1. Department of Epidemiology and Biostatistics, University of California, San Francisco
2. now at Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison
3. Department of Epidemiology, Jonathan and Karin Fielding School of Public Health, University of California, Los Angeles
4. Department of Psychiatry, University of California, San Francisco
5. Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor