Hair cortisol in twins: Heritability and genetic overlap with psychological variables and stress-system genes von Rietschel, L, Streit, F, Zhu, G, McAloney, K, Frank, J, Couvy-Duchesne, B, Witt, SH, Binz, TM, McGrath, J, Hickie, IB, Hansell, NK, Wright, MJ, Gillespie, NA, Forstner, AJ, Schulze, TG, Wüst, S, Nöthen, MM, Baumgartner, MR, Walker, BR, Crawford, AA, Colodro-Conde, L, Medland, SE, Martin, NG, Rietschel, M, Mahajan, A, Lindgren, C, Morris, AP, CORtisolNETwork (CORNET) Consortium, Major Depressive Disorder Working Group of the Psychiatric Genomics Consortium (PGC)