1. Clinical Addiction Research and Education Unit, Section of General Internal Medicine, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts2Department of Medicine, Boston Medical Center, Boston, Massachusetts
2. Department of Epidemiology and Biostatistics, University of California, San Francisco
3. Department of Medicine, University of California, San Francisco
4. Department of Epidemiology and Biostatistics, University of California, San Francisco4Department of Medicine, University of California, San Francisco
5. Division of Epidemiology, Biostatistics and Preventive Medicine, Department of Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque