Causal link identified between bipolar disorder, IBD

Bipolar disorder (BD) is causally associated with inflammatory bowel disease (IBD), according to a study published online Sept. 20 in Frontiers in Genetics.

Zhe Wang, from the First Affiliated Hospital, China Medical University in Shenyang, and colleagues performed bidirectional two-sample Mendelian randomization (MR) and selected single nucleotide polymorphisms (SNPs) associated with BD and IBD. SNPs and genetic associations with BD and IBD were obtained from the latest genome-wide association studies in Europeans.

The researchers found a significant, positive association for genetically predicted BD with the risk for IBD and ulcerative colitis (per log-odds ratio increase: odds ratios, 1.18 and 1.19, respectively). In a validation analysis, the combined odds ratios of IBD, Crohn disease, and UC increased per log-odds ratio of BD (odds ratios, 1.16, 1.20, and 1.17, respectively). No causal relationship was seen between genetically influenced IBD and BD.

"Our results confirm a causal relationship between BD and IBD, which may influence clinical decisions on the management of BD patients with intestinal symptoms," the authors write. "Although the reverse MR results did not support a causal effect of IBD on BD, the effect of active IBD on BD remains to be further investigated."