Deriving Mendelian Randomization-based Causal Networks of Brain Imaging Phenotypes and Bipolar Disorder.

Area of Science:

• Neuroscience
• Psychiatry
• Genetics

Background:

• Observational studies suggest neuroanatomical differences in bipolar disorder (BD).
• Causal relationships between brain structure and BD remain unclear.

Purpose of the Study:

• To explore the causal dynamics between neuroimaging phenotypes and bipolar disorder (BD).
• To determine if neuroanatomical variations cause or are a consequence of BD.

Main Methods:

• Mendelian randomization analysis of 297 neuroimaging phenotypes from UK BioBank.
• Genome-wide association study summary statistics for BD.
• Inverse sparse regression to estimate direct effects.

Main Results:

• Identified 28 significant causal relationship pairs between neuroimaging and BD.
• 27 pairs indicated neuroimaging phenotypes influencing BD.
• White matter tract phenotypes showed larger causal effects on BD than vice versa.

Conclusions:

• Neuroanatomical variation, particularly in white matter tracts, is a potential cause of bipolar disorder (BD).
• Findings support the hypothesis that specific white matter variations precede BD onset.