Some research results suggest the effect of probiotics on the mood. The PubMed base was searched in the period from November to December 2017 to fi nd research on the impact of probiotics on the level of stress and depression. The following phrases were searched: probiotics and depression (149 publications), Lactobacillus and depression (118 publications), Bifi - dobacterium and depression (37 publications). 304 publications were found, including reviews, randomized trials, review papers and meta-analyses. The criterion for including works in the research review included the English language of the publication. Randomized trials were included in the research review that had a control group and concerned the infl uence of probiotics therapy and probiotic yoghurt on the mood in humans. Studies that have been carried out on animals, in a group of people with other disease entities ( > 1) or mental illness were excluded. The review did not include studies in which prebiotics were used or the form of probiotic bacteria administration was the yoghurt itself or milk. Finally, 5 publications were included in the research review. Previously conducted studies were carried out on small groups and concerned people with increased stress levels, depression or women exposed to postnatal depression. The most frequently conducted studies were carried out in groups which, apart from depression, also had another disease entity. The research was conducted on various age groups. The results of the studies that showed a positive effect of probiotic therapy on the mood were statistically insignifi cant or the change in the level of depression was low. Based on the research included in the review, it is diffi cult to draw unambiguous conclusions. The microbiome seems to have little effect on the mood.

Key words: depression, probiotics, Lactobacillus, Bifidobacterium.