- Design
- Single-centre, double-blind, placebo-controlled randomised trial
- Population
- 66 adults with moderately active psoriatic arthritis on stable therapy
- Primary outcome
- PASDAS low disease activity or remission at week 12
- Effect
- 43% vs 65%; OR 0.4 (95% CI 0.13 to 1.18)
A single-centre, double-blind, placebo-controlled trial randomised 66 patients with psoriatic arthritis of moderate activity, on stable treatment, to a multispecies Lactobacillus and Bifidobacterium probiotic or placebo for 12 weeks. Published in Rheumatology on 1 October 2026.
In the 56 analysed, low disease activity or remission without a treatment change was reached by 43% on probiotic and 65% on placebo (OR 0.4, 95% CI 0.13 to 1.18). There were no differences in gut permeability markers, immune cells or stool microbiome. No serious product-related adverse events occurred.
The trial was small and short, so it cannot exclude a modest benefit, and the placebo group in fact did numerically better. It gives no support to recommending probiotics as a treatment for psoriatic arthritis, a question patients often ask.
- Advise patients that probiotics did not improve psoriatic arthritis activity in this trial
- Do not delay or replace disease-modifying treatment with supplements
- Discuss diet in terms of weight and cardiovascular risk, which do affect outcomes
- Expect placebo responses in patient-reported measures in any short trial
Why it matters
Patients commonly ask about gut-targeted supplements; this gives a trial-based answer.
Don't overread it
A small 12-week trial; it cannot rule out a small effect of other probiotic formulations.
The statistics, in plain English
An odds ratio of 0.4 with an interval from 0.13 to 1.18 crosses 1.0, so the result is compatible with no difference; it is not evidence that probiotics cause harm.
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