Overall, 11 of the 21 studies showed a positive effect on anxiety symptoms by regulating intestinal microbiota, meaning that more than half (52%) of the studies showed this approach to be effective, although some studies that had used this approach did not find it worked. Of the 14 studies that had used probiotics as the intervention, more than a third (36%) found them to be effective in reducing anxiety symptoms, while six of the remaining seven studies that had used non-probiotics as interventions found those to be effective -- a 86% rate of effectiveness. Some studies had used both the IRIF (interventions to regulate intestinal microbiota) approach and treatment as usual. In the five studies that used treatment as usual and IRIF as interventions, only studies that had conducted non-probiotic ways got positive results, that showed a reduction in anxiety symptoms. - www.sciencedaily.com