[1] Univ North Carolina Chapel Hill, Gillings Sch Global Publ Hlth, Dept Epidemiol, Campus Box 7435,McGavran Greenberg Hall, Chapel Hill, NC 27599 USA
[2] Johns Hopkins Univ, Dept Epidemiol, Bloomberg Sch Publ Hlth, Baltimore, MD USA
[3] Johns Hopkins Univ, Dept Mental Hlth, Bloomberg Sch Publ Hlth, Baltimore, MD USA
[4] Johns Hopkins Univ, Dept Biostat, Bloomberg Sch Publ Hlth, Baltimore, MD USA
[5] Johns Hopkins Univ, Dept Hlth Policy & Management, Bloomberg Sch Publ Hlth, Baltimore, MD USA