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Estimating the number of regular and dependent methamphetamine users in Australia, 2002–2014

Louisa Degenhardt, Sarah Larney, Gary Chan, Timothy Dobbins, Megan Weier, Amanda Roxburgh, Wayne D Hall and Rebecca McKetin
Med J Aust 2016; 204 (4): 153. || doi: 10.5694/mja15.00671

Summary

Objective: To estimate the number of regular and dependent methamphetamine users in Australia.

Design: Indirect prevalence estimates were made for each year from 2002–03 to 2013–14. We applied multiplier methods to data on treatment episodes for amphetamines (eg, counselling, rehabilitation, detoxification) and amphetamine-related hospitalisations to estimate the numbers of regular (at least monthly) and dependent methamphetamine users for each year. Dependent users comprised a subgroup of those who used the drug regularly, so that estimates of the sizes of these two populations were not additive.

Results: We estimated that during 2013–14 there were 268 000 regular methamphetamine users (95% CI, 187 000–385 000) and 160 000 dependent users (95% CI, 110 000–232 000) aged 15–54 years in Australia. This equated to population rates of 2.09% (95% CI, 1.45–3.00%) for regular and 1.24% (95% CI, 0.85–1.81%) for dependent use. The rate of dependent use had increased since 2009–10 (when the rate was estimated to be 0.74%), and was higher than the previous peak (1.22% in 2006–07). The highest rates were consistently among those aged 25–34 years, in whom the rate of dependent use during 2012–2013 was estimated to be 1.50% (95% CI, 1.05–2.22%). There had also been an increase in the rate of dependent use among those aged 15–24 years (in 2012–13 reaching 1.14%; 95% CI, 0.80–1.69%).

Conclusions: There have been increases over the past 12 years in the numbers of regular and dependent methamphetamine users in Australia. Our estimates suggest that the most recent numbers are the highest for this period, and that the increase has been most marked among young adults (those aged 15–34 years).

Implications: There is an increasing need for health services to engage with people who have developed problems related to their methamphetamine use.

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  • Louisa Degenhardt1
  • Sarah Larney1
  • Gary Chan2
  • Timothy Dobbins1
  • Megan Weier2
  • Amanda Roxburgh1
  • Wayne D Hall2,3
  • Rebecca McKetin4

  • 1 National Drug and Alcohol Research Centre, UNSW Australia, Sydney, NSW
  • 2 Centre for Youth Substance Abuse Research, University of Queensland, Brisbane, QLD
  • 3 National Addiction Centre, Institute of Psychiatry, Psychology and Neuroscience, Kings College London, London, UK
  • 4 National Drug Research Institute, Curtin University, Perth, WA

Correspondence: l.degenhardt@unsw.edu.au

Acknowledgements: 

Sarah Larney and Louisa Degenhardt are supported by fellowships from the National Health and Medical Research Council (grant numbers 1035149 and 1041472 respectively). The National Drug and Alcohol Research Centre at the University of New South Wales is supported by funding from the Australian Government under the Substance Misuse Prevention and Service Improvements Grant Fund. We thank Richard P. Mattick for comments on a draft of this paper.

Competing interests:

No relevant disclosures.

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access_time 09:04, 1 March 2016
Thomas Vandyk

The estimates on the use of methamphetamines for the current study were based on treatment admission rates from a cohort of Sydney based methamphetamine users from 2003. While this methodology has been widely used internationally, its effectiveness is dependent on the extent to which the cohort accurately reflects drug use for the wider population. Unfortunately, the use of data from the 2003 fails to account for the significant shifts in the consumption of methamphetamine over the subsequent decade. From 2010 to 2013, the purity of ice increased from an average of 21% to 64% while the purity of speed shifted from 12% to 37%.

The research also failed to identify that over the same time period the proportion of people using the drug on a weekly or daily basis has increased from 9% to 15% of users according to the NDSHS survey.

Based on current estimates, an equivalent cohort would be using a far more pure form of methamphetamine with greater frequency.

That many individuals are using higher purity methamphetamine on a weekly or daily basis almost certainly accounts for a significant proportion of the increase in drug-related harms. The use of data from a 2003 cohort and the failure to account for the shifts in the drug market that have occurred appears to be both misleading and inappropriate.

Competing Interests: No relevant disclosures

Mr Thomas Vandyk
University of Melbourne

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