving HN001 during pregnancy and postpartum (PMID: 28943228).

Studied for: Postpartum depression and anxiety

May be particularly useful in perinatal mental health; administered from mid-pregnancy to 6 months postpartum.

Bifidobacterium longum NCC3001

RCT in IBS patients showed significant reduction in depression scores and altered brain activity related to emotional processing (PMID: 28483500).

Studied for: Depression in irritable bowel syndrome

Effects on depression but not anxiety; associated with changes in limbic brain regions.

Multispecies probiotic formulations

RCTs and meta-analyses indicate multispecies probiotics reduce anxiety and depression symptoms in healthy and clinical populations (PMID: 30991255, 40222448, 40077722).

Studied for: Anxiety, depression

Formulations vary; longer duration (≥8 weeks) and higher doses may improve efficacy.

Lacticaseibacillus paracasei and Lactobacillus acidophilus (in cultured milk drink)

RCT showed reduction in depression scores and increased serotonin levels in IBS patients with subthreshold depression (PMID: 38658619).

Studied for: Depression in IBS

Potential as adjunctive treatment in IBS-related mood disturbances.

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👥 Who may benefit

Adults with mild to moderate anxiety or depression symptoms Postpartum women experiencing depression and anxiety Patients with irritable bowel syndrome and comorbid depression Cancer patients undergoing gastrointestinal surgery and chemotherapy at risk of depression and anxiety Generally healthy adults seeking mood and mental wellbeing support Women with polycystic ovary syndrome experiencing depression and anxiety (limited evidence)

✅ 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

PMID 41129047 View study → PMID 31324280 View study → PMID 37513676 View study → PMID 40077722 View study → PMID 38402742 View study → PMID 40402417 View study → PMID 30860919 View study → PMID 39731509 View study → PMID 34620373 View study → PMID 37026368 View study → PMID 40076598 View study → PMID 41310510 View study → PMID 25470391 View study → PMID 28483500 View study → PMID 32377159 View study → PMID 28943228 View study → PMID 31307840 View study → PMID 40869419 View study → PMID 40312029 View study → PMID 38732599 View study → PMID 31858898 View study → PMID 30991255 View study → PMID 40222448 View study → PMID 40647242 View study → PMID 40008414 View study → PMID 28806201 View study → PMID 33955288 View study → PMID 40246176 View study → PMID 40175540 View study → PMID 41501907 View study → PMID 41515213 View study → PMID 41097163 View study → PMID 39519594 View study → PMID 17151594 View study → PMID 41155243 View study → PMID 41762172 View study → PMID 41599922 View study → PMID 35887166 View study → PMID 31992802 View study → PMID 37139495 View study → PMID 38658619 View study → PMID 37734624 View study →

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