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NDARC Technical Report No. 312 (2010)
Background and aims
Australia has the highest rate of methamphetamine use worldwide, including a substantial population of dependent injecting methamphetamine users. Effective treatment options for methamphetamine dependence are extremely limited, yet over 16,000 Australians present to drug treatment services with methamphetamine use problems each year. In 2006 the Methamphetamine Treatment Evaluation Study (MATES) was established to determine whether existing drug treatment approaches reduced methamphetamine use and related harms. MATES is a prospective longitudinal study of methamphetamine users entering community-based drug treatment services and a non-treatment comparison group. The cohort was from Sydney and Brisbane in 2006/2007 and has been followed-up at three months and 12 months post-treatment. The outcomes from MATES have been extremely positive so far, with significant reductions in methamphetamine use and related harms being seen after drug treatment (Cogger et al., 2008; McKetin et al., 2009).
The aim of the current study was to conduct a three year follow-up of the MATES cohort to establish the longer-term treatment outcomes for methamphetamine
dependence. From this study we hoped to learn:
what proportion of methamphetamine users show reductions in methamphetamine use and related harms three years after starting drug treatment
how many methamphetamine users return to drug treatment during this time frame, and
what types of drug treatment, and client characteristics, are associated with the best long-term outcomes for methamphetamine dependence.
The findings presented in this report pertain to the Sydney arm of the cohort only.
Methamphetamine treatment entrants (N = 300) were recruited from 26 drug treatment services in Sydney and the surrounding regions during 2006/07. Treatment services were chosen from the National Minimum Data Set for Alcohol and Other Drug Treatment Services (NMDS-AODTS). The non-treatment comparison group (n = 101) were dependent methamphetamine users who were recruited through various community health services and needle and syringe programs from the same geographic region as the treatment group and during the same time frame.
Participants had previously been interviewed on entry to drug treatment (or on entry to the study, in the case on the non-treatment group) and again 3 months and 12 months after their baseline interview. The current study involved re-contacting participants and completing a three year follow-up interview. Interviews took approximately 45 minutes and were conducted by phone. Participants were volunteers who completed informed consent and were reimbursed $40.The interview assessed demographic characteristics, drug use and psychiatric status using the Opiate Treatment Index, the Composite International Diagnostic Interview (CIDI), the Brief Psychiatric Rating Scale and the Kessler-10. Treatment exposure measures included treatment duration, modality of treatment (detoxification, residential rehabilitation, counselling), treatment retention and treatment completion. The treatment outcomes of interest were:
methamphetamine dependence and use/abstinence
sexual and injecting risk behaviour
psychotic symptoms and hostility
re-entry to drug treatment.
These outcomes were compared pre- and post-treatment. Further analyses were performed examining treatment outcomes according to whether participants: (a) reentered drug treatment during the follow-up period; (b) did not re-enter drug treatment and were not dependent on methamphetamine at follow-up; and (c) did not re-enter drug treatment but were dependent on methamphetamine at follow-up.
Treatment success was defined as not being dependent on methamphetamine at followup and not having returned to drug treatment. Treatment effects were established using propensity adjusted logistic regression models that compared treatment outcome by baseline treatment exposure. Sensitivity analysis was used to assess the potential impact of attrition on treatment effects.
Characteristics of the sample
Sixty-seven per cent of the original cohort (n = 267) was interviewed at the three-year follow-up and a further 10% were deceased or incarcerated (i.e., 23% were uncontactable or had withdrawn from the study). Of the participants interviewed at three year followup, 71 (27%) were in the non-treatment group and 196 (73%) were treatment participants. Treatment participants had initially received residential rehabilitation (n =126), counselling (n = 19) or detoxification (n = 51) as their main form of drug treatment. The median duration of treatment received was 35 days (range 1 to 190), being longer for residential rehabilitation and counselling than for detoxification (median of 54 and 71 days respectively vs. 5 days). On entry to the study, these participants were dependent on methamphetamine (97%), the majority injected the drug (73%), and their polydrug use consisted mainly of tobacco, cannabis and alcohol, with a notable minority also using heroin (26% in the past month). They had high levels of psychiatric comorbidity, this picture being dominated by depression and psychotic symptoms.
There were significant reductions in methamphetamine use at follow-up in both the treatment and the non-treatment groups. These reductions in harms were apparent at the three month follow-up and persisted until three years after treatment. Reductions in methamphetamine use and related harms in the treatment group were greater than in the non-treatment comparison group at three years post-treatment, but these effects were largely attributable to treatment re-entry. At the three year follow-up:
53% of treatment participants had re-entered drug treatment (cf. 31% in the nontreatment group);
34% had remitted from dependence without any further drug treatment; and
13% were dependent on methamphetamine but had not returned to drug treatment.
The proportion of treatment entrants who remitted from methamphetamine dependence without any further drug treatment was significantly higher than for the non-treatment group at three months (59 vs. 44%, p = 0.017) but not at one year (42 vs. 47% ) or three years (41 vs. 39%) after starting drug treatment.
Long-term treatment success was more common with longer treatment duration and the more intensive treatment modalities of counselling and residential rehabilitation (compared to detoxification). Participants who did poorly were using methamphetamine more often prior to treatment entry, injecting the drug, and they were more likely to be experiencing psychotic symptoms and high levels of psychological distress.
Methamphetamine treatment entrants showed sustained reductions in methamphetamine use and related harms after drug treatment, but these positive outcomes were largely due to ongoing treatment exposure. The single baseline episode of drug treatment examined in this study was found to have short-term benefits, but no long-term benefit compared to a non-treatment comparison group (in terms of recovery from methamphetamine dependence without further treatment exposure). Particularly poor outcomes were observed for heavier injecting methamphetamine users and those with psychotic symptoms and high levels of psychological distress on entry to treatment. On the other hand, around one-third of methamphetamine users recovered without further drug treatment. Positive outcomes were associated with longer and more intensive treatment programs. These findings highlight the chronic and relapsing nature of methamphetamine dependence for a large proportion of methamphetamine users, and a need for a more intensive and sustained treatment approach for this population, with a particular emphasis on follow-up care and relapse prevention.
Rebecca McKetin, Rachel Sutherland, Joanne Ross, Jake Najman, A. Mamun, Amanda Baker, Richard Mattick, Julia Rosenfeld