Study finds probiotic no better than placebo for Parkinson’s anxiety

A small clinical trial testing whether a probiotic supplement could ease anxiety in people with Parkinson’s disease found that it was no better than a placebo.

However, patients given the supplement showed significant improvements on cognitive tests compared with those given the placebo. The researchers cautioned that this finding should be interpreted cautiously, and called for further studies to explore whether probiotics may help improve cognition in Parkinson’s.

“While no group differences were observed for neuropsychiatric symptoms following the 12-week intervention, the potential cognitive benefits seen in the probiotic group warrant further investigation,” they wrote in the study, “Probiotic supplementation for anxiety symptoms in people with Parkinson’s disease: a randomized, double-blind, placebo-controlled trial,” which was published in npj Parkinson’s Disease.

Anxiety — uncontrollable worry or fear — is a common nonmotor symptom of Parkinson’s that can cause substantial distress. Although talk therapy and medication may help manage anxiety, these available therapies don’t work for everyone. Researchers are actively searching for new ways to help ease anxiety.

Probiotics are a broad class of supplements containing living bacteria that are thought to be beneficial for health. More than 20 clinical trials have tested whether various probiotic supplements can ease anxiety in the general population, with some reporting promising effects. A few studies have also tested whether probiotics can help ease various symptoms of Parkinson’s, but there’s minimal data on whether probiotics may help ease anxiety in people with this neurological disease.

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Scientists at the University of British Columbia conducted a Phase 2 clinical trial (NCT03968133) with the main goal of testing whether probiotics might be an effective means of treatment for anxiety in Parkinson’s. The researchers said the study “represents the first [randomized clinical trial] specifically designed to evaluate the effects of probiotic supplementation on [Parkinson’s]-related anxiety.”

The study enrolled 70 people with Parkinson’s, of whom 61 completed the trial. All reported substantial anxiety at the study’s start. Participants were randomly assigned to receive a placebo or the probiotic Ecologic BARRIER, sold by Winclove Probiotics. The scientists said they chose this probiotic because it has been shown to be generally safe and to offer promising psychiatric benefits in trials of people without Parkinson’s.

The researchers used a disease-specific measure called the Parkinson Anxiety Scale (PAS) to track anxiety. Results indicated that patients given the probiotic supplement tended to report less anxiety over the course of the 12-week-long study. However, patients given the placebo also reported substantial easing of anxiety, with statistical analyses showing no significant differences between the two groups.

“Both the probiotic and placebo groups demonstrated substantial within-group improvements on the PAS, with no evidence of a between-group difference,” the researchers wrote. They noted that other factors, such as frequent check-ins with members of the trial team, may have contributed to the reduction in anxiety, regardless of whether patients received the probiotic or placebo.

Most secondary measures in the study also showed no statistically significant differences between patients receiving the probiotic and those receiving the placebo. There was one exception, however: Patients who took the probiotic showed significant improvements on the Montreal Cognitive Assessment (MoCA) by an average of slightly more than one point compared with patients given the placebo.

The MoCA is a widely used measure of cognitive function, so the data suggest that probiotics may improve cognitive abilities in Parkinson’s patients. The researchers stressed the need for caution when interpreting the results, since the study was not designed to assess cognitive impact and most patients had high MoCA scores, indicating minimal cognitive impairment. The cognition data “should be considered preliminary and hypothesis-generating,” they wrote.