NRTN and nervous system disorder: In summary, the MR analysis indicated that genetically predicted plasma BDNF levels are causally linked to IL-33, and possibly to 12 circulating inflammatory proteins (Beta-NGF, CASP-8, IL-2, IL-15RA, IL-17 A, IL-17 C, IL-20, IL-20RA, IL-24, LIF, NRTN, and NT-3) shown to be differently involved in the pathogenesis or outcome of several neurological diseases.