Food and Behaviour Research

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Effects of Probiotics on Cognitive Reactivity, Mood, and Sleep Quality

Marotta A, Sarno E, Del Casale A, Pane M, Mogna L, Amoruso A, Felis GE, Fiorio M (2019) Front. Psychiatry  March 2019 Mar; 

Web URL: Read the research on Frontiers here


Recent demonstration that probiotics administration has positive effects on mood state in healthy populations suggests its possible role as an adjunctive therapy for depression in clinical populations and as a non-invasive strategy to prevent depressive mood state in healthy individuals.

The present study extends current knowledge on the beneficial effects of probiotics on psychological well-being, as measured by changes in mood (e.g., cognitive reactivity to sad mood, depression, and anxiety), personality dimensions, and quality of sleep, which have been considered as related to mood.

For this double-blind, placebo-controlled study 38 healthy volunteers assigned to an experimental or control group assumed a daily dose of a probiotic mixture (containing 
Lactobacillus fermentum LF16, L. rhamnosus LR06, L. plantarum LP01, and Bifidobacterium longum BL04) or placebo, respectively, for 6 weeks. Mood, personality dimensions, and sleep quality were assessed four times (before the beginning of the study, at 3 and 6 weeks, and at 3 weeks of washout).

A significant improvement in mood was observed in the experimental group, with a reduction in depressive mood state, anger, and fatigue, and an improvement in sleep quality. No between-groups differences were found.

These findings corroborate the positive effect of probiotics on mood state and suggest that probiotics administration may improve psychological well-being by ameliorating aspects of mood and sleep quality.


In this randomised controlled trial, participants taking a multi-strain probiotic for 6 weeks showed significant improvements from baseline on self-reported measures of depressive mood state, anger, fatigue, and sleep quality.  No such significant improvements were reported b those receiving placebo.

The results of this trial do not meet standard criteria for showing benefits from an experimental treatment.  That requires direct comparisons beween active and placebo groups to show a significant difference in 'change scores' from baseline, which was not the case here.

However, these findings are promising - and consistent with those from previous animal and some human studies.

The number of participants was relatively small, which matters, because for any given treatment effect size (i.e. the group difference) larger numbers would increase the statistical significance. 

Larger trials therefore have more 'statistical power' to detect genuine group differences - and could help to assess whether the benefits for mood, sleep and energy levels seen here within the group receiving probiotics may actually represent significant improvements compared with placebo treatment.

See the associated news article: