results . These limitations raise an important question : Does the microbiome play a direct role in the development of autism and other neurodevelopmental conditions , or are changes in microbiome composition a consequence of the conditions themselves ?
Some investigations have proposed that the microbiome has little or no association with future autism . However , these studies have a notable limitation : They don ’ t examine microbial imbalances prior to diagnosis or symptom onset . Instead , these studies focus on children already diagnosed with autism , comparing them to their siblings and unrelated neurotypical children . In most cases , dietary data and samples are collected several years after diagnosis , meaning the study cannot test for whether microbial imbalances cause autism .
Microbes matter
We wondered whether studying the bacteria residing in small children before they are diagnosed or show symptoms of autism or other conditions could give us a clue into their neurodevelopment . So , we examined the cord blood and stool collected at approximately 1 year of age from participants of an ongoing study called All Babies in Southeast Sweden , which follows the health of approximately 17,000 children born between 1997 and 1999 and their parents . We have followed these children since birth , nearly 1,200 of whom were later diagnosed with a neurodevelopmental disorder by age 23 . crankiness and sleep problems – as well as formal medical diagnoses . These differences spanned many conditions , including autism , ADHD and speech disorders .
Next , we linked bacteria to neurotransmitters – chemical signals that help brain cells communicate – and vitamins such as riboflavin and vitamin B in the child ’ s stool . Given previous research on children and adults already diagnosed with a neurodevelopmental disorder , we expected to find differences in the microbiome composition and health between those with and without neurodevelopmental conditions .
But we were surprised to discover just how early these differences emerge . We saw variability in the microbes and metabolites that affect immune and brain health , among others , in the stool collected from the diapers of children around 1 year of age and in umbilical cord blood collected at birth .
The imbalance in microbial composition – what microbiologists call dysbiosis – we observed suggests that incomplete recovery from repeated antibiotic use may greatly affect children during this vulnerable period . Similarly , we saw that repeated ear infections were linked to a twofold increased likelihood of developing autism .
Children who both repeatedly used antibiotics and had microbial imbalances were significantly more likely to develop autism . More specifically , children with an absence of Coprococcus comes , a bacterium linked to mental health and quality of life , and increased prevalence of Citrobacter , a bacterium known for antimicrobial resistance , along with repeated antibiotic use were two to four times more likely to develop a neurodevelopmental disorder .
Antibiotics are necessary for treating certain bacterial infections in children , and we emphasize that our findings do not suggest avoiding their use altogether .
We found significant differences in bacterial composition and metabolite levels that developed before symptoms of neurodevelopmental conditions – such as gastrointestinal upset ,
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The researchers identified a link between imbalance of Akkermansia muciniphila and later development of neurodevelopmental disorders . Zhang et al . 2019 / Microbial Biotechnology , CC BY-SA
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