Danish Headache Center (L.J.A.K., A.-L.E., A.F.C., O.B.D., J.O., T.F.H.), Department of Neurology, Rigshospitalet Glostrup, Denmark; Department of Psychiatry and Psychotherapy (S.A., S.R.), Charité-Universitätsmedizin, Berlin, Germany; Analytic and Translational Genetics Unit (S.R.), Massachusetts General Hospital, Boston; Stanley Center for Psychiatric Research (S.R.), Broad Institute of MIT and Harvard, Cambridge, MA; Mental Health Centre Sct Hans (A.I.), Institute of Biological Psychiatry, Roskilde; Department of Clinical Immunology (C.E.), Aarhus University Hospital; Department of Epidemiology Research (H.H.), Statens Serum Institut, Copenhagen; and Department of Clinical Immunology (H.U.), the Blood Bank, Rigshospitalet, Copenhagen University Hospital, Denmark.