[1] Kaiser Permanente Colorado, Inst Hlth Res, POB 378066, Aurora, CO 80037 USA
[2] Colorado Permanente Med Grp, Chem Dependency Treatment Serv, Aurora, CO USA
[3] Univ Colorado, Dept Med, Div Gen Internal Med, Sch Med, Aurora, CO USA
[4] Kaiser Permanente Bernard J Tyson Sch Med, Dept Hlth Syst Sci, Pasadena, CA USA
[5] Kaiser Permanente Southern Calif, Dept Res & Evaluat, Pasadena, CA USA
[6] Marshfield Clin Res Inst, Ctr Clin Epidemiol & Populat Hlth, Marshfield, WI USA
[7] Denver Hlth & Hosp Author, Ctr Hlth Syst Res, Off Res, Denver, CO USA
[8] Colorado Sch Publ Hlth, Dept Epidemiol, Aurora, CO USA