Exploring Gut-Brain Axis Mechanisms in Autism and ADHD: Shared and Distinct Pathways

October 11, 2026 2 Min Read

Introduction

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are common neurodevelopmental conditions with complex and not fully understood biological origins. Recent research has focused on the gut-brain axis (GBA), a communication network linking the intestinal microbiome with brain function through hormonal, immune, neural, and metabolic pathways. This axis may help explain how environmental factors interact with genetics to influence neurodevelopment.

Study Overview

A recent scoping review systematically examined peer-reviewed studies published between 2018 and early 2025 to map evidence on gut microbiome-related mechanisms in ASD and ADHD. The review included 45 studies investigating gut microbiome composition, signaling through the GBA, and microbiome-targeted interventions. Data were analyzed thematically to identify common and disorder-specific pathways.

Key Mechanistic Themes Identified

The analysis revealed five main mechanistic themes:

Endocrine dysregulation and microbial metabolite signaling
Neuronal signaling and neurotransmitter modulation
Immune activation and neuroinflammation
Gene-microbiota-environment interactions
Microbiota-targeted interventions

Shared Features Between ASD and ADHD

Both disorders showed alterations in gut bacteria capable of producing short-chain fatty acids (SCFAs), important microbial metabolites involved in gut and brain health. However, findings were inconsistent, and there was no clear evidence of a uniform decrease in butyrate, a key SCFA.

Distinctive Findings in ASD

ASD was characterized by notable disruptions in the serotonergic system and the tryptophan-kynurenine metabolic pathway. Additionally, individuals with ASD exhibited heightened responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis, which regulates stress hormones.

Distinctive Findings in ADHD

Research on ADHD remains preliminary, mostly cross-sectional, and has yet to link the well-established dopaminergic dysfunction in ADHD to specific gut microbiome changes. The evidence base for microbiome mechanisms in ADHD is therefore less developed compared to ASD.

Implications for Families and Future Research

This review underscores the potential of the gut-brain axis framework to deepen understanding of ASD and ADHD. However, translating these insights into clinical interventions will require longitudinal studies employing multi-omic approaches to clarify causal relationships and enable personalized microbiome-based treatments.

Limitations and Cautions

Current evidence is varied and often preliminary, especially regarding ADHD. The complexity of microbiome interactions and neurodevelopmental disorders means that findings should be interpreted cautiously. More rigorous, well-designed research is essential before microbiome-targeted therapies can be recommended.

For detailed study information, see the original publication: Gut microbiota and the gut-brain axis in autism spectrum disorder and attention-deficit/hyperactivity disorder: A scoping review.