Causal relationship between bipolar disorder and inflammatory bowel disease: A bidirectional two-sample mendelian...

Area of Science:

• Genetics and Epidemiology
• Psychiatry and Gastroenterology

Background:

• Observational studies suggest a link between bipolar disorder (BD) and inflammatory bowel disease (IBD), but confounding factors hinder causal inference.
• Understanding the directionality of the BD-IBD association is crucial for clinical management and patient care.

Purpose of the Study:

• To investigate the causal relationship between bipolar disorder (BD) and inflammatory bowel disease (IBD) using bidirectional two-sample Mendelian randomization (MR).
• To determine if BD influences IBD risk or if IBD affects BD development.

Main Methods:

• Utilized two-sample Mendelian randomization (MR) with single nucleotide polymorphisms (SNPs) from large genome-wide association studies (GWAS) for BD and IBD in European populations.
• Employed inverse-variance-weighted (IVW) as the primary analysis method, with MR-Egger, simple mode, and weighted median for sensitivity analyses and quality control.

Main Results:

• Genetically predicted BD was significantly associated with an increased risk of IBD (OR: 1.18) and ulcerative colitis (UC) (OR: 1.19), but not Crohn's disease (CD).
• Reverse MR analyses did not support a causal effect of IBD on BD.
• Validation analyses confirmed the association of BD with IBD and UC risk.

Conclusions:

• Confirmed a causal effect of bipolar disorder (BD) on the risk of developing inflammatory bowel disease (IBD), particularly UC.
• The findings suggest BD management may need to consider gastrointestinal health, especially in patients with intestinal symptoms.
• Further research is needed to explore the potential impact of IBD's active disease phase on BD.