Reducing Heroin Use Did Not Lead to Increased Use of Other Drugs Including Cannabis | Research

The takeaway

A 2-year study of 615 heroin users found that reducing heroin use was associated with reduced use of most other drugs, not increased substitution, though cannabis and alcohol use were unrelated to heroin use changes.

Read this if you want to know whether reducing one drug leads to increased use of other substances.

No evidence for drug substitution: reducing heroin was associated with reducing most other drugs too

What the researchers found

Researchers followed 615 heroin users recruited for the Australian Treatment Outcome Study at 3, 12, and 24 months. The proportion reporting weekly heroin use declined significantly at all time points.

Reductions in heroin use were associated with less frequent use of other opioids, cocaine, amphetamine, and benzodiazepines. Alcohol use remained stable throughout. Cannabis and alcohol use were unrelated to changes in heroin use.

Longer periods in residential rehabilitation were associated with declines across all drug classes. Maintenance treatment was associated with declines in other opioid and alcohol use specifically. The study found no evidence for drug substitution, directly challenging the concern that reducing heroin use would push people to other substances.

Why it matters

The fear that treating one addiction simply shifts people to another substance is a common concern that can discourage treatment-seeking. This study provides evidence against that substitution hypothesis, showing that successful heroin reduction tends to coincide with reduced use of most other substances as well.

The numbers in context

615 heroin users followed for 24 months. Weekly heroin use declined at all time points. Use of other opioids, cocaine, amphetamine, and benzodiazepines also declined. Cannabis and alcohol use were unrelated to heroin changes. Residential rehab associated with declines across all drug classes.

How the study worked

Longitudinal cohort study with follow-up at 3, 12, and 24 months. Six hundred fifteen heroin users in New South Wales, Australia. Assessed frequency of use across multiple substance categories at each time point.

What this study cannot tell us

Limited to treatment-seeking heroin users in one Australian state, which may not generalize to other populations. Self-reported drug use may underestimate actual consumption. The study cannot determine whether reduced use of other drugs was caused by heroin treatment or by general lifestyle changes associated with treatment engagement.

How to read the evidence

Longitudinal cohort study with multi-point follow-up and adequate sample size. Unable to establish causation but strong observational evidence.

When this study was published

Published in 2006. Subsequent research has generally supported the finding that successful addiction treatment does not typically lead to drug substitution.

The bigger picture

The independence of cannabis use from heroin use patterns in this study is notable. It suggests cannabis use among polysubstance users may be driven by different factors than opioid or stimulant use, and that changes in heroin use do not systematically affect cannabis consumption.

Questions still open

Why were cannabis and alcohol use patterns independent of heroin use changes? Does the lack of substitution hold for longer follow-up periods and in different treatment settings?

Common questions

Does quitting heroin make people use more cannabis?

No. In this study, cannabis use was unrelated to changes in heroin use. People who reduced heroin use did not increase their cannabis consumption.

Does treating one addiction just create another?

This study found no evidence for drug substitution. Reducing heroin use was associated with reduced use of most other drugs (opioids, cocaine, amphetamines, benzodiazepines), not increased use.

Read the original research

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

Drug and alcohol dependence, 84(2), 201-5

View on PubMed ↗

Citation

Darke, Shane; Williamson, Anna; Ross, Joanne; Teesson, Maree. (2006). Reductions in heroin use are not associated with increases in other drug use: 2-year findings from the Australian Treatment Outcome Study.. Drug and alcohol dependence, 84(2), 201-5.