A study found that microorganisms (microbiome) living in the gut during childhood may influence the later risk of developing emotional problems such as anxiety and depression.
Researchers at the University of California, Los Angeles (UCLA) Center for Health Sciences said there is a meaningful association among the composition of gut bacteria in infancy, brain neural networks related to emotion in the early elementary school years, and anxiety and depressive symptoms. The study was published on the 30th in the international journal "Nature Communications."
According to the study, the more bacteria belonging to the Clostridiales order and the Lachnospiraceae family in the gut of a child around age 2, the higher the likelihood of showing anxiety or depressive symptoms around the time of entering elementary school (age 7). The two bacterial groups are also known from adult studies to be related to stress responses and depression.
The researchers explained this process as the so-called "gut-brain axis," meaning the gut and brain communicate with each other through microbes. They noted that gut bacteria influence the brain's emotion-processing network, which is then reflected in mental health over time. It has previously been shown that gut microbes are not involved only in digestion but also affect emotions and stress responses.
The study used data from the "Growing Up in Singapore Towards healthy Outcomes (GUSTO)" project in Singapore. The researchers analyzed gut microbes by collecting credit entry samples from 55 children at age 2 and, at age 6, checked the consolidation of emotion-related brain networks with magnetic resonance imaging (MRI). Then, at age 7 and a half, they assessed the children's tendencies toward anxiety or depression through a survey of their guardians.
Bridget Callaghan, a UCLA psychology professor who led the study, said, "We present early evidence that gut microbes in early childhood can influence the formation of mental health during the school years," adding, "If these results are shown to be causal, even simple approaches such as diet or probiotic (beneficial bacteria) supplementation could open a path to protecting children's mental health."
However, this is an observational study and does not prove a causal relationship that bacteria actually affected mental health. The researchers added that with further research, they plan to determine how specific bacteria influence brain development and what methods could modulate this.
Callaghan said, "It is now important to identify which bacteria specifically have an impact," adding, "Once we know this, it may be possible to prevent anxiety or depression by changing the gut environment."
References
Nature Communications (2025), DOI: https://doi.org/10.1038/s41467-025-64988-6