Children who face adversities -- such as parental separation -- are more likely to suffer from gastrointestinal symptoms which may lead to mental health issues in later life, a study has found.
The study, published in the journal Development and Psychopathology, found that gastrointestinal symptoms in children may have an impact on the brain and behaviour as they grow to maturity.
"One common reason children show up at doctors' offices is intestinal complaints," said Nim Tottenham, a professor at Columbia University in the US.
"Our findings indicate that gastrointestinal symptoms in young children could be a red flag to primary care physicians for future emotional health problems," said Tottenham.
Scientists have long noted the strong connection between the gut and brain. Previous research has demonstrated that a history of trauma or abuse has been reported in up to half of adults with irritable bowel syndrome (IBS), at a prevalence twice that of patients without IBS.
"The role of trauma in increasing vulnerability to both gastrointestinal and mental health symptoms is well established in adults but rarely studied in childhood," said Bridget Callaghan, a post-doctoral research fellow at Columbia.
Animal studies have demonstrated that adversity-induced changes in the gut microbiome -- the community of bacteria in the body that regulates everything from digestion to immune system function -- influence neurological development, but no human studies have done so.
"Our study is among the first to link disruption of a child's gastrointestinal microbiome triggered by early-life adversity with brain activity in regions associated with emotional health," Callaghan said.
The researchers focused on development in children who experienced extreme psychosocial deprivation due to institutional care before international adoption.
Separation of a child from a parent is known to be a powerful predictor of mental health issues in humans.
That experience, when modelled in rodents, induces fear and anxiety, hinders neurodevelopment and alters microbial communities across the lifespan.
The researchers drew upon data from 115 children adopted from orphanages or foster care on or before approximately they were two years old, and from 229 children raised by a biological caregiver.
The children with past caregiving disruptions showed higher levels of symptoms that included stomach aches, constipation, vomiting and nausea.
From that sample of adoptees, the researchers then selected eight participants, ages seven to 13, from the adversity exposed group and another eight who'd been in the group raised by their biological parents.
Researchers collected behavioural information, stool samples and brain images from all the children. They used gene sequencing to identify the microbes present in the stool samples and examined the abundance and diversity of bacteria in each participant's faecal matter.
The children with a history of early caregiving disruptions had distinctly different gut microbiomes from those raised with biological caregivers from birth.
Brain scans of all the children also showed that brain activity patterns were correlated with certain bacteria.
For example, the children raised by parents had increased gut microbiome diversity, which is linked to the prefrontal cortex, a region of the brain known to help regulate emotions.
"It is too early to say anything conclusive, but our study indicates that adversity-associated changes in the gut microbiome are related to brain function, including differences in the regions of the brain associated with emotional processing," said Tottenham.
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