[1] Univ Calif San Francisco, Dept Dermatol, 2341 Sutter St,Room N421, San Francisco, CA 94115 USA
[2] Univ Penn, Perelman Sch Med, Dept Dermatol, Philadelphia, PA 19104 USA
[3] Univ Calif San Francisco, Dept Psychiat & Behav Sci, San Francisco, CA 94115 USA
[4] Univ Calif San Francisco, Dept Pediat, San Francisco, CA 94115 USA
[5] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94115 USA
[6] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, London, England
[7] Univ Calif Berkeley, Sch Publ Hlth, Div Epidemiol, Berkeley, CA 94720 USA