Background: The use of brief intervention for decreasing frequent marijuana use holds potential, but its efficacy in primary care is not known.
Objective: To assess the impact of 2 brief interventions on marijuana use among daily/or almost daily marijuana users.
Design: Subgroup analysis of a 3-arm randomized clinical trial of 2 brief counseling interventions compared with no brief intervention on daily marijuana use in a primary care setting (ASPIRE).
Participants: ASPIRE study participants who both reported 21-30 days of marijuana use during the past month and identified marijuana as their drug of most concern.
Interventions: (1) brief negotiated interview (BNI), a 10-15-minute structured interview, and (2) an adaptation of motivational interviewing (MOTIV), a 30-45-minute intervention. Control group participants received only a list of substance use treatment resources.
Main measures: The primary outcome was number of days of marijuana use in the past 30 days at the 6-month follow-up. Secondary outcomes were (1) number of days of marijuana use at 6-week follow-up and (2) drug problems (Short Inventory of Problems-Drugs, SIP-D) at 6-week and 6-month follow-ups. Differences between intervention groups were analyzed using negative binomial regression models.
Results: Among the 167 eligible participants, we did not find any significant impact of either of the 2 interventions on past 30 days of marijuana use at 6 months (adjusted incidence rate ratio [aIRR]: 0.95, 95% confidence interval [CI]: 0.75-1.15, P = .82 for BNI vs. control; aIRR: 1.02, 95% CI: 0.85-1.23, P = .82 for MOTIV vs. control). There was no significant impact on drug-related problems at 6-month follow-up (aIRR: 1.12, 95% CI: 0.69-1.82, P = .66 and aIRR: 1.46, 95% CI: 0.89-2.38, P = .27 for BNI vs. control and MOTIV vs. control, respectively). Results were similar at 6 weeks.
Conclusions: Brief intervention has no apparent impact on marijuana use or drug-related problems among primary care patients with frequent marijuana use identified by screening.
Keywords: Brief intervention; marijuana; primary care; screening.