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Intestinal Flora Interventions and Anxiety

10/22/2019 3:50:10 PM
As many as one in 3 people will be affected by anxiety symptoms during their lifetime. A growing body of research suggests that the intestinal flora can modulate anxiety and mood via the gut-brain axis (a communication network that involves the gastrointestinal, immune, endocrine, and nervous systems). However, whether or not anxiety can be improved by modulating the gut microbiota is still up for debate. That is the question researchers aimed to answer with a systematic review published in 2019.

Review examines intestinal flora and anxiety connection

The review included 21 randomized controlled trials published before July of 2018. The 21 studies involved 1503 subjects. Most of the studies (15) used probiotics as the intervention, whereas 6 used non-probiotic interventions. Most interventions ranged from 4-8 weeks. Outcome measures included a range of questionnaires to assess anxiety symptoms. 

Probiotic interventions ranged from a single type of probiotic (mostly Lactobacillus) to 3 or more types of probiotics (e.g., Lactobacillus, Streptococcus, Bifidobacterium). Non-probiotic interventions included a low-FODMAP diet, short-chain fructooligosaccharides (scFOS), trans-galactooligosaccharides, and other dietary modifications.

Non-probiotic dietary interventions show promise for anxiety symptoms

Based on the Cochrane risk of bias and the Jadad scale, the overall quality of the 21 articles was high. Overall, 11 of the 21 studies (52%) showed that regulating the intestinal microbiota had a positive effect on anxiety symptoms. However, the non-probiotic interventions were dramatically more effective than the probiotic interventions. Of the 7 studies that used non-probiotics as an intervention, 6 (86%) were effective. Of the 14 studies that used probiotics as an intervention, only 5 (36%) were effective.
In addition to the differing efficacy between probiotic and non-probiotic interventions, there was also a difference between healthy participants and those with a chronic illness. Of the 6 articles that involved healthy individuals, 4 (67%) showed positive effects on anxiety. Of the 10 articles that involved subjects with irritable bowel syndrome (IBS), 5 (50%) showed positive effects on anxiety. Of the 5 articles that involved subjects with other chronic diseases (i.e., chronic fatigue syndrome, rheumatoid arthritis, or obesity), only 2 (40%) showed positive effects on anxiety.  
The authors of this systematic review concluded that regulating the intestinal flora may alleviate anxiety symptoms in some patients, with non-probiotic interventions demonstrating greater efficacy than probiotic interventions. There is still much to discover about the specifics of which patient populations will benefit most from modulation of the intestinal flora.          
Yang B, Wei J, Ju P, Chen J. Effects of regulating intestinal microbiota on anxiety symptoms: A systematic review. Gen Psychiatr. 2019; 32.