[1] Vanderbilt Univ, Med Ctr, Vanderbilt Genet Inst, Dept Med, 1420B Med Ctr East, Nashville, TN 37232 USA
[2] Univ Calif San Diego, Dept Psychiat, La Jolla, CA 92093 USA
[3] Univ Calif San Diego, Ctr Behav Genet Aging, La Jolla, CA 92093 USA
[4] VA Ctr Excellence Stress & Mental Hlth, La Jolla, CA USA
[5] Univ Calif Riverside, Dept Psychol, Riverside, CA 92521 USA
[6] Univ Southern Denmark, Danish Twin Registry, Dept Publ Hlth, Odense C, Denmark
[7] Univ New South Wales Sydney, Sch Psychiat, Ctr Healthy Brain Ageing, Sydney, NSW, Australia
[8] Univ Southern Calif, Ctr Econ & Social Res, Los Angeles, CA 90007 USA
[9] Karolinska Inst, Dept Med Epidemiol & Biostat, Solna, Sweden