A new analysis of existing studies combined with lab experiments suggests that a specific probiotic, Limosilactobacillus fermentum WIS32, might play a role in depression. The research had two parts: a meta-analysis of human studies and experiments in mice.
First, researchers looked at data from people with depression and found that they had lower levels of L. fermentum in their gut compared to healthy individuals. This suggests a possible link between this bacterium and depression.
Second, in mice with depression-like symptoms, giving them WIS32 improved their behavior. It also increased levels of serotonin and BDNF (a brain growth factor) in the hippocampus, a key area for mood. The probiotic reduced inflammatory markers and changed the gut bacteria in a positive way.
However, this is very early research. The human part only shows a correlation, not cause and effect. The main findings come from mice, which may not translate to people. No safety data or human trial results are available. Readers should not take this as proof that probiotics treat depression, but it does point to a promising area for future study.