The gut microbiome composition may play a key role in depression, findings from two international studies suggest.
Researchers in the Netherlands have identified a gut bacteria signature associated with the synthesis of neurotransmitters such as serotonin and gamma amino butyric acid (GABA), which are key mediators of mood and depression.
In a paper published in Nature Communications (link here), researchers from Erasmus Medical Center Rotterdam describe results from an investigation into the relation between faecal microbiome diversity and composition with depressive symptoms in 1,054 participants from the Rotterdam Study cohort.
They found 13 microbial taxa were significantly associated with higher depressive symptoms, including genera Eggerthella, Subdoligranulum, Coprococcus, Sellimonas, Lachnoclostridium, Hungatella, Ruminococcaceae (UCG002, UCG003 and UCG005), LachnospiraceaeUCG001, Eubacterium ventriosum and Ruminococcusgauvreauii group, and family Ruminococcaceae.
were. Some bacteria were more abundant in people with depression whereas others were depleted, the authors noted.
The associations were validated in a separate group of 1,539 individuals in the Amsterdam HELIUS cohort.
The study investigators said it was notable that most of the microbiota species linked to depression were involved in the synthesis of glutamate, butyrate, serotonin and GABA. Each of these neurotransmitters could alter brain chemistry – even when in peripheral tissues and therefore influence mood and behaviour via the gut-brain axis, the authors said
The findings therefore supported previous studies suggesting that gut microbiota may influence brain activity and behaviour via neural and humoral pathways, they concluded
In a separate study published in Nature Communications (link here), the same group of Dutch researchers identified a microbial signature predictive of depressive symptoms that was largely consistent across several ethnic groups.
Analysing data from the HELIUS cohort of 3211 individuals, they characterised the gut microbiota and its associations with depressive symptoms in six ethnic groups (Dutch, South-Asian Surinamese, African Surinamese, Ghanaian, Turkish, Moroccan), living in the same urban area.
As in the previous study they found that bacterial genera associated with depressive symptoms belonged to the families Christensenellaceae, Lachnospiraceae, and Ruminococcaceae.
The researchers also noted that diversity of the gut microbiota, both within and between individuals predicted depressive symptom levels, after taking into account demographic, behavioural, and medical differences.
The results therefore suggested that ethnic differences in depressive symptoms could be explained by at least partly explained by differences in microbiota composition.
“The study findings identified potential targets for psychobiotic interventions that warrant further investigation, and may positively impact depression and well-being at an individual or population level,” the authors said.
“Although the clinical impacts of these findings need to be confirmed experimentally, together the two studies further reinforce the link between gut microbiome composition and depression, and suggest it may be a useful target for future therapies,” the study investigators concluded.