This publication was written by Bennett W. Fletcher, Ph.D., Redonna K. Chandler, Ph.D., and the Office of Science Policy and Communications, National Institute on Drug Abuse.

This publication is in the public domain and may be used or reproduced in its entirety without permission from NIDA or the authors. Citation of the source is appreciated.

The U.S. Government does not endorse or favor any specific commercial product or company. Trade, proprietary, or company names appearing in this publication are used only because they are considered essential in the context of the studies described here.