Do probiotics help with anxiety? What the research does and doesn't show

The evidence doesn't support probiotics as a treatment for anxiety. The meta-analyses disagree: one pooled 12 trials and found no significant difference from placebo; another pooled 29 and found a small reduction its authors called preliminary. None identifies a strain, dose or duration that works.

What the evidence doesn't support

It doesn't support probiotics as a treatment for anxiety, panic disorder or generalized anxiety disorder, and it doesn't support the idea that any particular probiotic "works for anxiety." No review identifies a strain, a dose or a length of use that does. Personal accounts, however sincere, are not trials: without a placebo group there is no way to separate the supplement from everything else that changed.

The trials also don't tell you about the product on a shelf. Each tested named strains at stated amounts, and the best-known review of the field found that probiotic effects are strain-specific and purpose-specific and that many products have no trial of their own. A product that lists species without strain codes can't borrow any result below.

What the trials found

A 2018 meta-analysis pooled 12 randomized trials with 1,551 participants, rated all of them low or moderate risk of bias, and found no significant difference between probiotics and placebo on anxiety rating scales, in the pooled analysis or in any subgroup. Dropping one study made the result marginally significant. The authors called the evidence insufficient.

A 2023 meta-analysis pooled 29 randomized trials with 2,035 participants and reached a different answer: probiotics, and synbiotics (probiotic plus prebiotic), reduced anxiety scores, while prebiotics alone did not. The effect size was small, the authors called their own findings preliminary, and they reported no consensus on the best dose, duration, type of product or strain.

A 2019 meta-analysis of 34 controlled trials of prebiotics and probiotics on depression and anxiety found a small effect of probiotics on anxiety scores (d = -0.10, p = 0.03). A 2025 meta-analysis limited to people with a clinical diagnosis pooled 9 trials of probiotics for anxiety and found a moderate reduction versus placebo (SMD -0.59, 95% CI -0.98 to -0.19), with high heterogeneity: the trials differed a lot in who was studied, what was given and for how long. A 2017 meta-analysis of 7 trials in healthy volunteers found a small improvement in a combined score of everyday depression, anxiety and stress symptoms (SMD 0.34).

Review	Trials	People	Result for anxiety versus placebo
2018 meta-analysis	12	1,551 adults	No significant difference
2019 meta-analysis	34 (depression and anxiety)	mixed	Small effect (d = -0.10)
2023 meta-analysis	29	2,035 adults	Small reduction, called preliminary
2025 meta-analysis	9 (anxiety)	clinically diagnosed	Moderate reduction, high heterogeneity
2017 meta-analysis	7	healthy volunteers	Small improvement in combined symptom score

The gap between 12 trials finding nothing and 29 finding a small effect comes down to which trials were counted, which scales were used, and a small pooled effect that sits close to zero. That is a reason to wait for larger, strain-specific trials, not a reason to pick a winner. We found no trial in these reviews that says how long to take a probiotic for anxiety or which strain to choose.

Probiotic effects are strain-specific, so a result for one named strain is not a result for "probiotics" in general, and a product that lists species without strain codes can't borrow it. See what the research shows across probiotics and how to choose a probiotic.

Questions people ask

Does probiotics help with anxiety?

Not reliably, on the evidence so far. One meta-analysis of 12 trials found no significant difference from placebo; another of 29 found a small reduction that its authors called preliminary. Neither shows that a probiotic treats anxiety.

Can probiotics help anxiety and depression?

Meta-analyses report small average improvements in scores for both, larger in people with a clinical diagnosis, and with high variation between trials. See what the research shows for depression. Score changes in a trial are not the same as treating either condition.

Which probiotic should I choose for anxiety?

The reviews above don't rank strains. The 2023 authors reported no consensus on the optimal strain, dose or duration, so any ranked list of probiotics for anxiety goes beyond the evidence.

Is there a probiotic dose or length of use that works?

No dose or duration has been established. Trials varied widely, and a review of dose-response studies found that whether more does more depends on the outcome (see probiotics dosage).

When to talk to a doctor

Anxiety that interferes with daily life, work or sleep is worth raising with a doctor. A probiotic is not a treatment for anxiety, panic disorder or generalized anxiety disorder, and nothing above supports using one in place of an evaluation, therapy or medication a doctor recommends. If you take prescription medication, are pregnant or nursing, or have a weakened immune system, ask a doctor before adding any supplement (see who should not take probiotics).