Behavioral factors predicting response to employment-based reinforcement of cocaine abstinence in methadone patients

Abstract

We sought to identify behavioral factors associated with response to an employment-based intervention, in which participants had to provide drug-free urine samples to gain access to paid employment. The present secondary analysis included data from a randomized clinical trial. The trial evaluated whether employment-based reinforcement could decrease cocaine use in community methadone patients. Participants (N=56) in the trial worked in a model workplace for 4 hr every weekday and earned about $10 per hr. After a 4-week baseline, participants were randomly assigned to an Abstinence & Work (n = 28) or Work Only (n = 28) condition and could work for an additional 26 weeks. Abstinence & Work participants had to provide cocaine-negative urine samples to work and maintain maximum pay. Work Only participants only had to work to earn pay. For Work Only participants, cocaine abstinence during baseline and the intervention period were significantly (r_s = .72, p <.001) correlated. For Abstinence & Work participants, baseline opiate abstinence was significantly correlated (r_s = .59, p <.001) and workplace attendance was marginally correlated (r_s = .32, p = .098) with cocaine abstinence during the intervention period. Furthermore, participants who provided over 60% cocaine-negative urine samples during the intervention period (i.e., responders) had significantly higher baseline rates of opiate abstinence (p <.0001) and workplace attendance (p = .042) than non-responders. Employment-based reinforcement of cocaine abstinence may be improved by increasing opiate abstinence and workplace attendance prior to initiating the cocaine-abstinence intervention.

Keywords: Cocaine; contingency management; incentives; methadone; opiates.

Figure 1

The relation between each of the three primary baseline measures (x-axes) and the percentage of cocaine-negative urine samples collected during the intervention period (y-axes) for the Work Only (left column; n=28) and the Abstinence & Work (right column; n=28) conditions. The filled circles show data from individual participants.

Figure 2

The percentage of cocaine-negative urine samples, opiate-negative urine samples, and minutes worked during baseline for Non-responders (n=22) and Responders (n=6) in the Abstinence & Work condition. Participants who provided cocaine-negative urine samples on more than 60% of the urine collection opportunities during the intervention period were categorized as Responders; all others were categorized as Non-responders. Filled circles represent individual participants and the grey horizontal lines represent group means.