This renewed interest in understanding the role of the microbiota beyond the digestive tract was spurred in 2007 when the Human Microbiome Project was launched. (Turnbaugh et al, 2007). With over one million different genes and a mass equal to that of the human brain, the genetic diversity of our bacterial commensals outnumbers the human genome by a factor of over 100 to one, and suggests the potential for the genetic variability in the GI environment to impact other body systems, including the central nervous system (CNS). A range of neurotransmitters relevant to mood and anxiety disorders including serotonin, GABA, acetylcholine and endocannabinoids are produced by intestinal microbiota (Dinan et al, 2013). This accruing data along with previous findings showing that pathological gut bacterium are capable of inducing changes in behavior (Lyte et al, 1998) and that early life stress, an established risk factor for major depression, induces changes in the microbiota (O'Mahony et al, 2007) underscore the potential importance of further examining the relationship between the microbiota and brain function with particular attention to the potential therapeutic implications for treatment of psychiatric conditions, such as depression