Modelling Long-Term Joint Trajectories of Heroin Use and Treatment Utilisation: Findings from the Australian Treatment Outcome Study

BACKGROUND: Heroin is currently contributing to the worst drug addiction epidemic in United States history; recent rates of use, dependence and death have also increased dramatically in parts of Europe. An improved understanding of the long-term relationship between heroin use and treatment utilisation is essential to inform both clinical and public health responses. We aimed to identify i) joint trajectories of heroin use and treatment utilisation, ii) predictors of joint group membership, and iii) outcomes associated with joint group membership; over 10-11 years among a cohort of Australians with heroin dependence. METHODS: A total of 615 people with heroin dependence were recruited as part of a prospective longitudinal cohort study between 2001 and 02. This analysis focuses on 428 participants (70.1% of the original cohort) for whom complete data were available over 10-11 years. FINDINGS: Five joint trajectory groups were identified: i) 'long-term stable' (17%: decrease in probability of heroin use alongside high treatment utilisation); ii) 'long-term success' (13%: decrease in heroin use alongside decreased treatment utilisation, until there was maintained abstinence from heroin with no treatment utilisation); iii) 'treatment failure' (12%: no decrease in heroin use alongside high treatment utilisation); iv) 'late success' (9%: gradual decrease in heroin use alongside increased treatment utilisation); and v) 'relapsed' (9%: relapse in heroin use alongside an increase and decrease in treatment utilisation). Few variables were found to predict joint group membership, but group membership was predictive of demographic, substance use and physical and mental health outcomes at 10-11 years. INTERPRETATION: The role of treatment in recovery from heroin dependence is undeniable; however, a considerable proportion of people are able achieve and maintain abstinence without the need for ongoing treatment. An equally significant proportion will continue to use heroin despit