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Keywords:

  • Amphetamine;
  • longitudinal;
  • methamphetamine;
  • outcomes;
  • psychiatric comorbidity;
  • substance abuse;
  • treatment;
  • HIV risk;
  • crime

Abstract

Aims

To evaluate the impact of community-based drug treatment on methamphetamine use using inverse probability 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 detoxification (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.