[1] Stanford Univ, Dept Psychol, Stanford, CA 94305 USA
[2] Stanford Univ, Div Pain Med, Dept Anesthesiol Perioperat & Pain Med, Stanford, CA 94305 USA
[3] Univ Calif Davis, Betty Irene Moore Sch Nursing, Davis, CA 95616 USA
[4] Stanford Univ, Dept Psychiat & Behav Sci, Stanford, CA 94305 USA