[1] Boston University Schools of Medicine and Public Health,the Clinical Addiction Research and Education Unit
[2] Boston University Schools of Medicine and Public Health,Section of General Internal Medicine and the Clinical A1DS Program, Department of Medicine
[3] Boston University School of Medicine and Public Health,Department of Social and Behavioral Sciences
[4] Boston University Schools of Medicine and Public Health,Data Coordinating Center
[5] Smith College,Department of Mathematics
[6] Massachusetts General Hospital,General Medicine Division, Department of Medicine