Two genetic analyses to elucidate causality between body mass index and personality

Area of Science:

• Behavioral genetics
• Psychology
• Public health

Background:

• Correlations exist between personality traits and body mass index (BMI), but causal links are not well understood.
• Clarifying the direction of causality is crucial for informing weight management strategies and understanding personality development.

Purpose of the Study:

• To investigate the existence and direction of causal relationships between BMI and personality traits.
• To determine if personality influences BMI or if BMI influences personality.

Main Methods:

• Employed Mendelian randomization using allele scores for personality traits (neuroticism, worry, depressive affect) to predict BMI.
• Utilized an allele score for BMI to predict phenotypic personality scores (PPSs).
• Conducted a direction of causation (DoC) analysis on twin data to compare models of BMI influencing personality, personality influencing BMI, reciprocal causation, and no causation.

Main Results:

• Mendelian randomization indicated that an allele score for BMI predicted domain-general and eating-specific PPSs.
• An allele score for worry predicted BMI, but scores for neuroticism and depressive affect did not.
• DoC analysis revealed that BMI causally influences domain-general and eating-specific personality traits.

Conclusions:

• Genetic analyses suggest a primary causal influence of BMI on personality traits.
• The influence of personality traits on BMI appears to be weaker.
• Reciprocal causation may exist for domain-general personality traits in individuals with higher BMI (BMI > ~25).