The first population-level study on the link between gut bacteria and mental health identifies specific gut bacteria linked to depression and provides evidence that a wide range of gut bacteria can produce neuroactive compounds. Jeroen Raes (VIB-KU Leuven) and his team recently published these results in the scientific journal Nature Microbiology.
Researchers at VIB-KU Leuven have identified several gut bacteria that may be linked to depression. Their findings provide further evidence that our intestinal bacteria produce substances with a potential impact on our mental health.
Jeroen Raes and his team at VIB-KU Leuven examined the faeces of 1,054 participants in the Flemish Gut Flora Project and combined this information with diagnoses of depression in the same group.
They discovered that the bacterial genera Coprococcus and Dialister are absent in the faeces of depressed individuals. These results were confirmed in a separate group of 1,063 participants in the Dutch LifeLines project and in a group of clinically depressed patients at University Hospitals Leuven.
Sara Vieira-Silva, Jeroen Raes, and Mireia Valles-Colomer, senior and first authors of the study. ©VIB
Gut bacteria and mental health: a controversial duo
Professor Jeroen Raes: "The link between gut flora and mental health is a controversial topic in microbiome research. The idea that substances produced by the microorganisms in our body have an impact on our brain – and, by extension, on our behaviour and emotions – is intriguing. But, thus far, this link has mostly been studied in animal models rather than human beings. In our population-level study, we were able to identify several groups of bacteria that seem to correlate with depression and quality of life in a diverse group of people."
We identified several groups of bacteria that seem to correlate with depression and quality of life in a diverse group of people.
In previous studies, Professor Raes and his team had already identified a microbial community or enterotype known as Bacteroides2, which is more prevalent among patients with Crohn's disease. In their current study, they were surprised to find that a similar enterotype is linked to depression and reduced mental health.
Professor Raes: "This study provides further evidence that Bacteroides2 may have a negative impact. Microbial communities linked to intestinal disease appear to share certain features with those linked to reduced mental health."
Jeroen Raes ©HLN
The researchers also developed a computer technique to identify which gut bacteria may have an impact on the human nervous system. By analysing the genome of more than 500 gut bacteria, they compiled a catalogue of bacteria that produce substances with a potential impact on our brain and nervous system. Some of these bacteria even produce quite a few of these substances.
Our new technique makes it possible to identify bacteria that may have an impact on our mental health and to unravel the underlying mechanism.
"Many substances that may influence the brain and the nervous system are produced in our gut," doctoral student Mireia Vallès-Colomer (VIB-KU Leuven) continues. "We wanted to find out which microorganisms might be involved in this process. Our toolbox makes it possible to identify bacteria that may have an impact on our mental health and to unravel the underlying mechanism. For one thing, we found that the ability of microorganisms to produce DOPAC – a substance linked to the neurotransmitter dopamine – is associated with a better mental quality of life."
The results of these bioinformatics analyses still need to be confirmed in further experiments, but they're already helpful in directing and accelerating future human microbiome-brain research.
Jeroen Raes and his team are currently preparing another sampling round for the Flemish Gut Flora Project, which will start next spring.
More information about the Flemish Gut Flora Project is available here.