مقالات پذیرفته شده در نهمین کنگره بین المللی زیست پزشکی
The Efficacy of Lactobacillus and Bifidobacterium in Depressive: A Brief Review
The Efficacy of Lactobacillus and Bifidobacterium in Depressive: A Brief Review
mahdis mohammadjani,1,*
1. End of Rajaee Shahr, the intersection of Mozen and Esteghlal Blvd., Amirul Mominin University Complex (AS)
Introduction: Depression is one of the most common mental disorders, affecting a significant number of people worldwide and imposing a heavy burden on healthcare systems (1,2). Despite the availability of conventional treatments, the inadequate response of some patients and the side effects of medications have increasingly highlighted the need for complementary and innovative therapeutic approaches (1,3).
The gut microbiota, composed of trillions of microorganisms, plays a vital role in metabolism, immunity, and communication with the nervous system through the gut-brain axis (4). Due to its significant influence on the regulation of the central nervous system, the gut microbiota is often referred to as the "second brain" (5). The gut-brain axis acts as a bidirectional communication channel between the gastrointestinal microbiota and the human nervous system (6,7). Depression is closely linked to the gut microbiota, and its dysregulation can contribute to the exacerbation of depression through the gut-brain axis. Probiotics, particularly Lactobacillus and Bifidobacterium, are recognized as novel therapeutic agents in this context (3,8). This article reviews the effectiveness of these probiotics in the management of depression and their mechanisms of action.
Methods: A literature search was conducted using the Google Scholar database with keywords such as "Bifidobacterium in depression treatment," "Lactobacillus in depression treatment," and "gut-brain axis in depression." The inclusion criterion was studies published between 2019 and 2025. Based on this, 11 articles were selected out of 32 extracted records. The type of study (review or original research) was not a selection criterion; only thematic relevance was used for selection. Key data from these articles were extracted and summarized narratively.
Results: Analysis of the reviewed studies reveals promising evidence regarding the efficacy of probiotics from the Lactobacillus and Bifidobacterium genera in managing depressive symptoms. A randomized, double-blinded, clinical trial conducted by Haghighat et al. on hemodialysis patients demonstrated that 12 weeks of synbiotic supplementation (a combination of probiotics and prebiotics {bacterial food}) containing four species—L. acidophilus, B. bifidum, B. lactis, and B. longum—resulted in a significant reduction in depressive symptoms compared to the placebo group. This effect was reported to be more pronounced in patients who had depression at the beginning of the study (9). Other studies also indicated that daily probiotic intake at a dose of 3× 109 to 9×1011 CFU for 4 to 8 weeks, as an adjunctive therapy alongside conventional antidepressants, can lead to greater improvement in depressive symptoms (10).
The observed effects are mediated through several biological mechanisms. The most significant of these mechanisms include immune system modulation, reduction of inflammation, and regulation of the hypothalamic-pituitary-adrenal (HPA) axis activity (3,5,11). Furthermore, studies show that supplementation with Lactobacillus and Bifidobacterium probiotics contributes to the restoration of gut microbiota composition (5,8). A study by Tsai et al. investigated the effects of three Lactobacillus species (L. rhamnosus GMNL-74, L. acidophilus GMNL-185, and L. plantarum GMNL-141) on depression in mice, which resulted in significant improvement. Proposed mechanisms for this effect include the regulation of amino acid and fatty acid metabolism, as well as the strengthening of the blood-brain barrier (11).
Although these findings are promising, significant heterogeneity is observed across studies, primarily attributed to the following factors: the diversity of probiotic strains used and variations in dosage (10,11).
Conclusion: The findings of this review indicate that supplements containing bacteria from the Lactobacillus and Bifidobacterium genera hold significant potential as a complementary strategy for managing depressive symptoms. The efficacy of these probiotics is exerted through multiple mechanisms, including modulation of gut microbiota composition, reduction of inflammatory markers, strengthening of the blood-brain barrier, and regulation of the HPA axis.
However, heterogeneity in study results underscores the necessity to consider factors such as specific bacterial species and optimal dosage. Multi-strain probiotic formulations, especially when combined with prebiotics (synbiotics), appear to have stronger effects compared to single-strain interventions.
Translating these findings into clinical application requires future studies with more robust designs and larger sample sizes. Overall, targeting the gut-brain axis through probiotics represents a promising approach for developing more personalized therapies for mood disorders.