Potential similarities in gut microbiota composition between autism spectrum disorder and neurotypical siblings: Insights from a comprehensive meta-analysis.

Researchers compared gut bacteria in autistic children with their non-autistic siblings to see if there are meaningful differences. They found that autistic children's gut bacteria were very similar to their siblings', with only small, inconsistent differences in 3 types of bacteria. This suggests that gut bacteria differences in autism may not be as significant as previously thought, or that other factors are involved.

This meta-analysis examined gut microbiota composition in 248 individuals with autism spectrum disorder compared to 197 neurotypical siblings across 8 studies. By comparing with siblings who share similar genetics and living environments, researchers aimed to better control for confounding factors like diet and lifestyle that typically influence gut bacteria studies. Results showed significant but unstable differences in only 3 bacterial groups (Bacteroidetes, Firmicutes, and Fusobacteria), while 9 other bacterial groups showed no significant differences. The findings suggest gut microbiota composition in autistic individuals closely resembles that of their neurotypical siblings, indicating other factors or bacterial interactions may be more important in autism-related gut microbiome differences.

Results suggest gut microbiome interventions targeting general bacterial composition may have limited effectiveness in autism. Focus should shift to identifying specific bacterial interactions, environmental factors, or other mechanisms that influence autism-related gut differences.

Only 8 studies included with relatively small sample sizes. Differences found were described as 'unstable,' indicating inconsistent results across studies. Limited to specific bacterial groups and may not capture broader microbiome complexity or interactions.

Previous studies have explored the differences in gut microbiota (GM) between individuals with autism spectrum disorder (ASD) and neurotypical controls. However, factors such as diet, lifestyle, and environmental exposure influence GM, leading to significant variability, even among neurotypical individuals. Comparing the GM of ASD individuals with neurotypical siblings, who share similar genes and living conditions, may offer better insights into the GM mechanisms associated with ASD. Therefore, this study aims to analyze the GM composition in ASD by comparing it to that of neurotypical siblings, potentially identifying microbiota that influence ASD.

We explored electronic databases up to July 2024, including EBSCOhost, PubMed, ScienceDirect, Web of Science, and Scopus. Meta-analysis using RevMan 5.4 assessed the relative abundance (RA) of gut bacteria from 8 phyla and 4 genera in ASD individuals and neurotypical siblings. Eight studies were included, involving 248 people with ASD and 197 neurotypical siblings. Significant but unstable differences were observed in the RA of Bacteroidetes, Firmicutes, and Fusobacteria.

No significant differences were found in the RA of Proteobacteria, Cyanobacteria, Actinobacteria, Verrucomicrobia, Tenericutes, or Bacteroides, Roseburia, Sutterella, Bifidobacterium. GM composition in ASD individuals closely resembles that of neurotypical siblings, with only a few unstable differences. This suggests that other crucial bacteria or certain interacting environmental factors play a role. Further studies are needed to gather stronger evidence to uncover the differences in GM and their mechanisms in ASD people.