[1] Washington Univ, Dept Neurol, St Louis, MO 63110 USA
[2] Washington Univ, Inst Publ Hlth, St Louis, MO 63110 USA
[3] Univ Johannesburg, Fac Humanities, Dept Psychol, Johannesburg, South Africa
[4] George Washington Univ, Sch Med & Hlth Sci, Dept Clin Res & Leadership, Washington, DC 20052 USA
[5] Washington Univ, Div Biostat, St Louis, MO 63110 USA
[6] Washington Univ, Ctr Clin Studies, St Louis, MO 63110 USA