[1] McGill Univ, Jewish Gen Hosp, Lady Davis Inst Med Res, Montreal, PQ H3T 1E2, Canada
[2] Kings Coll London, Dept Twin Res & Genet Epidemiol, London WC2R 2LS, England
[3] Univ Zurich, Inst Psychol, Zurich, Switzerland
[4] McGill Univ, Dept Med, Montreal, PQ H3T 1E2, Canada
[5] McGill Univ, Dept Psychiat, Montreal, PQ H3T 1E2, Canada
[6] McGill Univ, Dept Epidemiol Biostat & Occupat Hlth, Montreal, PQ H3T 1E2, Canada
[7] McGill Univ, Dept Educ & Counseling Psychol, Montreal, PQ H3T 1E2, Canada
[8] McGill Univ, Sch Nursing, Montreal, PQ H3T 1E2, Canada