According to the results of a random-effects meta-analysis, there is a small, but significant, amount of evidence that supports the use of probiotics in the treatment of depression and anxiety.

The aim of the study was to determine the efficacy of both prebiotics and probiotics in the management of depression and anxiety. The authors searched Embase, MEDLINE, and PsychINFO for controlled clinical trials conducted in humans that analyzed the effects of prebiotic or probiotic monotherapy on depression or anxiety. A total of 34 controlled clinical trials met the study author’s inclusion criteria

According to their analysis, prebiotics did not have an overall effect on either depression or anxiety. No differences were observed between patients who received prebiotics vs placebo in the 5 trials that assessed its effect on depression (d = − 0.08, P =.51) and the 4 trials that assessed its effect on anxiety (d = 0.12, P =.11).

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With regard to probiotics, results showed a small but significant effect on depression (d = − 0.24, P <.01). Of the 24 trials assessed, 23 reported improvement  in depression in patients who received probiotics compared with placebo. “Sample type was a moderator for probiotics and depression, with a larger effect observed for clinical/medical samples (d = − .45, P <.001) than community ones,” the study authors stated. They added, “This effect increased to medium-to-large in a preliminary analysis restricted to psychiatric samples (d = − .73, P <.001).

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Results of the analysis also showed that probiotics had a small but significant effect on anxiety (d = − 0.10, P =.03). In 22 of the 23 studies analyzed, probiotic use was associated with decreased anxiety compared with placebo.

According to the results of this meta-analysis, there is a modest amount of evidence supporting the use of probiotics for the management of depression and anxiety. However, the study authors concluded, “the pooled effects were reduced by the paucity of trials with clinical samples.” They added that additional studies are needed to fully understand the therapeutic effect of probiotics.

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This article originally appeared on MPR