Paper Suggests Link Between Gut Biome and ADHD, Autism

by Denis Storey
April 23, 2024 at 11:32 AM UTC

Researchers discovered a connection between ADHD and autism and disruptions in the gut biome during early childhood.

Clinical relevance: Researchers from the University of Florida and Swedish universities found a link between ADHD, autism, and disruptions in early childhood gut flora.

  • Leveraging 20 years of data from more than 16,000 Swedish children, they analyzed umbilical cord blood and stool samples to identify early risk factors.
  • Children with neurodevelopmental disorders lacked certain gut-health-promoting bacteria, linked to factors like antibiotics for ear infections.
  • The study also implicated environmental factors – such as parental smoking and childhood stress – highlighting the impact on the microbiome.

Researchers half a world apart shared a gut feeling about attention-deficit attention disorder (ADHD) and autism. And it appeared to bear fruit. Scientists at the University of Florida and a pair of Swedish schools oversaw research that has uncovered a connection between those neurodevelopmental disorders and the gut biome.

The teams found that agitated gut flora during the first few years of a child’s life might have some bearing on the development of ADHD and autism. The groundbreaking study suggests that gut biome fluctuations influenced later diagnoses of these disorders. The authors found links between environmental factors and common childhood ear infection treatments.

Methodology

Researchers from UF’s Institute of Food and Agricultural Sciences – along with Linköping University and Örebo University in Sweden – oversaw the study by leveraging 20 years of data collected from more than 16,000 Swedish children who were part of the All Babies in Southeast Sweden (ABIS) cohort.

Nearly 1,200 of them – or 7.28 – went on to develop a neurodevelopmental disorder.

The research teams looked at data from the first five years of life, focusing on biological and environmental factors that might affect certain bacteria linked to nervous system development. Specifically, the scientists pored over umbilical cord blood taken from the children at birth and stool samples collected a year later to compare the children’s microbiomes and isolate the earliest risk factors for future neurodevelopmental disorders.

The children’s parents supplemented the research with questionnaires designed to establish cognitive function, social behavior, and environment.

The research teams found obvious differences in infant gut microbiomes who eventually received neurodevelopmental diagnoses. These varied, but some common threads appeared.

Infants who developed neurodevelopmental disorders lacked certain gut-health-promoting bacteria, such as Akkermansia, Bifidobacterium, Ruminococcus, and Faecalibacterium. The link remained strong, despite controls for other factors, whether it was diet, psychosocial vulnerability, and toxic exposures.

“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 or ADHD and those who don’t,” Johnny Ludvigsson, senior professor at the Department of Biomedical and Clinical Sciences at Linköping University, who co-led the study, said. “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.”

Other Gut Biome Surprises

That connection to antibiotics used to treat early childhood ear infections, like penicillin, surprised the researchers

“We’re not trying to say that antibiotics are necessarily a bad thing,” Angelica Ahrens, a UF/IFAS assistant research scientist and the study’s lead author, added. “But perhaps overuse can be detrimental to the microbiome, and for some children, for whatever reason, their microbiome might not recover as readily.”

The teams found that children who experienced three or more ear infections requiring penicillin between birth and age 5 were:

  • Nearly four times more likely to develop a speech disorder.
  • 3.27 times more likely to develop ADHD.
  • And 2.44 times more likely to develop an intellectual disability.

Additionally, kids who suffered ear infections three or more times between the ages of 1 and 2.5 years old were:

  • 1.74 times more likely to develop autism.
  • 1.75 times more likely to develop ADHD.
  • And 2.13 times more likely to be diagnosed with an intellectual disability.

But What Drives the Connection?

The answer might be in the stool samples.

Compared to children without multiple ear infections, the microbiomes of those who did develop neurodevelopmental disorders years later featured elevated levels of Citrobacter, a type of bacteria linked with inflammation, and lower levels of Coprococcus, tied to positive mental health.

The researchers theorize that penicillin boosts Citrobacter and inhibits the growth of Coprococcus.

The researchers blame some environmental exposure, such as parents who smoked and childhood stress. The study shows that maternal smoking during pregnancy made the children three times to develop a neurodevelopmental disorder. With heavier smokers – mothers who smoked more than 15 cigarettes a day – that secondhand smoke caused their toddlers to become 4.88 times more likely to develop ADHD. And when fathers smoked more than 15 cigarettes a day, the kids were 3.47 times more likely to develop autism.

“There’s a pretty consistent pattern where it seems increased stressors – whether from emotional stress or exposure to adverse health influences – can impact the immune system and, subsequently, the microbiome – along with all its downstream effects,” Ahrens said.

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