[1] Childrens Natl Med Ctr, Div Adolescent & Young Adult Med, Washington, DC 20010 USA
[2] Univ Tennessee, St Jude Childrens Res Hosp, Div Behav Med, Dept Pediat,Coll Med, Knoxville, TN 37996 USA
[3] George Washington Univ, Sch Med & Hlth Sci, Dept Pediat, Washington, DC 20052 USA
[4] George Washington Univ, Sch Med & Hlth Sci, Dept Epidemiol & Biostat, Washington, DC 20052 USA
[5] George Washington Univ, Sch Med & Hlth Sci, Childrens Res Inst, Childrens Natl Med Ctr, Washington, DC 20052 USA
[6] Gundersen Lutheran Med Fdn Inc, La Crosse, WI USA
[7] Childrens Res Inst, Childrens Natl Med Ctr, Washington, DC USA