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

Background: 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. Methods: 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. Results: 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. Conclusions: 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.