The outcome moves researchers one step nearer to utilizing microorganisms to address mood disorders.

Identifying the specific microbes that contribute to our health and disease has been a challenge, but a recent study in Finland has made progress in identifying a potential microbial culprit in some cases of depression. The study focused on how genetics and diet impact the microbiome, and the findings provide solid evidence of the clinical importance of this association. Research has been uncovering more connections between gut microbes and brain conditions such as autism and mood disorders. While it’s unclear if microbial deficits cause these disorders, there is a growing interest in using gut microbes and their byproducts as potential treatments. For example, a recent study showed that fecal transplants improved symptoms in depressed patients. The study in Finland was not specifically looking for microbes causing depression, but rather analyzing data from a larger health study. The researchers discovered that two sections of the human genome strongly influence gut microbiome composition, with one section related to lactose digestion and the other related to blood type. Additionally, the study found that two bacteria, Morganella and Klebsiella, which can cause infections in hospitalized patients, seemed to play a causal role in depression. Morganella, in particular, was significantly increased in individuals who later developed depression. This finding aligns with previous research showing a link between depression, inflammation, and Morganella. However, more research is needed as there are different forms of depression and various ways in which microbes may affect the disease. The ultimate goal is to identify a missing microbe that could be provided as a supplement, although eliminating Morganella from the gut is more challenging.