By Sarah Johnson
Autism Spectrum Disorder, or ASD, is a developmental disorder that causes social, communication, and behavior challenges. There is no evidence behind what causes ASD, as well as no cure for ASD. However, there are many different ideas and developing pieces of evidence to find the reasoning. One suspected idea is the gut microbiome of a person with ASD can be associated with the disorder. Researchers have also found that food and other types of allergies are more likely to be reported in children with ASD than those without autism (reasoning still unknown)1. That same research found that there is an association between those, food allergies are the most common allergy found in children with ASD1.
Knowing that children with ASD have a higher likelihood to have food allergies, researchers began to look at the gut health of children with ASD. Specifically, researchers look at the gut microbiome- which is bacteria, archaea, and fungi that live in the digestive tracts. These gut bacterias ( gut microbiome) directly stimulate neurons in the enteric nervous system to send signals to the brain. Gut microbes shape the architecture of sleep and stress reactivity of the hypothalamic-pituitary-adrenal axis2.
The growing information behind gut microbiome in social brain function influenced researchers from Arizona State University to run a study on the role of gut microbes in ASD. In the study they recruited 18 children with ASD ages 7 to 16, that had a history of gastrointestinal problems, including chronic diarrhea, pain, and constipation.
The children apart of the study were given an antibiotic called vancomycin for two weeks to remove existing bacteria. Then, each of them received a high dose of gut microbes from donors without autism. The children took a daily dose of the microbes for seven/eight weeks as well as an antacid to neutralize stomach acid- helping to improve the chance of the new microbes surviving.
The research concluded at the end of the 18-week study period, the children’s gastrointestinal symptoms had reduced by 80%, and most of the improvement remained two years after the original study3.
Continuing into two years after the study, the children’s scores on a test to measure how much they were affected by their autism were an average of 47% lower than they had been at the beginning of the trial.
It was also found at the two-year update the children had increased gut-bacterial diversity and greater numbers of gut bacteria that are often found in lower numbers in children with ASD (such as Bifidobacteria and Prevotella). Krajmalnik-Brown, a researcher in the study, said that this suggests the treatment had succeeded in changing their microbiomes long term3. For more information on this research please watch their youtube video explaining the resultsThe Gut Microbiome: Opening new possibilities for autism treatment.
Since there is an association between gut microbiome and children with ASD, we must now look at the role that genetics and parenthood play. Since research on the gut microbiome and ASD is very little, so is the research on the gut microbiome of a mother with a child who has ASD. Nonetheless, what researchers have found points to an association of the gut microbiome in a mother being associated with ASD.
A clinical study showed that the gut microbial alterations in ASD children were consistent with those in their mothers, suggesting that alterations in maternal gut microbiota are related to the increased risk of ASD in children4.
The maternal gut microbiota influences offspring gut microbial structure and composition. However, the relationship between the clinical symptoms of autism spectrum disorder and the gut bacteria shared between children and their mothers is unknown4.
Other studies have suggested that inflammation-induced maternal immune activation, prenatal exposure to immune challenges, and maternal obesity, stress, and gastrointestinal symptoms during pregnancy play roles in perinatal neurodevelopmental brain damage and contribute to an increased risk of subsequent neuropsychiatric disorders, such as ASDs5. There is also biological evidence that prenatal factors trigger a more active immune state in the mother, which is associated with the development of autism5.
As stated before, there is no cure or reasoning behind autism spectrum disorder. All of the research mentioned are associations, not causations. This means that food allergies do not cause autism, the same way autism does not cause food allergies. All of the evidence just concludes that there are associations. As time goes on, so will developments in research behind autism spectrum disorder. To learn more about ASD please see our other blog posts.
1 Xu G, Snetselaar LG, Jing J, Liu B, Strathearn L, Bao W. Association of Food Allergy and Other Allergic Conditions With Autism Spectrum Disorder in Children. JAMA Netw Open. 2018;1(2):e180279. doi:10.1001/jamanetworkopen.2018.0279
2 Galland L. The gut microbiome and the brain. J Med Food. 2014 Dec;17(12):1261-72. doi: 10.1089/jmf.2014.7000. PMID: 25402818; PMCID: PMC4259177.
3Kang, DW., Adams, J.B., Coleman, D. et al. Long-term benefit of Microbiota Transfer Therapy on autism symptoms and gut microbiota. Sci Rep 9, 5821 (2019). https://doi.org/10.1038/s41598-019-42183-0
4 Chen, Yu et al. “Gut Bacteria Shared by Children and Their Mothers Associate with Developmental Level and Social Deficits in Autism Spectrum Disorder.” mSphere vol. 5,6 e01044-20. 2 Dec. 2020, doi:10.1128/mSphere.01044-20
5 Patterson, Paul H. "Maternal infection and immune involvement in autism." Trends in molecular medicine 17.7 (2011): 389-394.