[1] Boston Med Ctr, Clin Addict Res & Educ Unit, Boston, MA 02118 USA
[2] Boston Univ, Sch Med, Dept Med, Boston, MA 02215 USA
[3] Boston Med Ctr, Dept Family Med, Boston, MA 02118 USA
[4] Boston Med Ctr, Dept Pediat, Boston, MA 02118 USA
[5] Boston Univ, Sch Med, Boston, MA 02215 USA
[6] Boston Univ, Sch Publ Hlth, Dept Biostat, Boston, MA 02215 USA
[7] Boston Univ, Sch Publ Hlth, Data Coordinating Ctr, Boston, MA 02215 USA
[8] ABT Associates Inc, Cambridge, MA 02138 USA
[9] Boston Univ, Sch Med, Dept Pediat, Boston, MA 02215 USA