Genetic identification of cell types underlying brain complex traits yields insights into the etiology of Parkinson's disease. af Bryois, J, Skene, NG, Hansen, TF, Kogelman, LJA, Watson, HJ, Liu, Z, Eating Disorders Working Group of the Psychiatric Genomics Consortium, International Headache Genetics Consortium, 23andMe Research Team, Brueggeman, L, Breen, G, Bulik, CM, Arenas, E, Hjerling-Leffler, J, Sullivan, PF