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Abstract
A minority of cannabis users will experience problematic use or be diagnosed with a cannabis use disorder. As cannabis is the most commonly used illicit drug, this minority represents a significant number of individuals. Notably, however, few will attend treatment to reduce their use. Heavy, regular cannabis users commonly report a lack of motivation to enter face-to-face treatments and a wish to avoid the stigma associated with accessing illicit drug treatment. A telephone-based intervention may be ideal as ambivalent treatment seekers can maintain anonymity to a greater extent compared to face-to-face treatment, would not be required to travel, and could receive inexpensive information or counselling as needed. Telephone-based substance use intervention research is almost exclusive to tobacco and alcohol use. The present thesis extends this research by developing and evaluating a telephone-based cannabis treatment (the Cannabis Assistance HelpLine, or CAHL intervention) as an extension to the usual service of the Cannabis Information and Helpline (CIH) in Australia. First, the demographic and substance use profile of callers to the CIH was described. Second, an impact evaluation survey was conducted with 200 callers to the CIH, and patterns of utilisation and predictors of satisfaction were established. Third, based on the impact evaluation, the CAHL intervention was developed and CIH counsellors were trained to deliver the intervention. Finally, 160 individuals were randomly allocated to receive the CAHL intervention (n=79) or a delayed treatment control (n=81). Baseline and four- and 12-week follow-up interviews surveyed the participants cannabis use frequency and quantity, cannabis dependence severity and related problems, and aspects of physical and mental health. Intervention participants reported greater reductions in cannabis dependence severity (Cohen s d=0.9) and cannabis-related problems (d=0.5) compared to the wait-list control at both follow-up assessments. Treatment outcomes were comparable to face-to-face intervention trials, and reductions in cannabis use were partially driven by the intervention effect of increasing confidence to avoid cannabis use. The telephone delivery of cannabis treatment is a promising means to extend the reach of healthcare without compromising on outcome. Future work to improve telephone-based cannabis interventions is discussed.