[1] Drexel Univ, Sch Publ Hlth, Dept Epidemiol & Biostat, Philadelphia, PA 19102 USA
[2] Drexel Univ, Sch Med, Dept Med, Philadelphia, PA 19102 USA
[3] Univ Penn, Sch Med, Dept Psychiat, Philadelphia, PA 19104 USA
[4] Univ Penn, Sch Med, Dept Anesthesiol, Philadelphia, PA 19104 USA
[5] Philadelphia Vet Affairs Med Ctr, Pain Management Serv, Philadelphia, PA USA