A Meta-Analytic Examination of Drug Treatment Courts: Do They Reduce Recidivism?

2. Method

Similar to traditional quantitative research methods, the meta-analytic process involves three basic steps:

1. literature review –
identifying and gathering relevant research studies;
2. data collection –
xtracting data through pre-determined coding procedures; and
3. data analysis –
analyzing the aggregated data using statistical techniques.

To gather eligible studies for the meta-analysis, a comprehensive search was conducted of the literature over the last 20 years including unpublished doctoral theses and governmental reports. A secondary search was conducted using the bibliographies of the relevant literature, prior meta-analyses and the Internet. An explicit set of criteria was established in order for a study to be included in the analysis:

  1. the study examined the effectiveness of a drug treatment court (i.e., an intervention that involved both a court monitored component and a substance abuse treatment component) for offenders charged with a criminal offence;
  2. the study used a control group or comparison group that did not experience the drug treatment court (or provided sufficient pre/post data);
  3. sufficient statistical information was reported in order to extract an effect size; and,
  4. the study measured the impact of the DTC on recidivism rates.

Standardized information was drawn from each accepted study using a pre-designed coding manual. In accordance with standard meta-analytic techniques, multiple definitions of recidivism were accepted. For example, recidivism was defined as a new conviction or simply a new charge. It was not, however, defined as a relapse on the substance of choice – only new criminal behaviour was coded as recidivism. In order to generate sufficient data for analysis, several coding techniques were used. For example, if 70% or more of the study sample were first-time offenders, it was coded as a "primarily first-time offender program." In addition, several variables were coded only if the authors made an explicit positive statement. For example, the use of methadone was only coded as "yes" if the authors directly stated this to be a fact. Therefore, the comparisons made in this report are subject to this limitation. It should be noted, however, that this is a general issue within all meta-analyses.

In accordance with the meta-analytic techniques of Rosenthal (1991), the phi coefficient (Pearson’s r product moment correlation applied to dichotomous data) was used as the effect size estimate. In cases where multiple control groups were used in a single study, the results were combined in order to generate a single ESE for each program in order to avoid skewing the results by double counting programs. In addition, where multiple follow-up periods were reported in a single study, the longer period was selected.

Once the ESE from each study was calculated for recidivism, the overall mean effect size estimate, along with the corresponding confidence intervals, and a weighted effect size estimate were calculated. Additional analyses were also conducted to explore whether certain variables had a moderating impact on ESE magnitude where adequate information was available. For example, the effect of DTC participation was analyzed based upon the length of the programs or the criminal history of the offenders within the programs.

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