The causal relationships between limb fat distribution and mental disorders: A Mendelian randomization study

Area of Science:

• Genetics
• Psychiatry
• Metabolic Health

Background:

• Understanding the interplay between body composition and mental health is crucial for developing comprehensive treatment strategies.
• Previous research suggests potential links between metabolic factors and psychiatric disorders, but causal relationships remain underexplored.

Purpose of the Study:

• To investigate the potential causal effects of limb fat distribution on four major mental disorders using a robust genetic approach.
• To determine if specific patterns of fat mass in the arms and legs are associated with increased risk for attention-deficit/hyperactivity disorder (ADHD), major depressive disorder (MDD), schizophrenia, and bipolar disorder.

Main Methods:

• A two-sample Mendelian randomization (MR) analysis was conducted using summary statistics from large-scale genome-wide association studies (GWAS) in a European population.
• Inverse variance weighting (IVW) was the primary analysis method, with sensitivity analyses including MR-Egger, weighted median, and mode-based methods to ensure result validity.

Main Results:

• Significant causal relationships were identified between limb fat mass and both attention-deficit/hyperactivity disorder (ADHD) and major depressive disorder (MDD).
• Specifically, higher right arm and left leg fat mass showed a negative correlation with ADHD and MDD, while higher left arm and right leg fat mass showed a positive correlation.
• No significant causal associations were found for schizophrenia or bipolar disorder.

Conclusions:

• Limb fat distribution appears to have a causal influence on the risk of developing attention-deficit/hyperactivity disorder (ADHD) and major depressive disorder (MDD).
• These findings highlight the complex relationship between body composition and mental health, suggesting potential targets for intervention and prevention strategies.