Volume 205 - Issue 9
Estimating the number of regular and dependent methamphetamine users in Australia, 2002–2014
Authors: Paul M Dietze, Brendan Quinn and Caitlin Hughes
Med J Aust 2016; 205 (9): 425-426. || doi: 10.5694/mja16.00795
Published online: 7 November 2016
Published online: 7 November 2016
N/A
To the Editor:
Estimating the prevalence of illicit drug use is difficult, but reliable estimates are required to understand community needs and inform associated policy and practice.1 Degenhardt and colleagues2 published recent estimates of the prevalence of regular (greater than or equal to monthly use in the past 6 months) and dependent (greater than three on the Severity of Dependence Scale) methamphetamine use in Australia, where the headline figures were an estimated 268 000 and 160 000 regular and dependent methamphetamine users respectively in the 2013–14 financial year.
The published figures used a multiplier approach to generate estimates,1,2 scaling the total number of methamphetamine treatment episodes in Australia by a multiplier that is an estimate of the proportion of methamphetamine users who access methamphetamine-specific treatment. The multiplier was derived from a survey of (predominantly injecting) methamphetamine users in Sydney conducted in late 2003 into early 2004.3
Current methamphetamine market and user characteristics differ markedly from those evident in 2003–04.4 Using the approach of Degenhardt and colleagues, we applied a multiplier (Box) derived from a more contemporary (late 2009 into 2010) survey of methamphetamine users5 to Victorian client-level specialist drug treatment data for the 2013–14 financial year. Figures were then adjusted by Australian population estimates, and the multiplier 95% confidence interval was used to generate a range. This produced estimates of 67 250 regular (range, 50 312–91 635) and 43 232 dependent (range, 34 477–57 947) methamphetamine users for Australia in 2013–14.
By using a contemporary multiplier, our results are a significant advance on those previously published, providing alternate estimates of regular and dependent methamphetamine use in Australia in 2013–14. They suggest that the previously published figures overstate the extent of regular and dependent methamphetamine use by a large margin (by a factor between three and four times). Accurate estimates are important given the sensitivity of the figures (and possible implications) in light of current — and substantial — media and political focus on methamphetamine in Australia, and broader public concern about the perceived threat of methamphetamine use. Nevertheless, while our use of a contemporary multiplier means that our estimates may be more robust than those previously published, caution is needed when interpreting the results of drug use prevalence estimation, particularly those based on multipliers.1
Box – Description of data source and multiplier used in estimating regular and dependent methamphetamine use
Data source |
Data type |
Data manipulation |
Multiplier source |
Multiplier regular use (95% CI) |
Multiplier dependent use (95% CI) |
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Victorian Department of Health and Human Services, Alcohol and Drug Information System |
Clients of specialist drug treatment services (Victoria); 6-monthly |
Multiplication for each half year, divided by two (converting to annual averages), adjusted by Australian Estimated Resident Population (aged 15 years and over) |
Melbourne survey 2010,5 n = 255 |
5.6 (4.2–7.6) |
3.6 (2.6–4.9) |
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Competing interests
Dietze has received funding from Gilead Sciences, Inc. and Reckitt Benckiser for work unrelated to this study, and he is the recipient of a National Health and Medical Research Council Senior Research Fellowship. Quinn is the recipient of a Fulbright Scholarship. The Burnet Institute has received funding through the Victorian Government Operational Infrastructure Scheme. These funders were not involved in the work.
Acknowledgements
We thank the Victorian Department of Health and Human Services for providing Victorian treatment data from the Alcohol and Drug Information System. We also thank Rebecca Jenkinson, Nick Scott, Jenny Chalmers and John Fitzgerald for their input as authors of previous versions of this submission.
References
- Kraus L, Augustin R, Frischer M, et al. Estimating prevalence of problem drug use at national level in countries of the European Union and Norway. Addiction 2003; 98: 471-485.
- Degenhardt L, Larney S, Chan G, et al. Estimating the number of regular and dependent methamphetamine users in Australia, 2002–2014. Med J Aust 2016; 204: 153.
- McKetin R, McLaren J, Kelly E, et al. Estimating the number of regular and dependent methamphetamine users in Australia. Technical Report No. 230. Sydney: National Drug and Alcohol Research Centre; 2005.
- Scott N, Caulkins JP, Ritter A, et al. High-frequency drug purity and price series as tools for explaining drug trends and harms in Victoria, Australia. Addiction 2015; 110: 120-128.
- Quinn B, Stoove M, Papanastasiou C, Dietze P. Methamphetamine use in Melbourne, Australia: baseline characteristics of a prospective methamphetamine-using cohort and correlates of methamphetamine dependence. J Substance Use 2013; 18: 349-362.