A new study examining more than 1,000 people has identified two specific types of bacteria that are strongly linked to mood and depression.
One of the most exciting and least understood areas of gut microbiome research is the link between gut bacteria and mental health.
A growing body of evidence is uncovering how the bacteria in the gut can influence the brain (known as the gut-brain axis), from PTSD to brain inflammation.
Now, researchers have linked two specific types of bacteria in the gut microbiome to depression.
The team analyzed the association between fecal microbiome data and diagnosed clinical depression in 1,054 individuals enrolled in the ongoing Flemish Gut Flora Project.
They focused in on specific groups of bacteria that were positively (increased) or negatively correlated (decreased) with depression. The researchers found two species of gut bacteria, Coprococcus and Dialister, were consistently absent or seen at lower levels than normal in study participants suffering from depression, regardless if antidepressant treatment.
The results were then validated in a different cohort of 1,063 individuals from the Dutch LifeLinesDEEP cohort and in a cohort of clinically depressed patients at the University Hospitals Leuven, Belgium.
Interestingly, a group of bacteria (known as an enterotype) called Bacteroides2 that has previously been linked to Crohn’s disease was found to be more prevalent in patients with depression.
Finally, the authors created a computational technique allowing them to identify gut bacteria that could potentially interact with the human nervous system, the idea being to create a catalog of neuroactive bacteria in the human gut. They found certain types of gut bacteria that could make a wide range of chemicals that interact with the brain.
The researchers hope that this catalog will help other researchers identify specific types of bacteria involved in mental health and the specific ways in which they affect the host. One example the team found is that the ability of gut bacteria to produce DOPAC, a metabolite of the human neurotransmitter dopamine, was associated with better mental quality of life.
While no one is claiming a direct causal link between these bacteria and depression (yet), the findings add more evidence to link gut microbiome dysbiosis and intestinal inflammation with mental health.
Reference:
Valles-Colomer, Mireia, et al. "The neuroactive potential of the human gut microbiota in quality of life and depression." Nature microbiology (2019): 1.
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