The bidirectional communication pathway between the gut microbiota and the central nervous system has been termed the brain-gut-microbiome axis. Increased investigation of this pathway has found the gut bacteria to impact metabolism and the brain, suggesting that modulating the microbiome may elicit change in mental health. The aim of this review is to discuss the current findings in both animal and human studies regarding the use of pro-, pre- and post-biotics in the prevention and treatment of depressive disorders. Studies show that modulating the bacteria in the gut may reduce inflammation, decrease stress hormone levels and adjust the levels of neurotransmitters in the brain. These changes consequently lead to the reduction of depressive symptoms and improvement in mood. While these results are promising, larger clinical trials are needed that include biochemical measurements and fecal microbiome analysis in addition to validated questionnaires. With this in mind, the authors conclude there is huge potential in the role of nutrition as a therapeutic target for neurological and mental health conditions.