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A study conducted in Taiwan found that autistic individuals tend to show differences in gut microbiota composition compared to both non-autistic individuals and their siblings without autism. More specifically, the autistic group showed distinct differences in the beta diversity of their gut microbiota. Individuals with more Anaerostipes bacteria exhibited significantly less social impairment and internalizing problems. The paper was published in Translational Psychiatry.
The gut microbiota is the complex community of microorganisms, mainly bacteria, that live in the human gastrointestinal tract. These microorganisms play a crucial role in digestion, metabolism, immune function, and protection against pathogens.
They also communicate with the central nervous system through a bidirectional communication pathway called the microbiota-gut-brain axis. Signals between the brain and the gut microbiota travel via multiple physiological paths, including the vagus nerve, immune system biochemicals, and microbial metabolites such as short-chain fatty acids.
Research shows that, through the microbiota-gut-brain axis, gut microbiota can influence brain development, stress reactivity, and emotional regulation. Differences in gut microbiota composition have been associated with psychological characteristics such as anxiety, depression, stress sensitivity, and cognitive functioning.
Experimental studies suggest that altering the gut microbiota through diet, probiotics, or antibiotics can lead to changes in mood and behavior. Early-life microbiota development appears particularly important for later psychological outcomes.
Study author Jung-Chi Chang and his colleagues wanted to investigate the associations between gut microbiota composition and autism features. They also wanted to compare microbial profiles between autistic individuals, their non-autistic siblings, and unrelated non-autistic individuals. The study authors hypothesized that gut microbiota diversity would differ between these three groups and that the gut microbiota composition of autistic individuals and their siblings would show unique features compared to non-autistic individuals.
The study included 239 autistic individuals, 102 non-autistic biological siblings of these individuals, and 81 unrelated non-autistic children and young adults from Taiwan. The average age of the autistic participants and their siblings was approximately 12 years, while the average age of the unrelated non-autistic participants was approximately 14. In general, participants’ ages ranged between 4 and 25 years.
Autistic participants were required to have a clinical diagnosis of autism. This diagnosis was confirmed through interviews conducted by the authors (using the Autism Diagnostic Interview-Revised and the Autism Diagnostic Observation Schedule). Non-autistic participants were required to have no diagnosis of psychiatric disorders or neurological or systemic medical conditions.
The study authors obtained information about participants’ autism-related behaviors and emotional and behavioral issues from their caregivers (using the Social Responsiveness Scale and the Child Behavior Checklist). Study participants provided fecal samples, allowing the authors to analyze the composition of their gut microbiota. Participants and their parents also reported any gastrointestinal symptoms the participants had experienced in the past 4 weeks.
Results showed that, compared to unrelated non-autistic participants, siblings of autistic individuals had higher alpha diversity, while autistic participants had a different beta diversity in their gut microbiota.
Alpha diversity of gut microbiota refers to the diversity of microbial species within a single individual or sample, reflecting the richness and evenness of the community. Beta diversity of gut microbiota reflects differences in microbial composition between individuals or samples, indicating how distinct their microbial communities are from one another.
Unrelated non-autistic participants had a higher relative abundance of Blautia, Eubacterium hallii group, Anaerostipes, Erysipelotrichaceae UCG 003, Parasutterella, and Ruminococcaceae UCG 013 at the genus level compared to autistic participants and their siblings. The family Prevotellaceae and genera Agathobacter microbes were more abundant in siblings of autistic participants compared to both autistic participants and unrelated non-autistic participants. Individuals with more Anaerostipes bacteria tended to have significantly less social impairment and internalizing problems.
“Our study reveals unique microbial compositions in the ASD [autism spectrum disorder] and SIB [siblings] groups and a relationship between behavior patterns and microbial composition. These findings suggest the potential of microbial interventions for autistic individuals that warrant further exploration,” the study authors concluded.
The study contributes to the scientific understanding of the links between gut microbiota composition and psychological processes and characteristics. However, it should be noted that the cross-sectional design of this study does not allow for causal inferences to be derived from the results.
The paper, “Identifying gut microbiota composition disparities in autistic individuals and their unaffected siblings: correlations with clinical characteristics,” was authored by Jung-Chi Chang, Yu-Chieh Chen, Hai-Ti Lin, Yan-Lin Chen, and Susan Shur-Fen Gau.