The gut-brain relationship: Investigating the effect of multispecies probiotics on anxiety in a randomized placebo-controlled trial of healthy young adults

J Affect Disord. 2019 Jun 1;252:271-277. doi: 10.1016/j.jad.2019.04.043. Epub 2019 Apr 8.


Intro: There has been an increased interest in understanding the therapeutic effect of gut-microbiota on health, particularly in mental health. However, limited research into the connection between gut-microbiota and mental health makes this study an important endeavor in exploring the effect of gut-microbiota, through probiotics intervention, on mental health like anxiety and factors related to anxiety (e.g., anxiety control, affect, negative mood regulation, and worry).

Method: Healthy college students (N = 86; 75.6% female), average age of 20.59, participated in a double-blind, placebo-control, and randomization-control study. Eligible participants completed a baseline survey before being assigned to a condition, which consisted of four probiotics conditions and one placebo condition. After 28 days of daily intake, the participants returned to complete their exit survey.

Result: Probiotics were observed to improve panic anxiety, neurophysiological anxiety, negative affect, worry, and increase negative mood regulation. Furthermore, post hoc analyses revealed that the CFU (colony-forming unit) level was more effective than species counts in accounting for the number of significant improvements. A ceiling effect was detected in the study, participants with high distress reported higher number of improvements than those with normative distress.

Conclusion: Overall, this study is the first to examine the effect of CFU and species count on probiotics' efficacy. The study's finding suggested that probiotics may have the therapeutic potential to treat anxiety, however, further research is necessary to make that determination.

Keywords: Affect; Anxiety; Gut-brain axis; Probiotic; Psychobiotics.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Affect / physiology
  • Anxiety Disorders / microbiology*
  • Anxiety Disorders / therapy*
  • Brain / microbiology*
  • Double-Blind Method
  • Female
  • Gastrointestinal Microbiome*
  • Humans
  • Male
  • Probiotics / therapeutic use*
  • Treatment Outcome
  • Young Adult