[1] Northwestern Univ, Dept Prevent Med, 680 North Lake Shore Dr, Chicago, IL 60647 USA
[2] Northwestern Univ, Dept Gen Internal Med, Chicago, IL 60611 USA
[3] Brown Univ, Dept Publ Hlth, Providence, RI 02903 USA
[4] Univ Illinois, Dept Psychol, Chicago, IL 60607 USA
[5] Univ Calif San Francisco, Div Gen Internal Med, San Francisco, CA 94115 USA