Autism and the Oral Microbiome: A Systematic Review of Host-microbial Interactions and Diversity
Bibliographic record
Abstract
BACKGROUND: Emerging evidence suggests a link between the oral microbiome and autism spectrum disorder (ASD), a neurodevelopmental condition characterised by social and behavioural impairments. The vast microbial reservoirs in the gut complement those of the oral cavity, suggesting a potential oral-gut-brain axis that may influence ASD and perhaps other neurological diseases, such as Parkinson's syndrome and Alzheimer's disease. For the first time, this systematic review synthesises the current knowledge of oral microbiome composition, diversity, and functionality in ASD and its potential diagnostic and therapeutic implications. METHODS: A comprehensive literature search was conducted using Medline (PubMed), Embase, Scopus, and Google Scholar for peer-reviewed case-control and cross-sectional studies published between January 2000 and January 2025. Study quality was assessed using the Newcastle-Ottawa scale. RESULTS: Nine studies (n = 8533; 2536 ASD and 5937 controls) met the inclusion criteria. The overall findings on microbial diversity were inconsistent; some studies reported alterations in ASD, while others found no significant differences. Functional profiling revealed enrichment of pathways involved in dopamine and GABA degradation, as well as disruptions in lysine metabolism, suggesting possible links to neurotransmitter imbalances in ASD. Although external factors such as selective eating, oral hygiene, and cognitive function were proposed to influence microbial profiles, statistical evidence supporting these associations was lacking. Moreover, no consistent link was found between oral microbiota features and core ASD symptoms like repetitive behaviours or communication deficits. CONCLUSION: This review highlights subtle yet potentially significant alterations in the oral microbiome of individuals with ASD, particularly in metabolic pathways that affect neurotransmitters. While direct associations with clinical symptoms remain unsubstantiated, the findings emphasise the importance of future multi-omics and longitudinal studies to clarify the oral microbiome's role in ASD pathophysiology and to explore its potential in personalised therapeutic strategies.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.025 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.006 | 0.006 |
| Bibliometrics | 0.015 | 0.013 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".