[1] Univ N Carolina, Dept Psychiat, Sch Med, Chapel Hill, NC 27515 USA
[2] Univ N Carolina, Sch Med, Carolina Inst Dev Disabil, Chapel Hill, NC 27515 USA
[3] Michigan State Univ, Dept Pediat & Human Dev, Inst Quantitat Hlth Sci & Engn, E Lansing, MI 48824 USA
[4] Univ N Carolina, Dept Phys Med & Rehabil, Sch Med, Chapel Hill, NC 27515 USA
[5] RTI Int, Res Triangle Pk, NC USA
[6] Univ N Carolina, Sch Med, Dept Psychol & Neurosci, Chapel Hill, NC 27515 USA
[7] Univ N Carolina, Frank Porter Graham Child Dev Inst, Chapel Hill, NC 27515 USA
[8] Univ N Carolina, Sch Med, Dept Pediat, Chapel Hill, NC 27515 USA
[9] Univ N Carolina, Sch Med, Dept Allied Hlth Sci, Chapel Hill, NC 27515 USA