1. Heinz College, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA;
2. RAND Drug Policy Research Center, Santa Monica, California 90407, USA
3. Department of Criminology and Criminal Justice and School of Public Policy, University of Maryland, College Park, Maryland 20742, USA
4. RAND Corporation, Pittsburgh, Pennsylvania 15213, USA
5. University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA