Thomas McLellan, Ph.D

A. Thomas McLellan, Ph.D., is a psychologist, professor of psychiatry at the University of Pennsylvania and founder and Executive Director of the Treatment Research Institute, a not-for-profit research and evaluation institute in Philadelphia.

McLellan was the principal developer of the Addiction Severity Index (ASI) and the Treatment Services Review (TSR), measurement instruments that characterize the multiple dimensions of substance abusing patients and treatments.  These tools have been translated into over 20 languages and are the most widely used instruments of their kind in the world.  They were created with the view that substance abuse and addiction could not be adequately understood and addiction treatments could not be adequately delivered if there were no relevant real world methods to gauge them.  The ASI and TSR have helped to revolutionize the delivery of treatment and helped researchers and clinicians gain more insight into the efficacy of treatment.

McLellan’s work has also promoted better understanding of the factors that lead to treatment success, and has fostered greater understanding of addiction as a chronic illness, reduced its stigma, and provided means for earlier identification and prevention.  McLellan and his colleagues are currently researching the active and inactive ingredients of treatment, the appropriate duration and content of treatment for various types of patients, and ways of transferring findings from treatement research into practical applications for the practitioner and provider.

In 1992, McLellan founded the Treatment Research Institute as an independent, not-for-profit institute dedicated to taking scientific methods and findings from controlled studies and using them in real-world studies to give science an opportunity to influence clinical practice and public policy.

McLellan has published more than 400 articles and chapters on addiction research and serves as editor in chief of the Journal of Substance Abuse Treatment.  He serves on the editorial boards and as a reviewer of numerous medical and scientific journals.

He has served as an advisor to many government and nonprofit scientific organizations, including the Office of National Drug Control Policy, Research and Evaluation; the National Practice Laboratory of the American Psychiatric Association, the Swiss National Science Foundation, the World Health Organization, and the Greek government.

Among McLellan’s many honors and awards are the Life Achievement Award of the American Society of Addiction Medicine in 2003 and the 2002 award for Distinguished Contribution in Addiction Medicine from the Swedish Medical Association.

McLellan received his B.A. from Colgate University and his M.S. and Ph.D. from Bryn Mawr College.  He received postgraduate training in psychology at Oxford University in England.