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Review
. 2020 Apr 1:266:429-446.
doi: 10.1016/j.jad.2020.01.124. Epub 2020 Jan 22.

Feeling down? A systematic review of the gut microbiota in anxiety/depression and irritable bowel syndrome

Carra A Simpson  1 , Andre Mu  2 , Nick Haslam  3 , Orli S Schwartz  4 , Julian G Simmons  5
Affiliations
Review

Feeling down? A systematic review of the gut microbiota in anxiety/depression and irritable bowel syndrome

Carra A Simpson et al. J Affect Disord. .

Abstract

Background Anxiety/depression and irritable bowel syndrome (IBS) are highly prevalent and burdensome conditions, whose co-occurrence is estimated between 44 and 84%. Shared gut microbiota alterations have been identified in these separate disorders relative to controls; however, studies have not adequately considered their comorbidity. This review set out to identify case-control studies comparing the gut microbiota in anxiety/depression, IBS, and both conditions comorbidly relative to each other and to controls, as well as gut microbiota investigations including measures of both IBS and anxiety/depression. Methods Four databases were systematically searched using comprehensive search terms (OVID Medline, Embase, PsycINFO, and PubMed), following PRISMA guidelines. Results Systematic review identified 17 studies (10 human, 7 animal). Most studies investigated the gut microbiota and anxiety/depression symptoms in IBS cohorts. Participants with IBS and high anxiety/depression symptoms had lower alpha diversity compared to controls and IBS-only cohorts. Machine learning and beta diversity distinguished between IBS participants with and without anxiety/depression by their gut microbiota. Comorbid IBS and anxiety/depression also had higher abundance of Proteobacteria, Prevotella/Prevotellaceae, Bacteroides and lower Lachnospiraceae relative to controls. Limitations A large number of gut microbiota estimation methods and statistical techniques were utilized; therefore, meta-analysis was not possible. Conclusions Well-designed case-control and longitudinal studies are required to disentangle whether the gut microbiota is predicted as a continuum of gastrointestinal and anxiety/depression symptom severity, or whether reported dysbiosis is unique to IBS and anxiety/depression comorbidity. These findings may inform the development of targeted treatment through the gut microbiota for individuals with both anxiety/depression and IBS.

Keywords: Anxiety; Depression; Gut microbiota; Irritable bowel syndrome; Microbiome; Systematic review.

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Conflict of interest statement

Declaration of Competing Interest None

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