CUBN and major depressive disorder: For example, the second top association signal in the case-only meta-analysis of BE among BD patients was in the gene encoding cubilin (CUBN), a receptor for the intrinsic factor-vitamin B12 complex, which is essential for neurodevelopment; its deficiency has been implicated in various neuropsychiatric diseases such as depression, schizophrenia, dementia, and cognitive impairment52,53.