Abstract

Bugs and Brains, the Gut and Mental Health Study: a mixed-methods study investigating microbiota composition and function in anxiety, depression and irritable bowel syndrome

BMJ Open. 2021 Mar 15;11(3):e043221. doi: 10.1136/bmjopen-2020-043221.

Carra A Simpson 1 2, Orli S Schwartz 3, Djamila Eliby 4 2, Catherine A Butler 5, Katherine Huang 6, Neil O'Brien-Simpson 5, Bridget L Callaghan 2 7, Stuart G Dashper 5, Paul R Gooley 6, Sarah Whittle 4 2, Nick Haslam 4, Julian G Simmons 4 2

 
     

Author information

  • 1Melbourne School of Psychological Sciences, The University of Melbourne Faculty of Medicine Dentistry and Health Sciences, Melbourne, Victoria, Australia carra.simpson@unimelb.edu.au.
  • 2Melbourne Neuropsychiatry Centre, The University of Melbourne Faculty of Medicine Dentistry and Health Sciences, Melbourne, Victoria, Australia.
  • 3Centre for Youth Mental Health, Orygen The National Centre of Excellence in Youth Mental Health, Parkville, Victoria, Australia.
  • 4Melbourne School of Psychological Sciences, The University of Melbourne Faculty of Medicine Dentistry and Health Sciences, Melbourne, Victoria, Australia.
  • 5Centre for Oral Health Research, Melbourne Dental School, Bio21 Institute, The University of Melbourne Faculty of Medicine Dentistry and Health Sciences, Melbourne, Victoria, Australia.
  • 6Department of Biochemistry and Molecular Biology, The University of Melbourne Bio21 Molecular Science and Biotechnology Institute, Parkville, Victoria, Australia.
  • 7The Department of Psychology, University of California Los Angeles, Los Angeles, California, USA.

Abstract

Introduction: Research has highlighted relationships between the micro-organisms that inhabit our gastrointestinal tract (oral and gut microbiota) with host mood and gastrointestinal functioning. Mental health disorders and functional gastrointestinal disorders co-occur at high rates, although the mechanisms underlying these associations remain unclear. The Bugs and Brains Study aims to investigate complex relationships between anxiety/depression and irritable bowel syndrome (IBS) in two ways. First, its primary component will compare the gut and oral microbiota in females with anxiety/depression and/or IBS relative to controls, and investigate underlying physiological, endocrine and immune factors, as well as associations with diet and psychosocial factors. In an ancillary component, the study will also investigate gastrointestinal and mental health symptoms in a larger sample, and explore relationships with diet, exercise, oral health, substance use, medical history, early life adversity and psychosocial factors.

Methods and analysis: The Bugs and Brains Study aims to recruit 160 females to the primary component: (1) 40 controls; (2) 40 participants with a depressive/anxiety disorder, but no IBS; (3) 40 participants with IBS, but no depressive/anxiety disorder and (4) 40 participants with both depressive/anxiety disorder and IBS. Participation is completed within 1 month, and involves comprehensive questionnaires, anthropometrics, a diagnostic clinical interview, collection of two saliva samples, and stool, urine and hair samples. This study aims to use a systems biology approach to characterise oral and gut microbial composition and function using 16S rRNA gene sequencing and nuclear MR spectroscopy. As part of the ancillary component, it will collect questionnaire data from 1000 participants aged 18-40 years, capturing mental health, gastrointestinal health, oral health, diet and psychosocial factors.

Ethics and dissemination: Approval was granted by the University of Melbourne Human Research Ethics Committee (#1749221). All participants voluntarily provided informed consent. Results will be published in peer-reviewed journals and presented at scientific conferences.

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