Background and aims: Recent mounting evidence suggest that probiotics supplementation can have a positive effect on mood and psychological symptoms such as stress and anxiety disorders. The majority of studies, however, rely on animal models, while clinical data are still inconsistent. In this systematic review, we examined if and to which extent probiotics can influence psychological stress and anxiety disorders.
Methods: The search of online databases Medline, PubMed, Scopus, Web of Science and clinical trials.gov provided relevant studies up to November 2019. We included double blind, randomized and placebo controlled or prospective studies, as well as studies measuring preclinical psychological symptoms of perceived stress and anxiety, before and after supplementation with a probiotic.
Results: Twelve studies met the inclusion criteria (3 on stress, 4 on anxiety, and 5 both on stress and anxiety), accounting for 1,521 participants. The improvement of stress, anxiety, and stress-anxiety was reported in 1/3, 3/4, and 2/5 studies, respectively.
Conclusions: Available studies suggest that probiotics may improve psychological symptoms associated particularly with anxiety. Further research needs to investigate whether probiotics also improve psychological stress disturbances.