ASD Colorado Longitudinal

Research relating gut microbiome composition to autism spectrum disorders (ASD) has produced inconsistent results, indicative of the disorder's complexity and the need for more sophisticated experimental designs. We address this need by 1) comparing gut microbiome composition between individuals with ASD and neurotypical controls in Arizona and Colorado using standardized DNA extraction and sequencing methods at both locations, and 2) longitudinally evaluating the gut microbiome's relationship to autism behavioral severity, diet, and gastrointestinal symptoms. Gut microbiome composition differed between individuals in Arizona and Colorado and gastrointestinal symptoms were significantly higher in ASD compared to neurotypical in Arizona, but not Colorado. Gut microbiome composition significantly associated with ASD while controlling for study-site location, but not when controlling for gastrointestinal symptoms, suggesting that non-ASD related study-site differences in gut microbiome composition and different degrees of gastrointestinal symptoms involvement with ASD between sites may contribute to inconsistent results in the literature regarding the association between gut microbiome composition and ASD. In the longitudinal analysis, we found that difference in levels of lethargy/social withdrawal measured in individuals at different time points correlated with the degree of change in gut microbiome composition and that a worsening of inappropriate speech between time points was associated with decreased gut microbiome diversity. This relationship between changes in the gut microbiome composition within individuals and ASD behavioral severity metrics, indicates that longitudinal study designs may be a useful way to explore microbial drivers of ASD severity when substantial variability exists in baseline microbiome compositions across individuals and geographical regions.