Recently, there has been an increasing interest in how diet and nutrition influence both physical and mental health. Numerous studies have highlighted the potential role of B vitamins in neuropsychiatric disorders (NPDs), yet the exact causal relationship between these nutrients and NPDs remains unclear. In our Mendelian randomization (MR) meta-analysis, we examined the links between B vitamins (VB6, VB12, and folate) and NPDs, utilizing data from previous MR studies, the UK Biobank, and FinnGen databases. Our MR analysis revealed a complex, multifaceted association: VB6 appears to protect against Alzheimer's disease (AD) but may increase the risk for conditions such as major depressive disorder and post-traumatic stress disorder. VB12 seems protective against autism spectrum disorder (ASD) but may heighten the risk for bipolar disorder (BD). Folate has shown protective effects against AD and intellectual disability (ID). The meta-analysis suggests that B vitamins may protect against certain disorders like AD and Parkinson's disease, but they might also be risk factors for anxiety and other psychiatric conditions. Further subgroup analysis indicates that VB6 protects against epilepsy and schizophrenia but increases the risk of mania
VB12 protects against ID and ASD but raises the risk of schizophrenia and BD
folate protects against schizophrenia, AD, and ID. These findings reveal the intricate influence of B vitamins on mental health, emphasizing that different B vitamins have distinct impacts on various NPDs. This complexity underscores the importance of personalized supplementation in developing future therapeutic approaches for NPDs.