Long-Term Effects of Incentives for HIV Viral Suppression: A Randomized Clinical Trial.

Achieving viral suppression in people living with HIV improves their quality of life and can help end the HIV/AIDS epidemic. However, few interventions have successfully promoted HIV viral suppression. The purpose of this study was to evaluate the long-term effectiveness of financial incentives for viral suppression in people living with HIV. People living with a detectable HIV viral load (≥ 200 copies/mL) were randomly assigned to Usual Care (n = 50) or Incentive (n = 52) groups. Incentive participants earned up to $10 per day for providing blood samples with an undetectable or reduced viral load. During the 2-year intervention period, the percentage of blood samples with a suppressed viral load was significantly higher among Incentive participants (70%) than Usual Care participants (43%) (OR = 7.1, 95% CI 2.7 to 18.8, p < .001). This effect did not maintain after incentives were discontinued. These findings suggest that frequent delivery of large-magnitude financial incentives for viral suppression can produce large and long-lasting improvements in viral load in people living with HIV. ClinicalTrials.gov Identifier: NCT02363387.

Abstinence-contingent wage supplements for adults experiencing homelessness and alcohol use disorder: A randomized clinical trial.

This study evaluated the effectiveness of abstinence-contingent wage supplements in promoting alcohol abstinence and employment in adults experiencing homelessness and alcohol use disorder. A randomized clinical trial was conducted from 2019 to 2022. After a 1-month Induction period, 119 participants were randomly assigned to a Usual Care Control group (n = 57) or an Abstinence-Contingent Wage Supplement group (n = 62). Usual Care participants were offered counseling and referrals to employment and treatment programs. Abstinence-Contingent Wage Supplement participants could earn stipends for working with an employment specialist and wage supplements for working in a community job but had to maintain abstinence from alcohol as determined by transdermal alcohol concentration monitoring devices to maximize pay. Abstinence-Contingent Wage Supplement participants reported significantly higher rates of alcohol abstinence than Usual Care participants during the 6-month intervention (82.8% vs. 60.2% of months, OR = 3.4, 95% CI 1.8 to 6.3, p < .001). Abstinence-Contingent Wage Supplement participants were also significantly more likely to obtain employment (51.3% vs. 31.6% of months, OR = 2.6, 95% CI 1.5 to 4.4, p < .001) and live out of poverty (38.2% vs. 16.7% of months, OR = 3.7, 95% CI 2.0 to 7.1, p < .001) than Usual Care participants. These findings suggest that Abstinence-Contingent Wage Supplements can promote alcohol abstinence and employment in adults experiencing homelessness and alcohol use disorder. ClinicalTrials.gov Identifier: NCT03519009.

Rich-lean transitions produced by stimuli associated with accurate and inaccurate responding by pigeons.

Discriminable transitions from relatively favorable schedules of reinforcement to unfavorable schedules (rich-lean transitions) can produce disruptions in operant behavior. A prior evaluation in our laboratory (Toegel et al., 2021) found that placing a border around a key displayed on a resistive touchscreen increased pigeons' response accuracy relative to conditions without the border. We sought to evaluate (a) whether effects of the key border on accuracy could be replicated in a within-session comparison and (b) whether transitions from a response alternative associated with accurate responding to one associated with inaccurate responding functioned as rich-lean transitions. Pigeons' key pecks were reinforced according to a two-component multiple schedule with identical fixed-ratio (FR) requirements and reinforcer magnitudes. The components differed based on whether the virtual key was displayed behind a border or with no border. In line with prior research, within-session comparisons yielded higher response accuracy in components with the key border than in components without the border. Furthermore, transitions from the border component to the no border component functioned as rich-lean transitions for pigeons whose obtained FRs in no border components were substantially larger than the FR programmed in that component.

Cost and cost-effectiveness of abstinence contingent wage supplements.

BACKGROUND: Substance use disorders are correlated with unemployment and poverty. However, few interventions aim to improve substance use, unemployment, and, distally, poverty. The Abstinence-Contingent Wage Supplement (ACWS) randomized controlled trial combined a therapeutic workplace with abstinence-contingent wage supplements to address substance use and unemployment. The ACWS study found that abstinence-contingent wage supplements increased the percentage of participants who had negative drug tests, who were employed, and who were above the poverty line during the intervention period. This study presents the cost of ACWS and calculates the cost-effectiveness of ACWS compared with usual care. METHODS: To calculate the cost and cost-effectiveness of ACWS, we used activity-based costing methods to cost the intervention and calculated the costs from the provider and healthcare sector perspective. We calculated incremental cost-effectiveness ratios and cost-effectiveness acceptability curves for negative drug tests and employment. RESULTS: ACWS cost $11,310 per participant over the 12-month intervention period. Total intervention and healthcare costs per participant over the intervention period were $20,625 for usual care and $30,686 for ACWS. At the end of the intervention period an additional participant with a negative drug test cost $1437 while an additional participant employed cost $915. CONCLUSIONS: ACWS increases drug abstinence and employment and may be cost-effective at the end of the 12-month intervention period if decision makers are willing to pay the incremental cost associated with the intervention.

Latent factor structure of behavioral economic heroin and cocaine demand curves.

Research has shown that behavioral economic demand curve indices can be characterized by a two-factor latent structure and that these factors can predict dimensions of substance use. No study to date has examined the latent factor structure of heroin and cocaine demand curves. The objective of this study was to use exploratory factor analysis to examine the underlying factor structure of the facets of heroin and cocaine reinforcement derived from heroin and cocaine demand curves. Participants were 143 patients from two samples that met the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5; American Psychiatric Association [APA], 2013) criteria for opioid dependance and were undergoing medication-assisted treatment (methadone or buprenorphine). Heroin and cocaine demand curves were generated via hypothetical purchase tasks (HPT) that assessed consumption at 9 or 17 levels of prices from $0 to $500. Five facets of demand were generated from the tasks (Q0, 1/α, Pmax, Omax, and break point). Principal components analysis was used to examine the latent structure among the variables. The results revealed a two-factor solution for both heroin and cocaine demand. These factors were interpreted as persistence, consisting of 1/α, Pmax, Omax, and break point, and amplitude, consisting of Q0 and Omax, and in one case, 1/α. Heroin factors had some predictive power for future substance use, but cocaine factors did not. These findings suggest that heroin and cocaine demand indices can be reduced to two factors indicating sensitivity and volume of consumption, and that these factors may be able to predict substance use for heroin. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Being at work improves stress, craving, and mood for people with opioid use disorder: Ecological momentary assessment during a randomized trial of experimental employment in a contingency-management-based therapeutic workplace.

Employment problems are common among people with substance use disorders (SUDs), and improving vocational functioning is an important aspect of SUD treatment. More detailed understanding of the psychosocial benefits of employment may help refine vocational interventions for people with SUDs. Here, we used ecological momentary assessment to measure possible affective improvements associated with work. Participants (n = 161) with opioid use disorder were randomized to work (job-skills training) in a contingency-management-based Therapeutic Workplace either immediately or after a waitlist delay. Throughout, participants responded via smartphone to randomly scheduled questionnaires. In linear mixed models comparing responses made at work vs. all other locations, being at work was associated with: less stress, less craving for opioids and cocaine, less negative mood, more positive mood, and more flow-like states. Some of these differences were also observed on workdays vs. non-workdays outside of work hours. These results indicate that benefits associated with work may not be restricted to being actually in the workplace; however, randomization did not reveal clear changes coinciding with the onset of work access. Overall, in contrast to work-associated negative moods measured by experience-sampling in the general population, Therapeutic Workplace participants experienced several types of affective improvements associated with work.

The aversiveness of timeout from response-dependent and response-independent food deliveries as a function of delivery rate.

Seven experiments with rats assessed the aversiveness of timeout using punishment and avoidance procedures. Experiments 1 and 2 considered the contributions of stimulus change, suspending the response-reinforcer contingency, response prevention, the general disruption in the reinforcement schedule during time-in, and overall decreases in reinforcement. Results support the conclusion that response-contingent timeouts punish behavior because they are signaled periods during which an ongoing schedule of positive reinforcement is suspended. Experiments 3, 4, and 5 assessed effects of the reinforcement rate during time-in on the punitive efficacy of timeout and, for comparison, electric shock. Evidence for a direct relation between reinforcement rate and punitive efficacy was equivocal. In Experiments 6 and 7, responding avoided timeout from response-independent food deliveries. Responding was acquired rapidly when it avoided timeouts from free deliveries of pellets or a sucrose solution, but not when it avoided free deliveries of water. At steady-state, avoidance rates and proficiency were directly related to the rate of pellet or sucrose deliveries. The relation between the nature of the time-in environment and the aversiveness of timeout was clear in our avoidance experiments, but not in our punishment experiments. We discuss interpretive problems in evaluating the aversiveness of timeout in the punishment paradigm.

Abstinence-contingent wage supplements to promote drug abstinence and employment: Post-intervention outcomes.

BACKGROUND: Substance use disorder, unemployment, and poverty are interrelated problems that have not been addressed adequately by existing interventions. This study evaluated post-intervention effects of abstinence-contingent wage supplements on drug abstinence and employment. METHODS: Unemployed adults enrolled in opioid agonist treatment were randomly assigned to an abstinence-contingent wage supplement group (n = 44) or a usual care control group (n = 47). All participants could work with an employment specialist throughout a 12-month intervention period. Those in the abstinence-contingent wage supplement group earned stipends for working with the employment specialist and, after gaining employment, abstinence-contingent wage supplements for working in their community job but had to provide opiate- and cocaine-negative urine samples to maximize pay. To assess post-intervention effects of abstinence-contingent wage supplements and compare those effects to during-intervention effects, we analyzed urine samples and self-reports every 3 months during the 12-month intervention and the 12-month post-intervention period. RESULTS: During the intervention, abstinence-contingent wage supplement participants provided significantly more opiate- and cocaine-negative urine samples than usual care control participants; abstinence-contingent wage supplement participants were also significantly more likely to become employed and live out of poverty than usual care participants during intervention. During the post-intervention period, the abstinence-contingent wage supplement and usual care control groups had similar rates of drug abstinence, similar levels of employment, and similar proportions living out of poverty. CONCLUSIONS: Long-term delivery of abstinence-contingent wage supplements can promote drug abstinence and employment, but many patients relapse to drug use and cease employment when wage supplements are discontinued.

Technology-assisted opioid education for out-of-treatment adults with opioid use disorder.

OBJECTIVE: To evaluate the feasibility and potential efficacy of a technology-assisted education program in teaching adults at a high risk of opioid overdose about opioids; opioid overdose; and opioid use disorder medications. METHOD: A within-subject, repeated-measures design was used to evaluate effects of the novel technology-assisted education program. Participants (N = 40) were out-of-treatment adults with opioid use disorder, recruited in Baltimore, Maryland from May 2019 to January 2020. The education program was self-paced and contained three courses. Each course presented information and required answers to multiple-choice questions. The education program was evaluated using a 50-item test, delivered before and after participants completed each course. Tests were divided into three subtests that contained questions from each course. We measured accuracy on each subtest before and after completion of each course and used a mixed-effects model to analyze changes in accuracy across tests. RESULTS: The technology-assisted education program required a median time of 91 min of activity to complete. Most participants completed the program in a single day. Accuracy on each subtest increased only after completion of the course that corresponded to that subtest, and learning comparisons were significant at the p < .001 level for all subtests. Accuracy on each subtest was unchanged before completion of the relevant course, and increases in accuracy were retained across subsequent tests. Learning occurred similarly independent of participant education, employment, and poverty. CONCLUSIONS: Technology-assisted education programs can provide at-risk adults with access to effective education on opioids, opioid overdose, and opioid use disorder medications. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Psychosocial Interventions to Promote Undetectable HIV Viral Loads: A Systematic Review of Randomized Clinical Trials.

Suppressing HIV viral loads to undetectable levels is essential for ending the HIV/AIDS epidemic. We evaluated randomized controlled trials aimed to increase antiretroviral medication adherence and promote undetectable viral loads among people living with HIV through November 22, 2019. We extracted data from 51 eligible interventions and analyzed the results using random effects models to compare intervention effects between groups within each intervention and across interventions. We also evaluated the relation between publication date and treatment effects. Only five interventions increased undetectable viral loads significantly. As a whole, the analyzed interventions were superior to Standard of Care in promoting undetectable viral loads. Interventions published more recently were not more effective in promoting undetectable viral loads. No treatment category consistently produced significant increases in undetectable viral loads. To end the HIV/AIDS epidemic, we should use interventions that can suppress HIV viral loads to undetectable levels.

Effects of advance notice on transition-related pausing in pigeons.

Transitions between tasks can produce behavioral disruptions that are characterized as problematic. Advance notice, a procedure designed to reduce disruptions, involves presenting a stimulus to warn of the end of the ongoing activity and the nature of the upcoming activity. Clinical evaluations of advance notice have produced mixed results. We studied advance notice in a controlled laboratory setting. Pigeons' keypecking was maintained on a multiple schedule with 2 fixed-ratio components. In the lean component, completing the ratio produced brief access to food; in the rich component, completing the ratio produced longer access. Disruptions in operant behavior, measured as pauses in pecking, were reliably produced in the transition from a rich component to a lean one. Advance notice was provided by flashing the houselight before transitions to lean components. Advance notice did not reduce pausing in the rich-lean transition; instead, it tended to increase it. When the flashing houselight warned of a transition but was equally likely to be followed by the rich component as the lean one, the stimulus had no reliable effect on pausing. Despite its limitations as a translational model of clinical settings, this experiment suggests that clinical use of advance notice should be approached with caution.

Design and evaluation of a touchscreen apparatus for operant research with pigeons.

We developed a touchscreen apparatus for pigeons and conducted a series of experiments that assessed its utility for free-operant procedures. The apparatus incorporated an on-board Windows computer, an electromechanical interface, an amplified speaker, and the touchscreen. We found that merely projecting a virtual key on the screen was insufficient; too many pecks missed the key. Adding a visual target in the center of the key and providing visual feedback for on-key pecks both failed to improve response accuracy. Accuracy was improved by imposing a timeout after off-key pecks or providing a physical boundary around the key. With the physical boundary, response accuracy was comparable to that obtained with conventional plastic keys, and response acquisition via autoshaping also was comparable. Mixing the color elements of the screen's pixels produced color stimuli, but the colors did not function as pure wavelengths of light in tests of stimulus generalization. Both colors and geometric shapes functioned as discriminative stimuli in multiple schedules with variable-interval and extinction components or rich and lean fixed-ratio components. In general, our touchscreen apparatus is a viable alternative to conventional pigeon chambers and increases the experimenter's options for visual stimuli, auditory stimuli, and the number and location of response keys.

Factors associated with obtaining employment among opioid use disorder patients enrolled in a therapeutic workplace intervention.

BACKGROUND: Unemployment is a common problem among adults who have substance use disorder that often persists during treatment and recovery. We identified patient characteristics that were associated with obtaining employment among unemployed adults in opioid use disorder treatment. METHODS: This analysis used data from participants (N = 91) who were enrolled in a randomized controlled trial evaluating the effectiveness of a therapeutic workplace in promoting drug abstinence and employment. After a 3-month training period (Phase 1), participants were randomly assigned to a study group and could work for 12 months with an employment specialist who assisted participants in obtaining employment (Phase 2). A logistic regression model was used to identify patient characteristics that were associated with obtaining employment. RESULTS: Of the 91 participants, 39 (42.9 %) obtained employment. Compared to participants who did not obtain employment, participants who obtained employment worked more days in the therapeutic workplace during the training period (Phase 1) [OR (95 % CI) = 1.072 (1.015-1.132), p = .014], provided more opiate- and cocaine-negative urine samples while seeking employment [OR (95 % CI) = 1.015 (1.002-1.027), p = .025], and reported not usually being unemployed at study intake [OR (95 % CI) = 0.229 (0.080-0.652), p = .007]. CONCLUSIONS: Our analyses suggest that among unemployed adults in opioid use disorder treatment, those with the lowest rates of therapeutic workplace attendance, lowest rates of drug abstinence while seeking employment, and relatively long histories of unemployment are the least likely to obtain employment. These relations are potentially addressable at a practical level, and future research could build on these findings to improve the effectiveness of employment-based interventions.

Remotely delivered incentives to promote buprenorphine treatment engagement in out-of-treatment adults with opioid use disorder.

BACKGROUND: Opioid overdose remains a leading cause of death. Office-based buprenorphine could expand access to treatment to the many opioid users who are not in treatment and who are at risk for opioid overdose. However, many people in need of buprenorphine treatment do not enroll in treatment. This randomized pilot trial evaluated efficacy of a remotely delivered incentive intervention in promoting engagement in buprenorphine treatment in out-of-treatment adults with opioid use disorder. METHODS: Participants (N = 41) were offered referrals to buprenorphine treatment and randomly assigned to Control or Incentive groups for 6 months. Incentive participants were offered incentives for enrolling in buprenorphine treatment, verified by providing documentation showing that they received a buprenorphine prescription, and providing videos taking daily buprenorphine doses. Participants used a smartphone application to record and submit a video of their buprenorphine prescription and daily buprenorphine administration. Incentive earnings were added remotely to reloadable credit cards. RESULTS: Incentive participants were significantly more likely to enroll in treatment compared to control participants (71.4 % versus 30.0 % of participants; OR [95 % CI]: 6.24 [1.46-26.72], p = .014). Few participants in either group adhered to buprenorphine treatment, and the two groups continued to use opioids, including fentanyl at high and comparable rates. The two groups did not differ in the percentage of urine samples that were positive for buprenorphine, opiates, fentanyl, or methadone at monthly assessments conducted during the 6-month intervention. CONCLUSIONS: Remotely delivered incentives can connect out-of-treatment adults with opioid use disorder to treatment, but additional supports are needed to promote buprenorphine adherence.

Quality of life during a randomized trial of a therapeutic-workplace intervention for opioid use disorder: Web-based mobile assessments reveal effects of drug abstinence and access to paid work.

Background: Employment and improved quality of life (QOL) are, separately, valued outcomes of substance use disorder (SUD) treatment. It is also important to understand QOL changes caused by employment itself; therefore, we assessed QOL during a randomized trial of a contingency-management-based Therapeutic Workplace for people with opioid use disorder. Methods: For 12 weeks, participants (n = 61) responded to QOL questionnaires in a mobile web app accessed with study-issued smartphones. At enrollment, participants were randomized to work in the Therapeutic Workplace immediately (immediate work group, IWG) or after a 3-week waitlist delay (delayed work group, DWG). Once both groups could work, wage-resetting contingencies were introduced for their opiate- and cocaine-urinalysis. Data were analyzed by (1) access to work with and without contingencies and (2) overall urinalysis-verified opiate- and cocaine-abstinence. Results: DWG and/or IWG reported improvements in several QOL areas (sleep, transportation, recreation); however, they also reported increased money-related difficulties and less time spent with friends/family. These changes did not coincide with DWG's work access, but some (more sleep, money-related difficulties) coincided with the urinalysis contingencies. Greater opiate- and/or cocaine-abstinence was also associated with several improvements: sleep, paying bills, time spent with friends/family, and exercising. Surprisingly, intermediate cocaine abstinence was associated with reductions in work-capacity satisfaction and recreation. Conclusions: Participants reported complex QOL differences during their experimental employment and associated with drug abstinence. Future work should help participants address issues that may be relevant to employment generally (e.g., time with friends/family) or contingency management specifically (e.g., money-related issues for non-abstinent participants).

Employment outcomes of substance use disorder patients enrolled in a therapeutic workplace intervention for drug abstinence and employment.

Poverty is common among people who have substance use disorder. The therapeutic workplace addresses some of the interrelated and chronic problems of poverty, such as unemployment, lack of education and job skills, and drug use. A prior controlled trial showed that the therapeutic workplace was effective in promoting drug abstinence and self-reported community employment in unemployed adults in medication-assisted treatment for opioid use disorder. The current study extends this research by providing a detailed and objective analysis of employment outcomes using objective data abstracted from participants' pay stubs. Secondary analyses examined the types and patterns of employment that participants (N = 44) obtained during the trial, and the extent to which participants gained and maintained financially sufficient employment. Although most participants had relatively long histories of unemployment and underemployment, many participants (n = 26; 59%) obtained employment at some point during the intervention. Most participants worked part time and were employed in low-wage jobs, however. The mean number of hours worked per week was 20.6 h (range 5.5 to 41.3 h per week) and the mean hourly pay was $11.00 per hour (range $9.00 to $15.50 per hour). The most common type of employment was in food preparation and serving-related occupations (e.g., waiters and waitresses, restaurant cooks, and fast food counter workers). Many participants (n = 17; 65%) maintained employment in these jobs over several weeks, while others (n = 9; 35%) were employed sporadically for short durations. Additional supports may be needed for some chronically unemployed adults with substance use disorder to promote consistent employment in well-paying jobs.

Financial incentives promote engagement in employment services for unemployed adults in treatment for opioid use disorder.

BACKGROUND: Promoting employment among unemployed adults with substance use disorder is a difficult challenge for which existing interventions have had limited effects. This study examined whether financial incentives could increase engagement in employment services for unemployed adults in treatment for opioid use disorder. METHODS: The study was conducted from 2014 to 2019 in Baltimore, MD. After a 3-month abstinence initiation and training period, participants (N = 91) were randomly assigned to a Control group or an Incentive group and were invited to work with an employment specialist to seek employment in a community job for 12 months. Participants assigned to the Control group (n = 47) did not receive incentives for working with the employment specialist. Participants assigned to the Incentive group (n = 44) could earn financial incentives for working with the employment specialist, but had to provide opiate- and cocaine-negative urine samples to maximize pay. RESULTS: Incentive participants attended the employment services and worked with the employment specialist on significantly more days than Control participants (41.8 % versus 1.1 % of days; OR = 40.42, 95 % CI = 32.46-48.38, p < .001), and for significantly more hours than Control participants (3.58 versus 1.25 h, on average; OR=2.34, 95 % CI=1.83-2.85, p < .001). Incentive participants were more likely to be retained than Control participants when analyses were based solely on attendance (HR=0.12, 95 % CI=0.06-0.25, p < .001) and attendance and employment combined (HR=0.15, 95 % CI=0.07-0.31, p < .001). CONCLUSIONS: Financial incentives were effective in promoting engagement in employment services for individuals who often do not utilize employment services.

Effects of incentives on viral suppression in people living with HIV who use cocaine or opiates.

BACKGROUND: Antiretroviral therapy (ART) adherence is essential to maintenance of undetectable viral loads among people living with HIV, which improves health and reduces HIV transmission. Despite these benefits, some people living with HIV do not maintain the level of adherence required to sustain an undetectable viral load. This problem is particularly common among people who use drugs. OBJECTIVE: To determine effects of incentivizing viral suppression in people living with HIV who used cocaine or opiates. METHODS: In this secondary analysis of data collected during a randomized controlled trial, participants (N=102) with detectable HIV viral loads (>200 copies/mL) were randomly assigned to a Usual Care or Incentive group. Usual Care participants did not earn incentives for viral suppression. Incentive participants earned incentives ($10/day maximum) for providing blood samples with reduced or undetectable (<200 copies/mL) viral loads. All participants completed assessments every three months. Results collected during the first year were compared based on group assignment and drug use. RESULTS: Among participants who used cocaine or opiates, Incentive participants (n = 27) provided more (OR:4.0, CI:1.6-10.3, p = .004) blood samples with an undetectable viral load (69 %) than Usual Care participants (n = 25; 41 %). Among participants who did not use cocaine or opiates, Incentive participants (n = 25) provided more (OR:4.1, CI:1.5-10.7, p = .005) blood samples with an undetectable viral load (78 %) than Usual Care participants (n = 25; 36 %). Effects of incentives did not differ by drug use (OR:1.0, CI:0.3-4.0, p = .992). CONCLUSIONS: Incentivizing viral suppression can promote undetectable viral loads in people living with HIV who use cocaine or opiates.

Effects of time-based administration of abstinence reinforcement targeting opiate and cocaine use.

Polydrug use is a common problem among patients in opioid-substitution treatment. Polydrug use has been reduced by administering abstinence-reinforcement contingencies in a sequence, such that a single drug is targeted until abstinence is achieved, and then an additional drug is targeted. The present study examined effects of administering abstinence-reinforcement contingencies sequentially based on time rather than on achieved abstinence. Participants accessed paid work (about $10/hr maximum) in the Therapeutic Workplace by providing urine samples 3 times per week. The urine samples were tested for opiates and cocaine. During an induction period, participants earned maximum pay independent of drug abstinence. Then, maximum pay depended upon urine samples that were negative for opiates. Two weeks later, maximum pay depended upon urine samples that were negative for both opiates and cocaine. Opiate and cocaine abstinence increased following administration of the respective contingencies. The time-based administration of abstinence reinforcement increased opiate and cocaine abstinence.