ABSTRACT
Aims 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. Design Random allocation to intervention or delayed treatment control with four- and 12-week follow-up assessments. Setting Counsellors from the Cannabis Information and Helpline (CIH), an Australian reactive telephone service, delivered the intervention to callers seeking treatment. Participants A total of 160 participants were recruited by the CIH, with 110 participants completing the final follow-up assessment (69% retention). Measurements Cannabis use, dependence and related problems, and other substance use, were assessed at baseline and follow-up. Findings 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 four weeks (p=0.002, d=0.5 [0.1-0.9]), and in turn reported a greater percentage of abstinent days at twelve weeks (p=0.019, d=0.6 [0.2-1.0]). Conclusions A brief course of motivational interviewing plus cognitive behavioural therapy delivered by telephone can help reduce cannabis dependence and promote abstinence in the short term.