 This study will be an 8-week open-label pilot study examining subjective and objective changes in mood, anxiety, cognition, and sleep before and after the introduction of a probiotic supplement containing Lactobacillus helveticus and Bifidobacterium longum in 10 treatment-naïve participants diagnosed with major depressive disorder MDD. In order to examine the full composition of the micro biome, the investigators will also be collecting and analyzing fecal samples as well as blood samples to examine changes in plasma levels of inflammatory markers, 5-HT, and tryptophan in order to look at possible underlying mechanisms of any changes seen. 