There is a growing body of evidence indicating that there may be a bidirectional gut microbiota–brain axis that can influence our mental health.  Although studies and data are limited by a cross-sectional design, small sample sizes, and multiple comparisons, research in microbiota composition in mental disease and health has accelerated during the last two years. 

 This study evaluates recent studies on the gut microbiome in mental health in humans and into the relevance of the bidirectional gut microbiota–brain communication in mood disorders in humans, such as the effect of probiotics on brain connectivity and mental health outcomes and pregnancy-related stress on gut microbiota in the newborn child.

However, research is still in its early stages, and further studies are needed to help clearly define the multi-role gut microbiota play in our mental health.  Importantly, this review further suggests that there is, although not clearly understood, a connection between gut health and mental health.