The present study had two main findings. First, this study provides novel evidence that the amount of time that participants attended the workplace during an induction period predicts cocaine abstinence outcomes under the employment-based abstinence reinforcement intervention. Second, this study provides a systematic replication of prior research that employment-based abstinence reinforcement can increase cocaine abstinence.
This study provides novel evidence, not shown in prior research, that the amount of workplace attendance during an induction period, in which participants were allowed to work independent of their urinalysis results, predicted cocaine abstinence outcomes under the employment-based abstinence reinforcement intervention. Although the descriptive nature of this result does not allow for definitive conclusions, these results have potential practical and theoretical implications that are worthy of further investigation.
Practically, these results suggest that employment-based abstinence reinforcement may be most effective if each participant's workplace attendance could be increased before imposing the abstinence reinforcement contingency. Increasing the reinforcement for attendance or changing the types of work to meet each participant's interests are two potential ways to increase attendance. Future studies could investigate methods to increase attendance. Once methods of increasing workplace attendance are established, then research could be conducted to determine if exposing participants to interventions that increase their attendance could increase their subsequent response to employment-based abstinence reinforcement.
Second, the data from this study, in combination with data from prior studies, suggest that there are some circumstances in which employment-based abstinence reinforcement should not be arranged. Like other abstinence reinforcement interventions, employment-based abstinence reinforcement has not been effective in all participants (e.g., Silverman et al., 2007
). Unfortunately, arranging employment-based abstinence reinforcement in nonresponsive individuals can have the undesirable effect of dramatically reducing (Silverman et al., 2007
) or even ending (Knealing et al., 2006
) their workplace participation. The data from the current study suggest that we may be able to identify some of those potentially nonresponsive individuals prior to arranging the employment-based reinforcement contingency by examining their rates of attendance during an induction period similar to the period used in this study. In the current study, for example, participants who attended less than 40% of the available minutes during the induction period were not likely to achieve sustained cocaine abstinence in the intervention period (). Because imposing an employment-based abstinence reinforcement contingency with those individuals may also have the undesirable effect of reducing or ending their workplace participation (e.g., see ), it may be therapeutically counterproductive to initiate an employment-based abstinence reinforcement contingency for those individuals, at least as long as their induction period attendance remains low.
Theoretically, the data from this study, in combination with basic research on reinforcement (Premack, 1961
), suggest that induction-period measures of attendance provide a measure of the reinforcing value of the employment for individual participants. Prior research on reinforcement has shown that the amount that an organism engages in a behavior when given relatively unconstrained opportunity is related to the likelihood that access to that behavior will serve as a reinforcer when offered in the context of a reinforcement contingency (Premack, 1961
). This principle has been applied to identify potential reinforcers for children with developmental delays or autism and in other applied contexts (e.g., Hagopian, Rush, Lewin, & Long, 2001
), but it has not been used to identify reinforcers that could be used to reinforce drug abstinence in contingency management interventions. Prior studies have attempted to identify potential reinforcers that could be used in contingency management interventions for drug abuse treatment populations; however, those studies have relied exclusively on patient ratings of a range of potential reinforcers presented in reinforcer surveys (Amass, Bickel, Crean, Higgins, & Badger, 1996
; Chutuape, Silverman, & Stitzer, 1998
; Schmitz, Rhoades, & Grabowski, 1994
). Furthermore, those studies did not evaluate whether the results of the reinforcer survey predicted actual reinforcement effects.
The demonstration of the effectiveness of the employment-based abstinence reinforcement intervention is particularly noteworthy because of the population that was the focus of this study. Participants were unemployed adults who were receiving welfare benefits and methadone treatment in community methadone treatment programs. Despite the fact that these individuals were engaged both in community drug abuse treatment and in the social service system, they continued to use cocaine persistently and remained unemployed. This population is in desperate need of effective interventions to address both their persistent cocaine use and their unemployment. Our results provided a systematic replication of results obtained in a prior study (Silverman et al., 2007
) that showed that employment-based abstinence reinforcement could increase cocaine abstinence in a similar population of unemployed injection drug users who also persisted in using cocaine during community methadone treatment. This replication is particularly important because participants in the current study shared characteristics with participants in a prior study by Knealing et al. (2006)
that failed to show a clear and significant effect of employment-based abstinence reinforcement. Participants in all three of the recent studies (Knealing et al.; Silverman et al., 2007
; and the present study) were enrolled in community methadone treatment programs and used cocaine persistently during methadone treatment. However, like participants in the study by Knealing et al. and unlike the study by Silverman et al., the participants in the current study had to be receiving welfare benefits to be eligible to participate. The failure of employment-based abstinence reinforcement in the study by Knealing et al. could have resulted from the fact that the welfare benefits received by participants in that study provided an alternative source of income, which may have diminished the effectiveness of abstinence reinforcement intervention (see discussion
of open and closed economies in Hursh, 1980
). The current study shows that employment-based abstinence reinforcement can be effective in adults who are receiving welfare benefits.
The study employed a multiple baseline design across drugs (cocaine and opiates), which was compromised because opiate abstinence was very high in this population and could not be increased further with the employment-based abstinence reinforcement intervention. Nevertheless, two aspects of the study design provided sound evidence that the employment-based abstinence reinforcement intervention did increase cocaine abstinence. First, cocaine abstinence was extremely stable prior to the introduction of the intervention and increased abruptly (, , and ) and significantly () after its introduction. Second, because participants were enrolled in the study gradually over a 3-year period (from October, 2003, to March, 2006), the introduction of the abstinence reinforcement contingency was staggered across calendar days, which reduced the chance that some kind of public or unknown event (e.g., a change in drug laws or a change in the availability of cocaine) caused the abrupt change in cocaine abstinence. To provide further evidence that the intervention produced the increase in cocaine abstinence, as opposed to some major uncontrolled and unknown event, we conducted a secondary analysis of two sequential cohorts of participants within the total sample who were enrolled in separate waves of recruitment. Indeed, both cohorts showed very similar results as the total sample. In both cohorts, rates of cocaine abstinence were extremely stable during the period before the introduction of the cocaine abstinence reinforcement contingency and then increased abruptly immediately after the introduction of the contingency ( and ). Even though this is an unorthodox experimental design, given the large numbers of participants in the separate cohorts and the total sample and the remarkably clear results within each cohort and the total sample, it seems clear that the employment-based abstinence reinforcement contingency produced the increase in cocaine abstinence. Alternative explanations would be very strained.
One limitation of this study is that there was no control group for comparison, and as described above, there was an unorthodox within-participant experimental design (i.e., staggered introduction of the abstinence contingency over calendar days across participants and across cohorts of participants). Without a control group or a more rigorous within-participant experimental design, we cannot be certain that the employment-based abstinence reinforcement intervention produced the change in cocaine abstinence observed in the intervention period. Furthermore, without a control group that was not exposed to the intervention, we cannot know for certain the extent to which the measures of induction-period attendance predicted the outcome of a reinforcement contingency (i.e., employment-based reinforcement of cocaine abstinence) or whether those induction-period measures are simply marker variables that are associated with subsequent higher rates of cocaine abstinence, which would have been evident even if participants had not been exposed to the employment-based abstinence reinforcement contingency. This potential alternative explanation could be examined in a future experiment that conducts similar correlation and multiple regression analyses in participants who, after a similar workplace induction period, are randomly assigned to receive or not to receive exposure to an employment-based abstinence reinforcement contingency. If attendance during the workplace induction period predicts cocaine abstinence only in participants subsequently exposed to an employment-based abstinence reinforcement intervention, that would provide stronger support for the interpretations proposed in this paper.
Virtually all abstinence reinforcement interventions that have been evaluated in controlled studies have shown that not all individuals respond to the interventions. In most or all instances, fixed quantities of the scheduled reinforcers are used, and efforts have not been made to determine the extent to which the reinforcing value of those putative reinforcers varies across individuals. As suggested by the data in the current study, using employment as a reinforcer in an abstinence reinforcement intervention appears to offer a unique opportunity to assess the value of the reinforcer for each individual prior to implementation of the contingency. Such reinforcer assessments may allow employers in therapeutically oriented workplaces to manipulate parameters of the employment conditions to increase the reinforcing value of employment for each individual and thereby increase the effectiveness of employment-based abstinence reinforcement contingencies for those individuals.