Psychobiotics in the treatment of anxiety and depression: an integrative review

Abstract

Interest in the relationship between the gut microbiome and mental health is growing, especially in anxiety and depression, as probiotics, microorganisms residing in the gut, influence the balance of physiology and mental health. Anxiety presents symptoms such as fear, distress, excessive thoughts and worries, while depression manifests as lack of motivation, feelings of inadequacy, insomnia or excessive sleep. An integrative review using the databases SciELO, EBSCO and PubMed included clinical trials, experimental and observational studies whose primary outcome evaluated the use of psychobiotics in the treatment of anxiety and depression. The search resulted in 2355 records published between 1998 and 2025, with 21 studies selected for review, published between 2017 and 2025. The composition of probiotics in the intervention mainly included strains of Lactobacillus spp. and Bifidobacterium spp. Most studies were conducted in China and the United Kingdom. The screening included 1384 patients, the majority, 65.25% (n=903), women, and one study stood out with a larger number of participants (n=200). The longest study had a 16-week analysis period, with most lasting 8 weeks. Major depressive disorder appeared in 66.67% (n=14) of the studies. The results of the observed clinical trials were positive, both for psychobiotics alone and in combination with traditional pharmacotherapy, showing a reduction in symptoms and their severity, improved quality of life, and well-being of patients. No significant side effects related to psychobiotics were observed. This research demonstrates that psychobiotics are a promising adjunctive therapy approach for the treatment of depression and anxiety based on symptom improvement.

Keywords: probiotics; mental disorders; complementary therapies.