Evaluating the impact of community-based treatment options on methamphetamine use: findings from the Methamphetamine Treatment Evaluation Study (MATES) Rebecca McKetin 1,2 , Jake M. Najman 3 , Amanda L. Baker 4 , Dan I. Lubman 5 , Sharon Dawe 6 , Robert Ali 7 , Nicole K. Lee 8,9 , Richard P. Mattick 2 & Abdullah Mamun 3 Centre for Research on Ageing, Health and Wellbeing, The Australian National University, Canberra, Australia, 1 National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia, 2 Queensland Alcohol and Drug Research and Education Centre, University of Queensland, Brisbane, Australia, 3 Centre for Brain and Mental Health Research, University of Newcastle, Newcastle, Australia, 4 Turning Point Alcohol and Drug Centre, Eastern Health and Monash University, Melbourne, Australia, 5 School of Psychology, Griffith University, Brisbane, Australia, 6 University of Adelaide, Adelaide, Australia, 7 The National Centre for Education and Training on Addiction, Flinders University, Adelaide, Australia 8 and National Drug Research Institute, Curtin University, Perth, Australia 9 ABSTRACT Aims To evaluate the impact of community-based drug treatment on methamphetamine use using inverse probabil- ity of treatment-weighted (IPTW) estimators to derive treatment effects. Design A longitudinal prospective cohort study with follow-ups at 3 months, 1 year and 3 years. Treatment effects were derived by comparing groups at follow-up. IPTW estimators were used to adjust for pre-treatment differences between groups. Setting Sydney and Brisbane, Australia. Participants Participants were methamphetamine users entering community-based detoxifica- tion (n = 112) or residential rehabilitation (n = 248) services and a quasi-control group of methamphetamine users (n = 101) recruited from the community. Measurements Frequency of methamphetamine use between interviews (no use, less than weekly, 1–2 days per week, 3+ days per week), continuous abstinence from methamphetamine use, past month methamphetamine use and methamphetamine dependence. Findings Detoxification did not reduce methamphetamine use at any follow-up relative to the quasi-control group. Relative to quasi-control and detoxification groups combined, residential rehabilitation produced large reductions in the frequency of methamphetamine use at 3 months [odds ratio (OR) = 0.23, 95% confidence interval (CI) 0.15–0.36, P < 0.001), with a marked attenuation of this effect at 1 year (OR 0.62, 95% CI 0.40–0.97, P = 0.038) and 3 years (OR = 0.71, 95% CI 0.42–1.19, P = 0.189). The greatest impact was for abstinence: for every 100 residential rehabilitation clients there was a gain of 33 being continuously abstinent at 3 months, with this falling to 14 at 1 year and 6 at 3 years. Conclusions Community-based residential rehabilitation may produce a time-limited decrease in methamphetamine use, while detoxification alone does not appear to do so. Keywords Amphetamine, longitudinal, methamphetamine, outcomes, psychiatric comorbidity, substance abuse, treatment, HIV risk, crime. Correspondence to: Rebecca McKetin, Centre for Mental Health Research, ANU College of Medicine, Biology and Environment,The Australian National University, Canberra, ACT 0200, Australia. E-mail: rebecca.mcketin@anu.edu.au Submitted 23 November 2011; initial review completed 5 January 2012; final version accepted 2 May 2012 INTRODUCTION Methamphetamine dependence is estimated to cost at least three-quarters as much as heroin dependence per person [1], yet there is comparatively little evidence documenting treatment outcomes [2] and few specia- lized treatment options [3]. Notable is the lack of any evaluation of whether generic community-based drug treatment can reduce methamphetamine dependence. Existing studies in this area focus largely on opioids and/or alcohol [4–6]—this research finding support for community-based residential rehabilitation [4–6] but less for detoxification [4]. However, these findings may not apply to people who are dependent on methampheta- RESEARCH REPORT doi:10.1111/j.1360-0443.2012.03933.x © 2012 The Authors. Addiction © 2012 Society for the Study of Addiction Addiction, 107, 1998–2008