Body mass index and psychiatric disorders: a Mendelian randomization study

Area of Science:

• Genetics
• Psychiatry
• Epidemiology

Background:

• Obesity is a significant risk factor for cardiometabolic diseases.
• Observational studies suggest links between obesity and psychiatric traits, but causal inference is challenging.
• Mendelian randomization offers a method to investigate causal relationships between exposures and outcomes.

Purpose of the Study:

• To investigate the causal association between body mass index (BMI) and three psychiatric traits: bipolar disorder, schizophrenia, and major depressive disorder.
• To address limitations of observational studies by employing robust genetic methods.
• To provide insights into the complex interplay between physical health and mental well-being.

Main Methods:

• Two-sample Mendelian randomization analysis was utilized.
• Methods included inverse variance weighting, weighted median, and MR-Egger regression.
• Data were sourced from the Genetic Investigation of Anthropometric Traits and Psychiatric Genomics consortia.

Main Results:

• No significant causal effect of BMI on bipolar disorder or schizophrenia was detected.
• Estimates for major depressive disorder suggested a potential positive association, though statistical power was limited.
• Sensitivity analyses indicated potential underestimation of effects for depression, warranting further investigation.

Conclusions:

• The findings do not support a causal role for higher BMI in the development of bipolar disorder and schizophrenia.
• While suggestive, the evidence for a causal link between BMI and major depressive disorder remains weak due to limited statistical power.
• Future research with larger genetic datasets for psychiatric traits is recommended to enhance statistical power and confirm or refute observed associations.