Interruptions in gut microbiota during the early years of life can trigger the development of autism spectrum disorder and attention-deficit/hyperactivity disorder (ADHD), a new study reveals.

Latest research from the University of Florida and Linköping University in Sweden has established a connection between early gut microbiota disturbances and an increased risk of developing neurodevelopmental disorders.

Due to no clear biomarkers of the conditions showing during the initial stages of life, early detection has been challenging.

However, this finding could provide teams with a new approach to detect the conditions early and potentially prevent the disorders from forming fully.

Previous studies have found that autism and ADHD are caused by a range of genetic and environmental factors.

Up to two per cent of the global population are living with autism – a developmental disability caused by a difference in the brain.

People with autism often have problems with social communication and interaction, and restricted or repetitive behaviours or interests. They may also have different ways of learning, moving or paying attention.

Meanwhile, ADHD impacts up to seven per cent of children around the world and is one of the most prevalent childhood disorders.

ADHD is a condition that affects people’s behaviour, with symptoms including a short attention span, constantly fidgeting and acting without thinking.

Researchers have analysed the two-way communication pathway between the central nervous system and the gut microbiota to gain a better understanding of these two disorders.

Gut microbiota are the microorganisms that live in the digestive tracts of both humans and other animals.

The vagus nerve is included in the gut-brain axis – a nerve that extends from the brainstem to the abdomen, allowing the gut bacteria to communicate with the brain.

According to the research, gut microbiota can trigger the development of disorders like autism and ADHD because it can produce and respond to neurotransmitters and other chemicals that affect brain function, including short-chain fatty acids and inflammatory cytokines.

During the study, the team of scientists examined more than 16,000 children who were born in Sweden between October 1997 and October 1999. Each participant was analysed from birth right through to their early 20s.

The researchers took cord serum and stool samples of the participants when they were just one year old.

In addition, they looked at the participant’s family medical history, lifestyle factors, dietary habits and other environmental exposures.

They noticed a clear difference in the gut microbiota of young children who were later diagnosed with a neurodevelopment disorder.

The bacterial species Citrobacter was more common in infants who developed autism and ADHD, the study has reported.

Whereas the bacterial species Coprococcus was found to prevent the development of neurodevelopment disorders.

Additionally, the children with significantly lower levels of linolenic acid were likely to develop autism, the results have reported.

Those who went on to develop autism had higher levels of PFAS – potentially harmful chemicals that are ingested through water, food, and air.

Senior author Professor Eric W. Triplett said: “The remarkable aspect of the work is that these biomarkers are found at birth in cord blood or in the child’s stool at one year of age over a decade prior to the diagnosis.”

The bacterial strains Akkermansia muciniphila and Bifidobacterium were identified in lower abundances in children diagnosed with neurodevelopmental disorders.

Fellow author Angelica Ahrens said: “Coprococcus and Akkermansia muciniphila have potential protective effects. These bacteria were correlated with important substances in the stool, such as vitamin B and precursors to neurotransmitters which play vital roles orchestrating signalling in the brain.

“Overall, we saw deficits in these bacteria in children who later received a developmental neurological diagnosis.”

Johnny Ludvigsson, Senior Professor at the Department of Biomedical and Clinical Sciences at Linköping University, said: “We can see in the study that there are clear differences in the intestinal flora already during the first year of life between those who develop autism and ADHD and those who don’t.

“We’ve found associations with some factors that affect gut bacteria, such as antibiotic treatment during the child’s first year, which is linked to an increased risk of these diseases.”

The study was published in the journal Cell.

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