Gut microbiota plays a role in infants’ neuronal development by secreting molecules involved in neuronal and immunological signaling. That relationship between the gut and the brain is known as the gut-brain axis.
The first months of life are important in the process of establishing a healthy gut microbiota. The bacteria that first colonize a child’s gut come from the mother’s gut microbiome, vaginal microbiota or from the mother’s skin microbiota and the environment in the case of a caesarian birth, as well as from breastfeeding. Later in the life, the child’s surroundings will shape the bacterial community found in their intestine.
Previous research has highlighted the close link between the gut microbiota and neuronal activity and disorders. While there is a lack of studies aiming to understand how the gut microbiota evolves during infancy to cause neuronal disorders, Amy Loughman’s recently published article ‘Gut microbiota composition during infancy and subsequent behavioural outcomes’ considers that subject.
For the study, Pr. Peter Vuillermin and his colleagues looked at the Barwon Infant study and used a subcohort of 201 Australian-born children. They analyzed the fecal microbiota composition of these 201 children at 1, 6 and 12 months of age. Then, they assessed the children’s behaviour at the age of 2 using the Child Behaviour Checklist, which consists of 99 questions answered by the children’s parents.
Behavioural disorders in childhood include attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), autism spectrum disorder (ASD) and learning disorders.
In the unselected birth cohort, the researchers identified 22 cases of elevated behavioural disorders and observed a variation of Prevotella bacteria that associated with these disorders, in particular internalizing problems. Indeed, the bacterial genus was detected in only 4% of children with behavioural disorders compared to 44% of healthy children. In this study, it would seem that low abundance of Prevotella at 12 months in the microbiota could be a predictor of behavioural disorders during childhood. The team subsequently tried to find the cause of this change in gut microbiota and so evaluated the factors that could trigger the change. In the cohort under study, the reduction in Prevotella levels was directly associated with antibiotic intake between 6 and 12 months of age.
Delivery mode (vaginal or cesarian), breastfeeding, the environment, owning or being in contact with animals and food diversification, are all factors that influence the gut microbiota’s composition. In this study, Peter Vuillermin and his team, showed how antibiotic use during a child’s first 6 to 12 months of life could have an impact on the levels of bacteria and could be linked to the development of behavioral disorders at a later stage.
In conclusion, the results of numerous studies have highlighted the gut microbiota’s role in influencing mental health. Research is, now, focussing on how to identify “types” of microbiota composition that may be associated with the development of neurological disorders, as well as potential composition modulators, that could influence their development or on the contrary prevent or alleviate symptoms or even treat these types of illnesses. However, it is important to note that the intestinal microbiota is only one of many factors that is associated with the development of neurological disorders.
 Barwon Infant study is a cohort of children born in Australia followed over several years.
Reference: Loughman A., Ponsonby A.L., O’Hely A. et al. Gut microbiota composition during infancy and subsequent behavioural outcomes. EBioMedecine. 2020; 52: 102640. https://doi.org/10.1016/j.ebiom.2020.102640