Authors: Caroline Salom and Kim Betts

Are more harms associated with some injectable drugs than others? Is it worse to use substances singly or in combination?  Do opioid substitution therapies, such as methadone, reduce these risks?

ISSR researchers, Professor Rosa Alati, Dr Kim Betts, Dr Fairlie McIlwraith and Dr Caroline Salom, used the Illicit Drug Reporting System (IDRS) to answer these questions and profile users in order to understanding use patterns and associated risks. The IDRS processes an annual collection of data comprising interviews with regular substance users, expert knowledge (such as drug trends), and related indicator data, and generating information about use patterns and harms associated with use, along with pricing, purity and availability of heroin, methamphetamine, cocaine and cannabis. The frequency of data collection ensures that it is sensitive to trends and provides data in a timely manner.

In addition to collecting and reporting on data for Queensland, ISSR researchers are teasing out useful patterns hidden deep within the data, which may hold importance for the health of substance users. Of particular interest are patterns of polysubstance use, as individuals using multiple substances tend to be more opportunistic, rather than deliberate, in their drug selection. Surprisingly, typical use by this group may include both opioids (such as heroin or pharmaceutical oxycodone) and stimulants (such as cocaine or methamphetamine). With multiple substances contributing in different ways to users’ health and other outcomes, the researchers applied a clustering technique through the system to group people based on similarities, allowing them to better assess the relationships between drug use and health outcomes.

One key finding derived from applying this technique to the last round of data was a clear link between broad (opportunistic) polysubstance use and injection-related harms such as thromboses and abscesses, violent criminal offending, and mental health problems. Looking specifically at substance users with mental health problems, it was found that co-use of cocaine and heroin was particularly detrimental to the risk of non-fatal overdose.  Interestingly, the increased risk in this group was not due to a greater frequency or amount of cocaine and heroin injected, suggesting a need for the research on particular risks presented by combining opioids with stimulants.

This research also identified polysubstance use characterised by both a broad mix of drugs and drug types as increasing the risk of poor health and violent criminal involvement, and placing distressed individuals at elevated risk of non-fatal overdose. These findings present clear targets for intervention efforts and a guide for future studies to explore this area in greater detail. 

The IDRS is funded by the Australian Government Department of Health and is coordinated by the National Drug and Alcohol Research Centre (NDARC) at the University of New South Wales. 

For more information about this research, contact Professor Rosa Alati or


05 October 2017