rs5886709

A bidirectional two-sample Mendelian randomization study examining the causal relationship between 25-hydroxyvitamin D levels and attention-deficit/hyperactivity disorder (ADHD). Using 79,366 European individuals for vitamin D GWAS data and 19,099 ADHD cases with 34,194 controls, the study found no evidence of a causal effect of vitamin D on ADHD (IVW β = -0.043, p = 0.833) or reverse causality. Although rs12785878 showed a nominal association with increased ADHD risk at higher vitamin D levels (p = 0.024), this did not survive multiple testing correction.