1. Department of Family Medicine, Boston Medical Center and Boston University School of Medicine, Boston, Massachusetts
2. Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
3. Health Policy Research Center, Massachusetts General Hospital, Boston, Massachusetts
4. Department of Rehabilitation Science, Massachusetts General Hospital Institute of Health Professions, Boston, Massachusetts
5. School of Physical Therapy, Massachusetts College of Pharmacy and Health Sciences, Worcester, Massachusetts
6. Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts
7. Kaiser Permanente Washington Health Research Institute, Seattle, Washington
8. Department of Epidemiology, University of Washington, Seattle, Washington, USA