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Randomized controlled trial of a novel cannabis use intervention delivered by telephone


Correspondence to: Peter Gates, National Cannabis Prevention and Information Centre, University of New South Wales, PO Box 684, Randwick, NSW 2031, Australia. E-mail:



To evaluate the efficacy of a telephone-based intervention consisting of four sessions of motivational interviewing (MI) and cognitive behavioural therapy (CBT) designed to assist individuals to reduce their cannabis use and related problems.


Random allocation to intervention or delayed treatment control with 4- and 12-week follow-up assessments.


Counsellors from the Cannabis Information and Helpline (CIH), an Australian reactive telephone service, delivered the intervention to callers seeking treatment.


A total of 160 participants were recruited by the CIH, with 110 participants completing the final follow-up assessment (69% retention).


Cannabis use, dependence and related problems and other substance use were assessed at baseline and follow-up.


Intervention participants reported greater reductions in dependence symptoms [P < 0.001, d = 0.9 (0.5–1.3)] and related problems [P < 0.001, d = 0.5 (0.1–0.9)] compared with control participants at both follow-up assessments. Compared with control, intervention participants reported greater confidence to reduce cannabis use at 4 weeks [P = 0.002, d = 0.5 (0.1–0.9)], and in turn reported a greater percentage of abstinent days at 12 weeks [P = 0.019, d = 0.6 (0.2–1.0)].


A brief course of motivational interviewing plus cognitive behavioural therapy delivered by telephone can help to reduce cannabis dependence and promote abstinence in the short term.