Recent research has revealed that bacteria that live within and on the body play both a central and critical role in normal physiological function. While many bacteria appear benign, and others can cause disease, many provide benefit to us, helping us digest food and producing chemicals important to our health. It appears likely that humans and other animals, having evolved with a significant bacterial exposure on all surfaces (including our digestive and reproductive tracts), have come to rely on bacteria for a range of biological functions.

Studies specifically examining bacteria are limited, and particularly in humans. However, evidence supports a complex interaction between bacteria, the environment (including the digestive tract and the food it contains), the gut wall, and physiological processes (including immune and endocrine regulation). An altered, or ‘dysbiotic’, bacterial community in the gut has been linked with a range of disorders, and include irritable bowel syndrome (IBS), and mental health disorders like depression and anxiety.

In this project we will ask participants to provide information about their diet, and physical and mental health, and provide a small faecal sample (for bacterial and metabolic assays), urine sample (for metabolic assays), saliva samples (for bacterial, metabolic, endocrine and immune assays), and a small hair sample (for endocrine assays).

We will compare the bacterial and physiological profiles of four different types of adults: 1) healthy adults; 2) adults with depression &/or anxiety disorders; 3) adults with irritable bowel syndrome (IBS); and, 4) adults with both depression &/or anxiety and IBS.

This will be the first project worldwide to compare the human bacterial and physiological profiles of healthy adults, adults with depression &/or anxiety disorders, adults with IBS, and adults with comorbid depression &/or anxiety and IBS.