Outcomes over the treatment period were measured in several ways: (1) Total abstinence from methamphetamine was assessed by the mean number of metabolite-free urine samples provided; (2) continuous abstinence was measured as the longest period of uninterrupted abstinence as measured using urine samples (number of tests); (3) the ability to initiate abstinence from methamphetamine was defined as the mean number of tests that occurred in each condition prior to producing the first methamphetamine-negative test result; (4) the ability to protect against relapse following a period of abstinence was assessed by counting the number of participants who relapsed following a 4-week period of abstinence, which, in our opinion, is a clinically significant period of abstinence.
The main effect of schedules for producing differences in abstinence outcomes was tested using analysis of variance.
One-way ANOVA indicated that there were significant between-group differences, F(4, 78) = 4.590, p < 0.05, in the relative efficacy of the schedules for initiating abstinence. Tukey-Kramer multiple comparison tests revealed the significant differences were between Schedule 5 and Schedules 1 and 3, with Schedule 5 initiating abstinence quicker than the other two (q = 4.492; q = 5.241, respectively).
Analyses showed that approximately half as many individuals in the group receiving reinforcement according to Schedule 1 obtained a 4-week period of abstinence relative to the other four reinforcement schedules (see Figure 4).
First, it appears that the schedule developed by Higgins and colleagues (Schedule 5) is generally superior to those to which we compared it in terms of initiating abstinence and preventing relapse when delivered in the context of thrice weekly drug abuse counseling groups.
For instance Roll and colleagues (e.g., Roll & Higgins, 2000; Roll et al., 1996) previously examined the relative contributions of reinforcer escalation and reset contingencies in initiating and maintaining abstinence. This was accomplished by comparing schedules that were systematically varied in order to isolate the relative contributions of specific components of the schedules.
Although this study was not designed to isolate schedule components, or to assess their relative contributions to the initiation and maintenance of abstinence, it does permit some comments on the topic.
With regards to the maintenance of abstinence the present results suggest that schedules which combine escalating reinforcer magnitude with reset contingencies (Schedule 5) are more likely to protect against relapse following a period of abstinence than any of the other scheduling arrangements investigated.
The only difference was the manner in which the reinforcers were scheduled, yet statistically significant differences were observed between the schedules in terms of their ability to both initiate and maintain abstinence. Based on available data it appears that using the escalating schedule of reinforcement with a reset contingency for use developed by Higgins (Higgins, Budney, et al., 1994) provides the best chance for a successful substance abuse treatment episode.
Voucher-based reinforcement of opiate plus cocaine abstinence in treatment-resistant methadone patients: Effects of reinforcer magnitude.
Initial abstinence and success in achieving longer term cocaine abstinence.