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Research Summary

Cannabis Use in Adolescents: Efficacy of a Prevention-Focused Brief Intervention in Primary Care

In the U.S., rates of illicit cannabis use typically increase during adolescence. Primary care visits may be a good opportunity to provide prevention-focused brief interventions (BI) for cannabis use in this population. In this trial, adolescents aged 12–18 (n=714) who reported no lifetime use of cannabis were randomized to a motivational interview-based prevention BI with a therapist, an animated interactive computer-based prevention BI, or to a control group (brochure). Both interventions provided cannabis and alcohol norms for age and gender and explored goals and values, reasons for avoiding use, and risky scenarios (with a focus on refusal skills).

  • Compared with controls, participants who received the computer BI reported lower rates of any cannabis use over 12 months (17% versus 24%) and lower frequency of use at 3 and 6 months.
  • There were no significant differences between controls and participants who received the therapist BI in rate or frequency of cannabis use.
  • With respect to the use of other drugs at 3 months, differences in favor of the interventions were observed between controls and those who received the computer BI or the therapist BI. For alcohol use at 6 months and delinquency at 3 months, differences were observed between controls and those who received the therapist BI.


This is the first trial of a primary prevention-focused brief intervention in primary care for self-reported illicit cannabis use in adolescents. The effects were small and dissipated over time, but a computer-based BI appears to be a promising approach for prevention. Questions remain about the optimal content of the BI and whether repeating these interventions over time may increase or prolong their efficacy, and whether intervention effects could be confirmed with biological measures of use. Nicolas Bertholet, MD, MSc


Walton MA, Resko S, Barry KL, et al. A randomized controlled trial testing the efficacy of a brief cannabis universal prevention program among adolescents in primary care. Addiction. 2014;109(5):786–797.