The Gut Microbiome, ADHD and Autism: Emerging Evidence and Clinical Perspectives

Growing research interest in the gut–brain axis has led to increasing exploration of how the gut microbiome may influence neurodevelopmental conditions, including Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). While this remains an evolving area of science, emerging evidence suggests that gut microbiome composition may be associated with certain neurological and behavioural features, prompting further investigation into microbiome based adjunctive approaches within a broader clinical framework.

The Gut Microbiome and Neurodevelopmental Health

At OT&P, we have been using the GI‑MAP® advanced stool microbiome test since it first became commercially available over 10 years ago. Over time, both the test itself and our clinical understanding of how to interpret and respond to microbiome findings have continued to evolve.

Historically, this form of testing has been used primarily in the assessment of Irritable Bowel Syndrome (IBS) and other gastrointestinal conditions. In recent years, microbiome testing has also been explored as an adjunctive tool to support the broader clinical understanding of children with developmental and neurodevelopmental conditions, including Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD).

I was recently present at the launch of the MetaGenie test, developed by The Chinese University of Hong Kong (CUHK) and MicrosigX. This test has been developed to support research and risk stratification relating to gut microbiome patterns that may be associated with autism, rather than as a diagnostic tool.

Gut Microbiome‑Targeted Interventions in ADHD and Autism

Further supporting interest in this area, a recent peer‑reviewed article entitled “Efficacy of gut microbiota‑based therapy for Autism Spectrum Disorder and Attention Deficit Hyperactivity Disorder” examined the potential role of microbiome‑targeted interventions in neurodevelopmental conditions.

The authors concluded that gut microbiome‑based therapies demonstrate a small but measurable overall benefit for certain neurodevelopmental symptoms, with more consistent and clearer effects observed in ADHD compared to ASD.

Overview of the Research

The study sought to evaluate the effectiveness of gut microbiota‑targeted interventions, including:

Probiotics
Prebiotics
Dietary modifications
Faecal microbiota transplantation (FMT)

These interventions were assessed in relation to symptom severity and associated features in individuals with ADHD and ASD.

A systematic review and meta‑analysis was conducted, screening major medical databases up to August 2024, with inclusion limited to randomised controlled trials. Interventions were compared with placebo or usual care.

Key Findings: Differential Effects in ADHD and ASD

The analysis identified a small but statistically significant improvement in core neurodevelopmental or related symptoms across all microbiota‑based interventions combined.

In ADHD, trials demonstrated a larger and statistically significant improvement, consistent with a small‑to‑moderate effect size.
In ASD, the observed effect was very small and not statistically significant, suggesting that current microbiome‑based interventions show uncertain benefit for core autism symptoms.

These findings highlight potential differences in how gut‑focused interventions may influence ADHD and ASD.

Safety and Tolerability

Across the included studies, acceptability and safety outcomes were comparable between intervention and control groups. Drop‑out rates did not differ meaningfully, indicating that microbiota‑based interventions were generally well tolerated in both ADHD and ASD study populations.

Clinical Considerations

While interest in the gut–brain axis continues to grow, microbiome‑based therapies should be considered adjunctive approaches rather than primary or standalone treatments. Diagnosis and management of ADHD and ASD should remain grounded in established clinical frameworks, with microbiome findings interpreted within the context of a comprehensive medical and developmental assessment.

Ongoing research and advances in microbiome science may further clarify the role of these interventions in the future.