The effect of baseline cocaine use on treatment outcomes for heroin dependence over 24 months: findings from the Australian Treatment Outcome Study

AIMS: The aim of this study was to determine the effects of baseline cocaine use on treatment outcomes for heroin dependence over a 24-month period. DESIGN: A longitudinal cohort (24 months) study was carried out. Interviews were conducted at baseline, 3, 12, and 24 months. SETTING: The study setting was Sydney, Australia. PARTICIPANTS: Six hundred fifteen heroin users were recruited for the Australian Treatment Outcome Study. FINDINGS: Cocaine use was common at baseline (40%) but decreased significantly over the study period. Even after taking into account age, sex, treatment variables, current heroin use, and baseline polydrug use, baseline cocaine use remained a significant predictor of poorer outcomes across a range of areas. Baseline cocaine users were more likely to report heroin use, unemployment, needle sharing, criminal activity, and incarceration over the 24-month study period. CONCLUSIONS: Cocaine consumption among heroin users has repercussions across a range of areas that persist far beyond the actual period of use. Consequently, treatment providers should regard cocaine use among clients as an important marker for individuals who are at risk of poorer treatment outcome.