The bacteroidetes/firmicutes ratio: a relevant biomarker of gut dysbiosis in major depression disorder? : a pilot cohort study

Abstract

BACKGROUND: Major Depressive Disorder (MDD) is one of the most prevalent conditions in the psychiatry and primary care services . It is considered the second leading cause of disability worldwide and is one of the most significant risk factors for suicide. Despite numerous treatments on the market, they are effective in less than half of the patients, and the high prevalence of this disorder remains unchanged. Many efforts have been made to understand this disorder; nevertheless, the exact pathophysiology remains unknown. In the last decade, the inflammatory theory has emerged, suggesting an intimate relationship between the alteration of gut microbiota and the development of depressive symptoms. Current literature reveals inconsistent results and indicates a long path for further research. OBJECTIVE: The aim of the study is to determine if young people with and increased Bacteroidetes/Firmicutes ratio in gut microbiota are more susceptible to develop aM DD over a five year period compared to those who do not have an increased ratio. Secondary objectives include assessing this susceptibility in relation to bacterial diversity and the observed differences in gut microbiota between depressive and non depressive participants STUDY DESIGN: The study is designed as a multicenter observational, analytic, prospective cohort study that will be carried out in the four basic health areas of Girona with a follow up of five years. PARTICIPANTS AND METHODS The study population will be formed by young adults between 18 and 30 years that meet the inclusion and none of the exclusion criteria. A total of 1452 participant s 363 subjects in the exposed group and 1089 in the non exposed group, will be probabilistically and randomly selected from the reference population, in proportion to each basic health area. To achieve the outlined objectives, their microbiota composition, relative abundance, and diversity will be analyzed in faecal samples using 16S rRNA gene sequencing