[1] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Epidemiol, 130 DeSoto St,5120 Publ Hlth, Pittsburgh, PA 15261 USA
[2] Univ Pittsburgh, Sch Med, Dept Psychiat, Pittsburgh, PA 15261 USA
[3] Calif Pacific Med Ctr Res Inst, San Francisco, CA USA
[4] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA USA