Scientists have identified a new link between the gut microbiome and brain chemistry, after a study found that the neuroactive potential of bacteria in the human gut was associated with levels of key chemical messengers in specific regions of the brain. The research, published in Molecular Psychiatry and reported on September 1, 2026, examined whether microbial pathways in the gut were connected to GABA, glutamate and the balance between them in healthy young women.
The team studied 61 healthy participants aged 17 to 25. Researchers used proton magnetic resonance spectroscopy to measure brain chemistry in three regions, while stool samples were analysed using shotgun metagenomic sequencing to assess the genetic capacity of gut microbes to carry out metabolic processes involving GABA, glutamate, short-chain fatty acids and other neuroactive compounds.
Region-specific patterns emerged across the brain
The findings showed that the relationship between the gut microbiome and brain chemistry was not uniform. Different microbial pathways were associated with GABA, glutamate and the excitatory/inhibitory balance in different brain regions, suggesting a more regionally specific gut-brain picture than previously understood.
According to the study, the inferior occipital gyrus showed the broadest range of associations, including pathways involved in glutamate degradation, GABA metabolism, short-chain fatty acids, inositol and p-cresol. The anterior cingulate cortex showed a distinct pattern involving microbial glutamate and propionate pathways, while the dorsolateral prefrontal cortex showed a more selective association with a microbial GABA-production pathway.
Psychological wellbeing also showed associations
The researchers also explored links with psychological wellbeing and found associations between specific gut microbial pathways and self-reported anxiety, depressive symptoms and sleep quality. A GABA-related pathway was associated with trait and social anxiety, while pathways involved in tryptophan metabolism were linked to depressive symptoms and social anxiety. A pathway involved in producing the short-chain fatty acid propionate was associated with poorer sleep quality.
Professor Kathrin Cohen Kadosh of the University of Surrey said the work moves beyond animal studies and offers human evidence that the microbiome’s neuroactive potential relates to the chemical balance of specific brain regions. Dr Nicola Johnstone of the University of Roehampton said the study connects microbial genes, brain neurochemistry and psychological measures in the same participants.
The authors stressed that the results show associations rather than cause and effect. They said the cross-sectional design cannot show whether microbiome differences influence brain chemistry, whether brain and behavioural factors influence the gut, or whether another biological process affects both. They also noted that the study measured genetic potential rather than directly measuring the metabolites produced by the bacteria.
Even so, the researchers said the findings narrow down microbial pathways that could be tested in future experiments. They added that larger longitudinal and intervention studies will be needed to determine whether changing these pathways can alter brain chemistry.
The study adds to growing interest in the gut-brain axis and may help guide future research into how microbial activity could shape mental health and cognition. For now, the work points to a more complex and region-specific relationship between gut bacteria and the brain than scientists had previously mapped.
Source article | Journal reference
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