Simpson CA¹, Mu A², Haslam N³, Schwartz OS⁴, Simmons JG⁵. J Affect Disord. 2020 Jan 22;266:429-446. doi: 10.1016/j.jad.2020.01.124. [Epub ahead of print]

Author information

1 Melbourne School of Psychological Sciences, The University of Melbourne, 12th floor Redmond Barry Building, Parkville, VIC, Australia; Melbourne Neuropsychiatry Centre, The University of Melbourne and Melbourne Health, VIC, Australia. Electronic address: carra.simpson@unimelb.edu.au.

2 Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, The University of Melbourne, VIC, Australia; Doherty Applied Microbial Genomics, Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, The University of Melbourne, VIC, Australia; Microbiological Diagnostic Unit Public Health Laboratory, at the Peter Doherty Institute for Infection and Immunity, The University of Melbourne, VIC, Australia.

3 Melbourne School of Psychological Sciences, The University of Melbourne, 12th floor Redmond Barry Building, Parkville, VIC, Australia.

4 Orygen, The National Centre of Excellence in Youth Mental Health; Centre for Youth Mental Health, The University of Melbourne, VIC, Australia.

5 Melbourne School of Psychological Sciences, The University of Melbourne, 12th floor Redmond Barry Building, Parkville, VIC, Australia; Melbourne Neuropsychiatry Centre, The University of Melbourne and Melbourne Health, VIC, Australia.

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.