In autism, there is a significant number of children that struggle with gastrointestinal symptoms, such as classic irritable bowel disease, esophagitis, and chronic duodenitis. Many investigators assume that these abnormalities and others are due to microbial dysbiosis, which includes inappropriate concentrations of Candida albicans and clostridia bacteria. These associations between behavior and gastrointestinal symptoms have often been described as the gut-brain axis. Small intestinal bacterial overgrowth (SIBO) can contribute to malabsorption of essential nutrients and gastrointestinal permeability (leaky-gut), which represents the basic concept of the gut-brain hypothesis. Nutrients are the building blocks for critical cellular functioning and significantly impacts brain health. Further, when the gastrointestinal tract leaks microbes (viral agents) and other particles this increases the odds that those substances will find their way into the bloodstream and brain.
The authors from Cangzhou Central Hospital in Beijing, China developed a large, prospective population-based case-controlled study to assess the prevalence of SIBO in autism. During the years 2011 to 2013, the investigators identified 310 children, which were diagnostically confirmed as having autism through the Autism Diagnostic Interview-Revised (ADI-R) and DSM-5 standards. The control group was sex and aged matched with a ratio of four controls to one autism participant. Further, the control group was clinically examined to ensure they did not have an autism diagnosis. The study documented autism severity by using the Autism Treatment Evaluation Checklist (ATEC) instrument, which was critical when analyzing the relationship between autism and SIBO. The analysis of SIBO among the study participants was conducted with the hydrogen and methane breath test. The initial test was collected in the morning after 12 hours of fasting. Six consecutive breath tests were obtained based on timing and after ingestion of glucose. The analysis of these samples was blindly evaluated at an independent laboratory.
The results of this study found a significant association between SIBO in the autism population when compared to the control group (31% vs. 9.3%, P < 0.001). Further, utilizing the breath test data in comparison with ATEC scoring it was observed that patients with SIBO were considered more severe on the autistic spectrum. This could lead to conclusions that SIBO may exacerbate or be causal in some cases of autism. Future studies should investigate regressive autism and SIBO, which was not captured in this study due to the participant’s age range. Clinical treatment protocols of SIBO should be developed to evaluate symptom improvement with prescribed medical care.
This study strengthens the association of microbial dysbiosis in children diagnosed with autism. Further, the large sample size and prospective methodology make the weight of the author’s conclusions hard to ignore.
Wang, L., Yu, Y., Zhang, Y., Zhang, J., Lu, N., & Liu, N. (2018). Hydrogen breath test to detect small intestinal bacterial overgrowth: a prevalence case-control study in autism. European Child Adolescence Psychiatry. https://doi.org/10.1007/s00787-017-1039-2