The relationship between mental health states and the gut microbial community is referred to as the gut-brain axis. This relationship is bi-directional meaning that the brain influences the gut microbiota and the gut microbiota influences that brain. The gut microbiota influences the brain through systemic means, using small molecules such as neurotransmitters, and through neural means, using sympathetic nerves. It is hypothesized that the gut microbiota can influence mental conditions such as depression, anxiety, and even autsim spectrum disorders. The brain influences the gut microbiota through neural means specifically through the vagus nerve and other sympathetic nerves, and also through the use of small molecules. By working towards a symbiotic gut microbiome, it is believed that mental health states are improved. There is believed to be a link between our microbiota and potentially treating schezophrnisa, bi-polar disorder, PTSD, OCD, eating disorders, and other mental heath conditions. This topic is still very widely controversial but current evidence shows lots of promise.