Treating cannabis dependence: findings from a multi-site study

First published: 30 March 2019 | Last updated: 20 May 2019


Dr Tom Babor

Associate Editor-in-Chief, Addiction

Dr. Babor is a Professor and Chairman in the Department of Community Medicine and Health Care, University of Connecticut School of Medicine.  He holds the University’s Physicians Health Service endowed chair in Public Health and Community Medicine.  Dr. Babor received his doctoral degree in social psychology from the University of Arizona.  He spent several years in postdoctoral research training in social psychiatry at Harvard Medical School, and subsequently served as head of social science research at McLean Hospital’s Alcohol and Drug Abuse Research Center in Belmont, Massachusetts.  In 1982, Dr. Babor moved to the Department of Psychiatry at the University of Connecticut School of Medicine, Farmington, Connecticut.  He was the Scientific Director of the Alcohol Research Center between 1992 and 1994 and Interim Chair of the Department of Psychiatry between 1994 and 1998.  He has also served as Principal Investigator of the Coordinating Center of Project MATCH, as well as several other multi center clinical trials of treatment for alcoholism and drug abuse.  Since 1997 he has been chairman of the Department of Community Medicine and Health Care at the University of Connecticut School of Medicine.  He is Associate Editor-in-Chief as well as Regional Editor of the international journal, Addiction.  His research interests include alcohol and drug screening, diagnosis, early intervention, and treatment evaluation, as well as alcohol and drug policy.

This presentation describes the results ofthe Marijuana Treatment Project (MTP), a three-site randomized clinical trial that investigated the efficacy of treatment interventions with 450 chronic marijuana users. Participants randomized to three treatment groups: 1) a two-session condition guided by Motivational Enhancement Therapy (MET); 2) a nine-session condition that guided by MET, cognitive-behavioural therapy and case management; 3) a delayed treatment control condition. Participants were evaluated at intake to tlfe study, at the end of
treatment, and again at 4, 9, 15 and months post-randomization. The results showed that the nine-session treatment reduced marijuana smoking significantly more than the two-session treatment, and that both groups declined more than the delayed treatment control group. These results, based on self-reported marijuana consumption, were replicated with urine toxicology data. The significant reductions in marijuana use were associated with similar treatment-related reductions in depression, marijuana-related problems, and dependence symptoms. No differential effects of treatment by gender, ethnicity (white, nonwhite),or employmentstatus were found, suggesting that the interventions were effective with special population groups. Further analyses using the 9- and 15-month follow-up data showed little deterioration of the treatment effects over time. The results will be discussed in terms of the value and effectiveness of specific treatments for chronic marijuana users.