The Causal Relationships Between Gut Microbiota, Brain Volume, and Intelligence: A Two-Step Mendelian Randomization...

Area of Science:

• Neuroscience
• Microbiology
• Genetics

Background:

• Emerging evidence suggests a link between gut microbiome composition and cognitive abilities.
• The causal relationship between gut microbiota and intelligence remains unclear.

Purpose of the Study:

• To investigate the causal relationship between gut microbiota and intelligence using a Mendelian randomization approach.
• To explore potential mediation by brain volume in the microbiota-intelligence association.

Main Methods:

• A 2-sample Mendelian randomization (MR) analysis was conducted using large-scale genome-wide association studies data for gut microbiota and intelligence.
• Sensitivity analyses were performed to ensure the robustness of the findings.
• A 2-step MR analysis was employed to assess the mediating role of brain volume.

Main Results:

• A negative causal effect of the gut bacterium *Oxalobacter* on intelligence was identified (OR=0.968).
• A positive causal effect of the gut bacterium *Fusicatenibacter* on intelligence was observed (OR=1.053).
• The effect of *Fusicatenibacter* on intelligence was found to be partially mediated by brain volume (33.6%).

Conclusions:

• This study provides causal evidence for the influence of the gut microbiome on intelligence.
• The findings contribute to understanding the microbiota-gut-brain axis and may inform strategies for preventing cognitive impairment.