[1] Stanford Univ, Dept Emergency Med, Stanford, CA 94304 USA
[2] Stanford Univ, Dept Psychiat, Stanford, CA 94304 USA
[3] Univ Utah, Dept Phys Med & Rehabil, Salt Lake City, UT 84108 USA
[4] Stanford Univ, Dept Sports Med, Stanford, CA 94304 USA
[5] Stanford Univ, Brain Performance Ctr, Dept Neurosurg, Stanford, CA 94304 USA