Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials

Neurosci Biobehav Rev. 2019 Jul;102:13-23. doi: 10.1016/j.neubiorev.2019.03.023. Epub 2019 Apr 17.


With growing interest in the gut microbiome, prebiotics and probiotics have received considerable attention as potential treatments for depression and anxiety. We conducted a random-effects meta-analysis of 34 controlled clinical trials evaluating the effects of prebiotics and probiotics on depression and anxiety. Prebiotics did not differ from placebo for depression (d = -.08, p = .51) or anxiety (d = .12, p = .11). Probiotics yielded small but significant effects for depression (d = -.24, p < .01) and anxiety (d = -.10, p = .03). 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. This effect increased to medium-to-large in a preliminary analysis restricted to psychiatric samples (d = -.73, p < .001). There is general support for antidepressant and anxiolytic effects of probiotics, but the pooled effects were reduced by the paucity of trials with clinical samples. Additional randomized clinical trials with psychiatric samples are necessary fully to evaluate their therapeutic potential.

Keywords: Anxiety; Depression; Microbiome; Prebiotic; Probiotic.

Publication types

  • Meta-Analysis
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Systematic Review

MeSH terms

  • Anxiety Disorders / diet therapy*
  • Controlled Clinical Trials as Topic*
  • Depressive Disorder / diet therapy*
  • Gastrointestinal Microbiome*
  • Humans
  • Prebiotics*
  • Probiotics / therapeutic use*


  • Prebiotics