Reductions in heroin use are not associated with increases in other drug use: 2-year findings from the Australian Treatment Outcome Study

AimsTo determine whether reductions in frequency of heroin use were associated with reductions in the use of other drugs over a 24-month period.DesignLongitudinal cohort, with follow-up at 3, 12 and 24 months.ParticipantsSix hundred and fifteen heroin users recruited for the Australian Treatment Outcome Study.SettingNew South Wales, Australia.FindingsThe proportion reporting weekly heroin use declined significantly at 3, 12 and 24 months. Reductions in heroin use were associated with longer periods in both residential rehabilitation (RR) and maintenance treatment (MT). Less frequent use of other opioids, cocaine, amphetamine, cannabis and benzodiazepines were noted over follow-up, with alcohol use remaining stable. Across follow-up, lower frequency heroin use was associated with reduced likelihood of frequent use of other opioids, cocaine, amphetamine and benzodiazepines. Alcohol and cannabis use were unrelated to heroin use. Longer periods spent in RR were associated with declines in the use of all other drug classes, with MT associated with declines in other opioid and alcohol use.ConclusionsThere was no evidence for drug substitution in the face of reduced heroin use in this cohort of treatment seekers. The fear that a successful reduction in heroin use amongst treatment seekers will precipitate an increase in the use of other drugs appears ill-founded.