Analyses of drug markets over many years have shown that the price and purity of illicit substances can have a key role in shaping drug consumption, and in turn drug-related harm. For example, international research has shown that decreases in the price of pure heroin can be associated with increased emergency room presentations or heroin‐related overdose hospital admissions (see for example, Caulkins, 2001; Unick et al. 2014). However, it remains unknown to what extent these relationships vary by time, place and drug type. Clarifying the relationship between price, purity and drug-related harm is important for informing targeted law enforcement and harm minimisation strategies.
This study employed a rapid review methodology—a form of evidence synthesis that provides a rigorous method for locating, appraising and synthesising evidence from previous studies, and producing results in a timelier manner than a systematic review (Ganann, Ciliska & Thomas 2010). Consistent with rapid review methodologies, this study was designed in consultation with the funders (the Australian Institute of Criminology) and involved one principal coder and tight inclusion criteria. A four-stage search strategy was employed involving five-peer reviewed databases, grey literature, google scholar and cross-checks with three international scholars.
A total of 1,088 records were identified, and 36 studies were included in the analysis. All included studies were published in the English language between 1990 and March 2019 (when the searches were conducted) and involved empirical, quantitative studies related to drug prices, purity and at least one of the population level harms specified above. A data extraction spreadsheet was used to ensure that consistent information was coded from each study including on context, study design, data source on price and purity, trends in raw price, raw purity and purity adjusted price, nature of relationship between PAP and drug-related harm (inverse, direct, mixed, null) and impact on drug-related harm (by type of harm).
The first tab of the excel spreadsheet of all downloaded data provides a summary of all included studies. This shows for example that 47% of studies came from North America and 42% from Australasia. It also shows that there were two main study types—analyses of specific supply events (eg the Australian heroin shortage) and non-event analyses focusing on purity adjusted price trends over time. These differed significantly in method, quality, breadth and location, and hence warranted separate analyses.
The second tab provides the data extraction from all 36 studies. The third tab includes only studies that involved non-event level studies (n=18) and the fourth tab includes event level studies (n=18).