Increased genetic vulnerability to smoking at CHRNA5 in early-onset smokers. by Hartz, S, Short, SE, Saccone, N, Culverhouse, R, Chen, L, Schwantes-An, T, Coon, H, Han, Y, Stephens, S, Sun, J, Chen, X, Ducci, F, Dueker, N, Franceschini, N, Frank, J, Geller, F, Gubjartsson, D, Hansel, N, Jiang, C, Keskitalo-Vuokko, K, Liu, Z, Lyytikäinen, L, Michel, M, Rawal, R, Rosenberger, A